Snow Threat Sunday-Monday - Middle Atlantic States

By: Pcroton , 12:08 AM GMT on March 14, 2014

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Update Section, March 16, 4PM

Afternoon analysis shows that the earlier model solutions showed the high pressure suppression as too strong and storm impacts have nudged northward through Central NJ.


Updates begin on Post #267







March 16, 8AM

Snow and Ice threatens the Middle Atlantic states while Severe Weather hits the Gulf Coast and Florida.

Updates Posts 228-233





Updates Posts 228-233






Blog Opening, March 13, 9PM

A potential snow storm threat exists for the Middle Atlantic States for Sunday into Monday.






Two pieces of energy will combine over the Southern Plains on Saturday.








Here are the 12Z Models from 3/13 - centered at 96hr time frame - 8AM Monday.





Notice the amount of energy we are dealing with of which the models have resolved strung out along the frontal system. These scenarios frequently change as guidance nears in on the event. It would be unwise to trust any model guidance at this distance. Recently we have been somewhere in the 48 to 72 hour window where guidance has locked in. This would be the Friday 12Z runs or perhaps Saturday 0Z runs.




Recently guidance has been struggling with storm systems due to the pattern changing and the split flow patterns in the 500MB layer. The result is wildly ranging model solutions both individually and as a group. Note how wild the pattern is through the Pacific and Western US/Canada. These multiple stream splits will undoubtedly give the models fits.






What we know is a system will enter the Southern Plains on Saturday bringing the chance of severe weather. How the storm tracks from here is in question at this time.








The HPC appears to be fairly interested in the threat.

HPC guidance through 8AM Monday.











The NAO is once again going to be near neutral timed with yet another storm threat. While we've never gotten the "strong negative NAO" we heard was coming most of the winter (and never did) there was always this little dip that coincided with our storm threats along the upper middle atlantic coast.







Taking a peek at the long term it appears the Pacific features that were driving our cold weather outbreaks has begun to break up.


The dominating North Pacific SST anomaly has been relaxing.







The PNA is heading negative.







Our jet stream will feature quite an amplified yet fast moving pattern resulting in quite the temperature roller coaster. No longer are we locked into a persistently strong East Pacific ridge and thus Eastern trough.









Looking ahead we appear to be remaining on the cool side although not nearly as brutal as before.







Here are your CFS2 Temperature and Precipitation Maps. It appears through at least April we will remain cool.


The weeklies:















April Monthly:






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Almost made it to freezing today!!
Member Since: February 10, 2014 Posts: 0 Comments: 540
Guys dont buy into any one model. No believable scenario yet where storm will go too far north or too south..let's have confidence it will come at us just right..either way its too early in the game to draw any conclusions
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ahhh,the joy of model watching this winter.Its enough to make one drink.I don't have much to worry up here in Mass.
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That is ok it just can't do like the last storm did when it was centered in on central NJ then we got like 3 inches and it all went south I'm afraid that is what is happening again. Noooo
Member Since: November 8, 2012 Posts: 0 Comments: 308
looks like cmc is dropping south too.
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The 12Z NAM sure doesn't miss the NYC metro area, gives us a good hit.
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Just saw that too, cooldogs13. But things can still change.
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P 12z gfs looks ok but looks like its keeps most of the heavy precip just to our south just like the last storm
Member Since: November 8, 2012 Posts: 0 Comments: 308
Quoting 47. Pcroton:
Good to see ya chime in Hoy and Peng.


Well, here's the 0Z CMC





And here is the latest Mount Holly forecast for me. Note the second low being reflected in the forecasting for Monday night into Tuesday morning. Dual low - longer event possible? Remember these are the worst to try to model/forecast. Will it be two lows. Will it be one consolidated system. Etc.


SUNDAY NIGHT
MOSTLY CLOUDY. SNOW LIKELY...MAINLY AFTER
MIDNIGHT. BREEZY WITH LOWS IN THE UPPER 20S. CHANCE OF SNOW
70 PERCENT.

MONDAY
SNOW LIKELY. BRISK WITH HIGHS IN THE LOWER 30S. CHANCE
OF SNOW 70 PERCENT.

MONDAY NIGHT
MOSTLY CLOUDY WITH SNOW LIKELY IN THE EVENING...
THEN PARTLY CLOUDY WITH A CHANCE OF SNOW AFTER MIDNIGHT. LOWS IN
THE MID 20S. CHANCE OF SNOW 60 PERCENT.

TUESDAY
PARTLY SUNNY. A CHANCE OF SNOW IN THE MORNING. HIGHS
IN THE UPPER 30S. CHANCE OF SNOW 50 PERCENT.
The CMC is just absolutely gorgeous right about now.
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Here's what I'm going to do this time around. I'm going to wait until it's all over and then read the forecasts, LOL. I love watching all of the chaos unfold but based on the last several storms I think trying to predict what's going to happen with all of the model uncertainty is just wearing me down. Last week I thought one more storm would be awesome but now I think I can take it our leave it. Snow Lovers unite - maybe the I don't care attitude will get you all some snow! Watch this one turn out to be the one that ends up being the perfect storm and becomes the blockbuster that we've been thinking would happen all winter! Here in NJ we have had our share of snow this winter but most of the big ones went to our north or to our south. What's the chances of this one being the last gasp for us? Only time will tell.... Would love to say I'm not going to be checking in on this P over the next two days (can't seem to stay away) but it's exhausting!
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Morning P/all,
Ive been lurking but P doesnt it seem temp wise we right on that 32 33 area for forecasted highs on monday. My gut if it snows even moderate its should accumulate rather quick even given this time of year? Just a wait and see if this a mid atlantic system again or does it ride up the coast. Def chatter now about monday.
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Member Since: September 26, 2011 Posts: 45 Comments: 7272
Well, here we go.








And where they will be in a day...





We have our disturbances plain to see. Now it's a matter of how the models handle the 500mb pattern from tomorrow morning onward. That is where the disagreements begin!


=========================
Morning Updates begin on Post #18
=========================


Member Since: September 26, 2011 Posts: 45 Comments: 7272
Quoting 48. tlawson48:
If nothing else, cold air will be present this time around. With the front going through Saturday and winds from the NW Sat night, anywhere that this storm comes together will have decent temps to support frozen pecip. Land areas to the north are buried in fresh snow and this will help to keep the temperatures from modifying. In the mountains the depths are approaching five feet (57 inches reported on the trail to Tuckerman Ravine).

I would kind of like a snowstorm in Southern Maine if only for the fact that if it goes south of us, it means three to four straight days of sub freezing temps with lows in the single digits (still mid January in mid March).


I think cold air will certainly exist for the overnights. During the day however marginal low 30s would mean melting accumulations.

As for you up north I don't think this affects you. You may get some snow showers from the frontal systems on Saturday and early Sunday? I don't see you getting in on these low pressure systems though. They're staying south.


Member Since: September 26, 2011 Posts: 45 Comments: 7272
500MB evolution. Two real nice disturbances to work with at the start. GFS strings out the energy resulting in the multiple disorganized lows. NAM consolidates and amplifies one strong system. Therein lies the differences. Major differences not really producing THAT wide spread of a model solution if you think about it.








Member Since: September 26, 2011 Posts: 45 Comments: 7272
If nothing else, cold air will be present this time around. With the front going through Saturday and winds from the NW Sat night, anywhere that this storm comes together will have decent temps to support frozen pecip. Land areas to the north are buried in fresh snow and this will help to keep the temperatures from modifying. In the mountains the depths are approaching five feet (57 inches reported on the trail to Tuckerman Ravine).

I would kind of like a snowstorm in Southern Maine if only for the fact that if it goes south of us, it means three to four straight days of sub freezing temps with lows in the single digits (still mid January in mid March).
Member Since: February 10, 2014 Posts: 0 Comments: 540
Good to see ya chime in Hoy and Peng.


Well, here's the 0Z CMC





And here is the latest Mount Holly forecast for me. Note the second low being reflected in the forecasting for Monday night into Tuesday morning. Dual low - longer event possible? Remember these are the worst to try to model/forecast. Will it be two lows. Will it be one consolidated system. Etc.


SUNDAY NIGHT
MOSTLY CLOUDY. SNOW LIKELY...MAINLY AFTER
MIDNIGHT. BREEZY WITH LOWS IN THE UPPER 20S. CHANCE OF SNOW
70 PERCENT.

MONDAY
SNOW LIKELY. BRISK WITH HIGHS IN THE LOWER 30S. CHANCE
OF SNOW 70 PERCENT.

MONDAY NIGHT
MOSTLY CLOUDY WITH SNOW LIKELY IN THE EVENING...
THEN PARTLY CLOUDY WITH A CHANCE OF SNOW AFTER MIDNIGHT. LOWS IN
THE MID 20S. CHANCE OF SNOW 60 PERCENT.

TUESDAY
PARTLY SUNNY. A CHANCE OF SNOW IN THE MORNING. HIGHS
IN THE UPPER 30S. CHANCE OF SNOW 50 PERCENT.
Member Since: September 26, 2011 Posts: 45 Comments: 7272
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P and All,
Kind of interesting on the drive to my office, a local weather radio met assigned to our area, mentioned that SWPA and SEOH as well as south of us and east of us, "somebody will see a good amount of snow 10-16" of heavy wet snow", although he did put the caveat out that we still have a couple of days to figure out. I will tell you this much and it comes from Henry Margusity who always says areas that get snow breed more snow, for my area we just have not received the big one although we have received way above average.

Lastly, it seems that Joe B, except for 1 storm has been dead on and way in front of everybody else, as well as Bernie from accu.

To All be Safe!!!
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Quoting 15. listenerVT:


We really need to invent a way to share snow, because I would be happy to send some. :-)


You don't have that app yet? ;)
Quite the storm you got up there, and some nice shots.

Numberwise said it well, P, and I agree. It's fun to ride the waves of possibility on this, as well as other, weather blogs.

As for the upcoming storm, P, that's correct, in my forecast it shows much of that storm occurring during the day. Says it will start late Sunday night and continue to early Monday night, with a total anywhere from 3-6." With it being as warm as it has been (excluding yesterday and the last two nights) as well as temps near 60 tomorrow, I doubt a lot of it will be sticking, especially as it's not a dumping of precipitation. I'd prefer if it doesn't happen at all, rather than make a slushy mess.

Member Since: January 20, 2009 Posts: 0 Comments: 1503
HPC track and WIDE ranging ensembles.





Ya gotta be kidding me that 48-60 hours from the onset of accumulating snowfall for DC to NY that they have this little of an idea and that wide of a envelope.


So let me get this right. With all I have read today I could:

*See 6-12" of snow
*Rain
*Sunny and cold


OK then. Wonderful. Glad they're on top of things here.



==============
Morning Updates begin Post 18
==============



Member Since: September 26, 2011 Posts: 45 Comments: 7272
Quoting 40. cooldogs13:
P what is the timing of this storm will we have the march sun to deal with or a cold night?


Looks like Sunday evening through Monday afternoon.

So we'll have both to deal with.

If you read Manahattan's forecast it sounds like they expect the heaviest snow during the day on Monday which for us would mean snow falls from the sky but struggles to accumulate in the daytime.

I think if we were to see good accumulations we need a decent hit overnight Sunday to lay down snowfall for Monday's to stick to. Even then the sun digs through the snow and starts to melt it from underneath.


It would seem given all the possibilities - and apparent wide ranging like and dislike for this storm - and the general dislike of the models we see - that nothing will be solved today in any way.

Tomorrow morning we should have a good idea. Today...throw a dart and live with the consequences I guess.

Member Since: September 26, 2011 Posts: 45 Comments: 7272
Sounds like the HPC hates both the NAM and GFS and are ignoring them.


Steve D hates the storm calling it weak, disorganized, and suppressed with a complete miss possible.


The HPC wording seems odd to me since the NWS apparently really likes the storm.


I guess today is yet another day of model guidance and multiple forecasting ideas being debated.


Maybe it's best to sit back and watch and wait for tomororow for any concrete ideas.

It sounds like nobody really knows - and there's people who are really high on the storm - and others who seem to want to make it disappear off the maps entirely if they could.

*shrug*

Member Since: September 26, 2011 Posts: 45 Comments: 7272
P what is the timing of this storm will we have the march sun to deal with or a cold night?
Member Since: November 8, 2012 Posts: 0 Comments: 308
The HPC take on the system.

====



...Middle ms-oh valleys/central appalachians/mid-atlantic...

A narrow but potentially significant swath of snow possibly mixed
with sleet and ice is expected to develop from southern missouri
into the ohio valley on sunday before expanding into the central
appalachians and mid-atlantic region sunday night and early
monday.

The nam was ruled out due to its fast solution relative
to the solution envelope while aspects of the gfs were also ruled
out particularly the precipitation associated with the lead
surface low approaching the appalachians that appears to be
augmented through convective grid-scale feedback.

Otherwise its
solution appears useful but is less than ideal. Presently prefer
the low tracks and their respective liquid equivalents and p-types
of the 12-00z ecmwf/00z ukmet/12z ecmwf ensemble mean the
most...With the 00z gfs/00z canadian offering some benefit as
well.

Farther east...Models appear to be coming
into better agreement with higher snow totals developing across
the central appalachians...Where some areas could receive 6 to 12
inches. Thus...Have high/moderate/low probabilities of 4/8/12
inches respectively in this area.

Conditions for heavy snow east
of the appalachians are less clear due to the uncertain role of
the northern stream/initially warm temperatures/growing solutions
spread. Thus...Preferred to adjust downward the direct model
output of some of the more aggressive solutions that suggest
totals in excess of 6 or even 8 inches near washington dc...Until
some of the factors contributing to the uncertainty are better
resolved.

Again...Preferred a solution somewhere between the
ecmwf/ukmet/ecmwf ensemble mean...With some downward adjustments
then made. The final result shows the highest snow probabilities
across the central appalachians...With moderate probabilities of 4
inches and low probabilities of 8 inches over washington dc.

A
narrow zone of slight probabilities of 0.25 inches of freezing
rain also accompany southern fringes of the snow over parts of the
ohio valley.
Member Since: September 26, 2011 Posts: 45 Comments: 7272
Quoting 36. noreasterrrrr:
That's interesting P..il try that from now on..but yea seeking a trend is good enough at this point ( although id like to think I have a chance at being in that 6-12 as well);)


You do and given guidance I could be 6-12" or I could be wet. We just don't know yet.


Quoting 35. trHUrrIXC5MMX:
Im happy you brought that up about the NAM... I read the 4 AM updated NYC wx discussion, they "dismissed" the so rejected NAM solution thus only calling for significant snowfall from NYC-Long Island on south

I think that's a no-no





However they mentioned tonight's 00z suite to hold the first keys to the event. But they believe on a more northern track


Clearly there is a lot to be worked out and I agree they shouldn't be yet dismissing guidance.

What they're doing is dismissing an outlier too early. NAM is an outlier to all other guidance which is fairly well centered on the GFS/Euro. Yet it did this with the last storm and proved to be on the right track and not an outlier.


I too believe tonight's 0Z may be the one to really "like" - but moreso in a supporting/confirming way of what we see with todays 0Z/12Z packages.

These models can drive you nuts.

You have to:

*Pick when the model trend is going too far (north north north(perfect spot but...) keep going north north on future runs)

*Pick when a drastic model change has caught onto the proper solution because something was finally sampled - or if it's an error run and to stick with previous guidance (NJ, NJ, NJ - Maine....)

By the time you get supporting run after supporting run and you decided "ok they have it" you've lost time forecasting because you couldn't trust the FIRST run or two when they showed the new drastically different solution.

That is what killed us with the storm that flew south into VA-MD-DE. The models snapped to that on the Friday but because it was such a drastic jump nobody wanted to follow that until later on Saturday.

Therein lies the true problems with these things. Guessing when you finally have the right run - when it's the first run of that solution - while awaiting confirming guidance from future runs.

It's a dart throwing experience which is why I always like to have an idea and then wait.



Member Since: September 26, 2011 Posts: 45 Comments: 7272
Tonights HPC product release will likely cover the entire event.

At present the HPC graphics in Post #18 only cover through 8AM Monday and therefore do not cover the whole event.

While these graphics work fine for say DC area - they do not for NJ-NYC and points north/east. The storm will still be ongoing at that hour.


Given that I think today's 12Z runs should be "fun" and the NWS/HPC products derived from them this evening could give us a much better picture.

Member Since: September 26, 2011 Posts: 45 Comments: 7272
That's interesting P..il try that from now on..but yea seeking a trend is good enough at this point ( although id like to think I have a chance at being in that 6-12 as well);)
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Im happy you brought that up about the NAM... I read the 4 AM updated NYC wx discussion, they "dismissed" the so rejected NAM solution thus only calling for significant snowfall from NYC-Long Island on south

I think that's a no-no


NAM AND SOME EARLIER RUNS OF THE CANADIAN HAVE EJECTED THE TROUGH WHOLESALE...
LEADING TO A MORE NORTHERLY AND SNOWIER SOLUTION FOR OUR REGION.
THINK THIS IS OVERDONE AND SIDED WITH A BLEND OF THE 00Z
GFS/ECMWF/CANADIAN...WHICH ARE IN BETTER AGREEMENT ON AN INITIAL
WAVE MOVING TO OUR SOUTH SUNDAY NIGHT-MON AHEAD OF THE MAIN TROUGH
AND BRINGING THE BULK OF ANY SNOWFALL DURING THAT TIME...WHILE A
STRONGER LOW ASSOCIATED WITH THE MAIN TROUGH REMAINS TO OUR SOUTH
LATE MON NIGHT INTO TUE.

IT WILL PROBABLY TAKE UNTIL THE 15/00Z FCST CYCLE TO BETTER SAMPLE
THE UPPER LEVEL FEATURES AS THE NRN STREAM SYSTEM ENTERS THE U.S.
RAOB NETWORK. THAT SAID...THE GENERAL MODEL TREND HAS BEEN A LITTLE
FARTHER NORTH AND WETTER.

However they mentioned tonight's 00z suite to hold the first keys to the event. But they believe on a more northern track
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Quoting 31. noreasterrrrr:
Well P everyone looks at these model runs in thier own way...for me when I look at it if we take the extreme north soultion..and the extreme southern soultion, then we average em both out, well I kinda see for my area and yours we can be in for a decent 4-8 storm. And for mid to late march...and missing the past few what could have been. This I would be greatful for and welcome it.


That's certainly a good way to look at it.

What I do at this stage is see it as a guidance envelope.

Presently the NAM is the northern edge, GFS southern edge.

What I then like to try to do is dismiss the northern most and southern most - as well as the driest and wettest models - and then average what is left.

OR other times try to pick and choose pieces of each model that make sense - such as - if I like the GFS track - and the NAM QPF so to speak - then I'll take that NAM snow output and visually put it over where the GFS has it's swath - and go with that idea.


All kinds of ways to look at these things.

At this point....seeking a trend....and then want to dismiss the outliers.

Member Since: September 26, 2011 Posts: 45 Comments: 7272
Here is that good twitter discussion regarding the models.


=====
Updates begin Post #18
=====


Member Since: September 26, 2011 Posts: 45 Comments: 7272
Quoting 27. trHUrrIXC5MMX:
no wearing the green... lol

I can't make out the map to the right which has the large snow swath... I know it's the NAM but the readings are too small...

that one could be exciting...


The scales are the same I think map to map in terms of accumulation scale. So that crazy NAM one would be 16" plus widespread.

I have a seriously hard time believing that one.




Quoting 28. trHUrrIXC5MMX:
GFS is a little south than NAM.
Lots of moisture to work with


The NAM was right with the last storm pushing the rain/snow line through Albany - and also having a strong dry slot presence through NJ-CT.

It was largely dismissed by forecasters and the HPC last time.

Does that mean it holds value with this storm? Who knows...but it means we shouldn't just ignore it either "Oh the nam" if you will.

I hope our 12Z runs don't fault and cause a wider spread in guidance and more questions.

It certainly looks exiciting though yet again and we're in Mid March now.

Given Mid-March - if we're low 30s for highs here in NJ and points south - and it's snow Monday - unless we got hit with a decent accumulation sunday night - then it's going to struggle to accumulate!

So this MUST be factored in when we look at all these maps.

Remember last March we had 2 systems that came through DC - stacked vertically for a few hours each - and then lost their lift and warmed. One system gave me an all-day snow event. At least 10-12" of snow fell from the sky. At it's peak? About an inch of slush formed on the grass.

Why? 34F and mid-march!

So....let's be careful there.

Upper 20s though like Manhattan is presently forecast? That WOULD accumulate probably 80% or so of what fell from the sky.


As to accumulations and the "nuclear nam" and such - I think at this time until we see otherwise you could say the storm has 6-12" potential.

Manhattan's forecast verifies that with the Light, Moderate, Light sequential forecasting.

Member Since: September 26, 2011 Posts: 45 Comments: 7272
Well P everyone looks at these model runs in thier own way...for me when I look at it if we take the extreme north soultion..and the extreme southern soultion, then we average em both out, well I kinda see for my area and yours we can be in for a decent 4-8 storm. And for mid to late march...and missing the past few what could have been. This I would be greatful for and welcome it.
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Ya'll just hating.Stop trying take mah snow!
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Gary Szatkowski ‏@GarySzatkowski

@oxlamb @nynjpaweather Just as I don't buy the 06Z/18Z model runs are inferior due to lack of radiosonde/upper air data.


Gary Szatkowski ‏@GarySzatkowski Mar 1

@oxlamb @nynjpaweather On the 00Z/12Z runs with upper air radiosonde data, GOES satellite soundings hold 60+/1 ratio for model ingest.


Gary Szatkowski ‏@GarySzatkowski

@nynjpaweather Oh, members of my staff believe the 06Z/18Z model inferiority argument. I don't.

Gary Szatkowski ‏@GarySzatkowski

@oxlamb @nynjpaweather Regarding sampling, as far as I'm concerned, its well sampled. I don't buy the 'it needs to be over land' argument.




Gary Szatkowski ‏@GarySzatkowski Mar 1

@oxlamb @nynjpaweather @mpierre19 Another good question, & answer is we do. Here are numbers. Satellite data accounts 88.7% data ingest.

Gary Szatkowski ‏@GarySzatkowski

@oxlamb @nynjpaweather @mpierre19 Other model data ingest numbers
Land - surface obs 4.2%
Marine surface obs - 1.4%
Aircraft obs - 5.6%!!


Gary Szatkowski ‏@GarySzatkowski Mar 1

@oxlamb @nynjpaweather @mpierre19 And those upper air observations we were 'discussing'. 0.1% If I've done my math right, that totals 100%
Member Since: September 26, 2011 Posts: 45 Comments: 7272
GFS is a little south than NAM.
Lots of moisture to work with
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no wearing the green... lol

I can't make out the map to the right which has the large snow swath... I know it's the NAM but the readings are too small...

that one could be exciting...
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Gary S in another rare form moment with a back and forth:






Joe B from yesterday seems to have been on point:







Today Joe tweet:


Member Since: September 26, 2011 Posts: 45 Comments: 7272
As always never get attached to any model run at this point. We're just viewing the possibilities for this storm system.


6Z Runs....which one should always be wary of at this distance from the onset of a storm....as they don't incorporate soundings - but at this time - the disturbances arent well sampled anyway - so what's the harm.

NAM really wants to head north and is extremely wet. Curious to see if 12Z continues this trend or not which is partly why I am posting these. If anything this illustrates what would happen if the storm did go north - showing those in DC and NJ the possibilities that exist with this storm. I would think this run really demonstrates the farthest north this system could possible run given the pattern and flow. I think it's too far north and way too wet. Maybe followup guidane supports this and maybe not - but at this time it's a trail blazer and we all know how I feel about that first model to take a plunge....don't like following it like a blind puppy!







The GFS has held basically firm but is a little north all the same than it's 0Z run.







An interesting debate occurred between Steve D and Gary S of Mount Holly on the value of off-hour model runs. Steve detests them and cites the upper air data. Gary S said there's nothing wrong with the runs and that Soundings are only 1%, yes 1%, of the model input - and the majority of model data input comes from Satellites.

I will try to dig up his post about that - but it was so long ago.




Morning Updates begin Post #18
Member Since: September 26, 2011 Posts: 45 Comments: 7272
We can look at the present 500mb setup and it's 24 and 48 hour forecasts. If anything to post these maps because they're still cool.










============
Morning Updates begin Post #18
============


Member Since: September 26, 2011 Posts: 45 Comments: 7272
I think Washington DC snow lovers should hold on to some tempered enthusiasm at this time for if you read all discussions it sounds like a further north and warmer trend may affect the region.

If you took Mount Holly's discussion at face value you would expect DC to be a slush storm at best.

Therein lies a bit of a problem in forecasting for it's as if all three WFO offices are writing the same thing for their respective regions.

So if Upton is correct about further north - then that means Mt Holly gets a mix and DC gets a slush or rain.


Apparently they all see the same thing - but - they all seem to halt that "further north" solution on each of their respective doorsteps.

One thing to look at is how Mount Holly discusses that the split flow pattern is going to resolve itself and become amplified - this means further north track - and that would begin to threaten DC's potential here.

They dismissed the NAM's further north/warmer solution for the Westchester-Albany corridor with the last storm - and if you recall we discussed how that corridor was the border zone and could see forecast problems - and in the end the NAM prevailed over all guidance for that region.

So to see the NAM once again start pushing that - maybe we should be a little more careful here in what to expect - and not just pencil in DC for 6" of snow and NYC for a dry inch.

It seems like the trend is more amplified and further north.

We'll see what 12Z guidance brings before digging into the pattern and the thermal boundaries and whatnot - because I think the 12Z will be a better suite than the present 0Z to put that kind of work into.

Of course every time I think the next guidance package will be better is when these damn things decided to go all over the place on the map.

Member Since: September 26, 2011 Posts: 45 Comments: 7272
Washington DC Discussion:


Frontal boundary stalls out across southern virginia saturday night.
Complex pattern then unfolds sunday into monday. Behind the front
and with high pressure building in from the north...Colder air will
push southward into the mid-atlantic with the models indicating a
cold air damming wedge developing. At the same time...Potent
shortwave ejecting out of texas shifts into the lower mississippi
river valley.

Moisture will begin to overrun the frontal boundary as early as
sunday first translating to thickening clouds and then
precipitation. Boundary layer may be warm enough at the onset for
rain or a rain/snow mix sunday...But most guidance suggests colder
air supporting a changeover to snow sunday night. The nam is an
exception which favors a warmer solution /at least in some areas/ but
prefer a blend of deterministic/ensemble ecmwf and gfs solutions
and more frozen precipitation.

Main thrust of precipitation due to overrunning/isentropic lift
occurs sunday night into early monday...With models indicating one
wave of low pressure forming off the coast by 12z mon. Another low
further south tied to the upper level system will be in play as
well for monday...However latest models are trending on tracking
this more east than northeast but there is some uncertainty with
this track.

Will obviously need to fine tune the details of this complex pattern
as we get closer...But confidence is increasing in a period of snow
across the majority of the cwa sunday night into monday and
continues to be advertised in the hwo.





Mount Holly Discussion:


What was originally a split flow becomes more amplified with a
building ridge across the western united states making for a better
defined trough downstream and northwest pacific energy diving down
deep into the southern u.S. Depending on how strong this energy
eventually becomes/is and how fast it phases with its southern
stream counterpart would ultimately dictate where the mid-level
troughing sharpens/deepens and where the surface low would track.
The past several days have kept a majority of the mid-level energy
to our south though a northward trend has been seen with the past
several runs of the mid-range guidance. The ensembles members off
both the gefs and ec have shown the most noise/spread to the north
of the surface feature giving more credence to a northward jog. The
northward jog is two fold with more moisture traversing the region
and also a tighter thermal gradient across at least our southern
zones at this point in time.

For the most part the northern half of the region will be cold
enough for all frozen precipitation with a cold dome in place. Down
south, if the north trend continues, would see a changeover to snow
as the system moves further away from the region. Guidance is
showing a warmer layer around 800-850mb which could move pretty far
northwest giving way to more of a mix-bag across the southern half
which would greatly cut-down on the potential for an accumulating
snowfall.

At this stage in the game, confidence is increasing of a coastal low
affecting the region late sunday night through a better portion of
monday...The signals are there for it. Specifics about p-type and
accumulation amounts still need to be ironed out but we have plenty of time
for that as the northwest pacific energy has yet to come
onshore...Just a matter of time.





Upton Discussion:

The long term period looks to be fairly active with a transition to
a more progressive pattern across the lower 48. Most interesting
aspect of the forecast period remains sunday night through tue as a
wave of low pressure passes to our south. Uncertainty centers around
degree of phasing of a srn stream cutoff low over the southwestern
states attm with a shortwave trough moving onshore the pac nw today.
Degree of phasing of these two features...And ejection of shortwave
energy from this trough and the eventual progression of the trough
itself...Will determine eventual impacts to the area. Nam and some
earlier runs of the canadian have ejected the trough wholesale...
Leading to a more northerly and snowier solution for our region.
Think this is overdone and sided with a blend of the 00z
gfs/ecmwf/canadian...Which are in better agreement on an initial
wave moving to our south sunday night-mon ahead of the main trough
and bringing the bulk of any snowfall during that time...While a
stronger low associated with the main trough remains to our south
late mon night into tue.

It will probably take until the 15/00z fcst cycle to better sample
the upper level features as the nrn stream system enters the u.S.
Raob network. That said...The general model trend has been a little
farther north and wetter.
Member Since: September 26, 2011 Posts: 45 Comments: 7272
Mount Holly has really gone for it... for Central NJ


SUNDAY NIGHT
MOSTLY CLOUDY. SNOW LIKELY...MAINLY AFTER
MIDNIGHT. BREEZY WITH LOWS IN THE UPPER 20S. CHANCE OF SNOW
70 PERCENT.

MONDAY
SNOW LIKELY. BRISK WITH HIGHS IN THE LOWER 30S. CHANCE
OF SNOW 70 PERCENT.

MONDAY NIGHT
MOSTLY CLOUDY WITH SNOW LIKELY IN THE EVENING...
THEN PARTLY CLOUDY WITH A CHANCE OF SNOW AFTER MIDNIGHT. LOWS IN
THE MID 20S. CHANCE OF SNOW 60 PERCENT.





UPTON
is really into it, citing Light, Moderate, Light accumulations. 1-3, 4-6, 1-3 = 6-12" !!!!




SUNDAY NIGHT
CLOUDY. SNOW LIKELY...MAINLY AFTER MIDNIGHT. LIGHT
SNOW ACCUMULATION POSSIBLE. LOWS IN THE LOWER 20S. CHANCE OF SNOW
60 PERCENT.

MONDAY
SNOW LIKELY. ADDITIONAL MODERATE SNOW ACCUMULATION
POSSIBLE. COLD WITH HIGHS IN THE UPPER 20S. CHANCE OF SNOW
60 PERCENT.

MONDAY NIGHT
MOSTLY CLOUDY. LIGHT SNOW LIKELY IN THE EVENING.
ADDITIONAL LIGHT SNOW ACCUMULATION POSSIBLE. LOWS IN THE MID 20S.
CHANCE OF SNOW 60 PERCENT.
Member Since: September 26, 2011 Posts: 45 Comments: 7272
We have a fire threat throughout the region today. Those winds dried us out in a big way.




THERE IS AN ENHANCED FIRE THREAT FOR SPREAD AND GROWTH TODAY WITH
GUSTY SOUTHERLY WINDS AND LOW RELATIVE HUMIDITY.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

A COASTAL LOW PRESSURE MAY AFFECT THE REGION WITH WINTRY PRECIPITATION
SUNDAY NIGHT THROUGH MONDAY.





Member Since: September 26, 2011 Posts: 45 Comments: 7272
Quoting 8. PhillySnow:
Love your spirit, P! I totally agree, and I wasn't agreeing with that part of what he wrote. I just like the way he looks at and explains atmospheric conditions.


Oh I agree he is one of the best, if not the best, when it comes to presentation.


Quoting 9. HeavySnow:
WU forecast at this point has me in Annandale, VA at 4-8 inches of snow Sun night and Monday. HA!


Awesome. I like it. I would be a little wary at this time to see whether or not we see further jogs northward - but there is only so far north this system can go. Present NAM leaves you guys around DC out of this but it appears forecasters are ignoring that for now. Unfortunately they ignored the NAM with the last storm which had the correct far north rain/snow lines - so we'll see how it goes.


Quoting 10. NumberWise:
Pcroton: Hope you enjoy the new blog entry.

Ha! We all enjoy all the blog entries - obviously! Whether or not a storm materializes, underperforms, or overperforms, the puzzle of following its development seems to be what fascinates us. Your maps, charts, analysis, and opinions help us to follow what is happening. I, for one, appreciate the time and effort you devote to your hobby and generously share with us.

Yeah, we know you're a hobbyist, not a professional. We know your thoughts are personal opinions, not professional forecasts. We know that you editorialize, and that's precisely why we keep reading your blog.

Pat on the back. Thanks.



I appreciate it. True the tracking is a fascinating aspect of the weather.


Quoting 11. noreasterrrrr:
P lee goldberg just said on 11pm news that evidence getting stronger for accumulating snow monday into nyc..stsy tuned for details. Well at least seems like we are heading in right direction


I think it's possible. We need to watch and see just how far north this system gets. Probably won't have the best handle on things today - best for Saturday for that.


Quoting 13. listenerVT:
Pcroton…
I'm supposed to travel down to Concord, NH for meetings on Monday. Bad idea?


Awesome photos. My birds are confused as well. They were digging up worms, enjoying the clean bird baths, and then we froze back over again.


As to travel I'd just wait and see at this point - it looks like this storm system can only get so far north - and whatever snows you get further north are from a northern stream disturbance and not the middle atlantic storm low. We will watch it through the course of the day but at this time (famous last words) it does not appear this system will reach much further north than the southern coastline of New England.


Quoting 17. tlawson48:
Local NWS is a little gun shy after the last storm as they have zero mention of any chance of precipitation on Mon. No mention in the dailies and no mention in the forecast discussion, in fact they don't even mention clouds...



I don't believe this low is going to affect you. It's got a more East North East track from the Middle Atlantic. What you get is the same as Listener - some northern disturbance with maybe some very light snow.

Quoting 14. NatsFan:
ListenerVT:

Great photos! I am soooo jealous of that snow. I want some.


Could be some snow from this in DC-Baltimore regions...I forget where you are located though.

Member Since: September 26, 2011 Posts: 45 Comments: 7272
Looks like we have an upper middle atlantic storm system.























Member Since: September 26, 2011 Posts: 45 Comments: 7272
Local NWS is a little gun shy after the last storm as they have zero mention of any chance of precipitation on Mon. No mention in the dailies and no mention in the forecast discussion, in fact they don't even mention clouds...
Member Since: February 10, 2014 Posts: 0 Comments: 540
Quoting 10. NumberWise:
Pcroton: Hope you enjoy the new blog entry.

Ha! We all enjoy all the blog entries - obviously! Whether or not a storm materializes, underperforms, or overperforms, the puzzle of following its development seems to be what fascinates us. Your maps, charts, analysis, and opinions help us to follow what is happening. I, for one, appreciate the time and effort you devote to your hobby and generously share with us.

Yeah, we know you're a hobbyist, not a professional. We know your thoughts are personal opinions, not professional forecasts. We know that you editorialize, and that's precisely why we keep reading your blog.

Pat on the back. Thanks.
Well-said, NumberWise. Ditto!
Member Since: December 18, 2009 Posts: 0 Comments: 1231
Quoting 14. NatsFan:
ListenerVT:

Great photos! I am soooo jealous of that snow. I want some.


We really need to invent a way to share snow, because I would be happy to send some. :-)
Member Since: July 11, 2007 Posts: 0 Comments: 5484
ListenerVT:

Great photos! I am soooo jealous of that snow. I want some.
Member Since: October 29, 2012 Posts: 0 Comments: 33
Pcroton…
I'm supposed to travel down to Concord, NH for meetings on Monday. Bad idea?
Member Since: July 11, 2007 Posts: 0 Comments: 5484

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About Pcroton

Located in Monmouth County in central NJ. Watching the weather from North Carolina to Maine.