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 10 inches in Annandale, VA! Nice!
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Quoting 361. KEEPEROFTHEGATE:
lifting ever slowly north by north east


Emphasis on the word "ever".
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lifting ever slowly north by north east
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Snowing hard in Springfield VA now. It's finally sticking to the roads. The cars have about an inch and a half on them. Not as much on the grass--ground is warm enough that it's still melting underneath.
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yea no surprise either way it goes
if we get it it will come from that surge in west virginia and cent maryland
dewpoints real low so the lesser echoes wont reach surface for a long time
most guidance didnt show accumulations for philly to cent nj until after 1-2am
Member Since: September 26, 2011 Posts: 55 Comments: 8649
29.9F here. Nothing falling from the sky, although radar has had us in snow for hours now. Still looks like it's coming this way, and we'll see. I also won't be surprised to wake up to nothing.
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It's progressing through NJ.





Until the morning....enjoy.

Member Since: September 26, 2011 Posts: 55 Comments: 8649
Mount Holly did incidentally tweak amounts yet again:




That's about as good as we're going to get for tonight I would think.

We have the radars and satellite imagery to watch so I think guidance at this point is getting useless.

And at this point it's about seeing what we have in the morning in the end.

Since the start when this looked like a March 3rd repeat I figured I'd get around the same 3" I got then.

We will see what the morning holds.

Member Since: September 26, 2011 Posts: 55 Comments: 8649
Quoting 349. Matlack:
P - the gulf moisture died - look at the WV as the moisture appears to be drying south to north. And radar is showing the normal NJ dry hole. Low confidence in the 3" and no way Mt. Holly comes close to the 4"-6" map here.



The NJ dry hole radar thing is an issue with the radar more than anything. Check the composites out they show a different story there. I've always wondered about that weird dry hole effect at the onset of every storm. Ever notice how it's always a perfect ring around the dix radar site? I think that's more a radar problem than an actual precip situation.


The low center has punched it's dry slot in but that's an expected process due to the 850/700MB low development.


850MB:




700MB:






Our snowfall is going to be a product of frontogenesis and lift versus the potential sinking air from the high.


850MB Frontogenesis:



The heaviest snows will be under the heavier values.


We have enough vapor remember we're not looking at a major storm and high qpf values reliant on a pipeline of moisture. It's just a moderate event.







Seems to be decent lift showing on the IR - and increasing over WV towards the PA border.






In the end this is going to be about the suppression from the high and all guidance shows the precip advancing then stalling then advancing then stalling as it moves into our area over the nighttime hours so we shouldn't get too attached to any period of radar imagery.

I think we have to look at the extended imagery over 3 hours or more to see the full range of the transport of moisture.


Note the surges in WV and in western NC on vapor:



If that makes it into our region, and it probably will, it will be enough.


Note the lift developing in the same areas and the motion.




I still think it looks pretty good here.




Whether or not we meet any particular forecast amount? That's always a crapshoot. We just don't know. It's why in the back of my mind I've always had myself in the 0-5" range. Just don't know in the end.




Member Since: September 26, 2011 Posts: 55 Comments: 8649
And just as I check back HRRR resumed at 22z.

From what I've heard this guidance isn't too good past 6 or 8 hours. I've also seen it fault outright just a couple hours into the runs. It's still considered an experimental product.


Here is the hourly snowfall rates at 12am, 4am, and 8am:









Here is the accumulated snowfall total:

Member Since: September 26, 2011 Posts: 55 Comments: 8649
P - the gulf moisture died - look at the WV as the moisture appears to be drying south to north. And radar is showing the normal NJ dry hole. Low confidence in the 3" and no way Mt. Holly comes close to the 4"-6" map here.
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Quoting 346. BaltimoreBrian:
Temperature down from 32.9 to 30.6 in last 50 minutes. A good inch+ on sidewalks and sticking to the streets! I'm impressed!


That is cool. Wow. Figured it'd take a little more to stick to the streets but you're on your way. Still, as it accumulates on top it still melts a little from underneath as you go. Still...impressive temp drop for sure.

Quoting 345. wxgeek723:
Snow has commenced down the shore. Still a defiant wait up here.

GSP @ Great Egg Toll Plaza - Somers Point


Our northern surge in New Jersey really isn't expected until around 1am or so according to the last HRRR guidance. When you watch radars look at central Maryland and note the surge northward to the PA border there the past hour. Envision that continuing and sliding ENE as it does - and I think that's where it comes from.

With the battle of dry air we may see these surges north and then halts then another surge and halt on and off as we get snow bursts on the edges.

Overall the whole system is moving though and should overcome it. It's just that it's unlikely to slide through all in one steady motion is all.

Member Since: September 26, 2011 Posts: 55 Comments: 8649
I believe NWS forecasting takes into account melting when posting accumulations.

As for starting as snow instead of rain in the south it's interesting but since surfaces are warm I am not sure how much more that would add to any particular totals.

I think since we've been so warm we need to drop to say 28F and/or have persistent heavy snowfall to see the forecast accumulations on the roadways when we awake. Also treatments will knock that down as well.



As far as how far north this thing will push it's questionable even at this hour.

I am noticing the first real significant moisture surge occurring in northern Maryland now:



Curious to see if that's a real solid push that will continue northward and then pull ENE.

I think NWS Mount Holly does have a decent handle on things. Anything north of I95 in central NJ is a 0-2" zone I would think be it Westchester or NYC or Newark NJ.

Is it just flurries, is it a dusting/coating, do you surprise up to 2"? Honestly we won't know until the overnight hours - which means - not until we awake and see what's going on with the radars and observations.


Unfortunately short range HRRR guidance has not updated since 19Z.

SREF model is still on 15Z, next cycle is 3Z and probably not out until Midnight or later.

So we're screwed on the short range.



The last SREF output was earlier today 15Z Cycle:




The last HRRR is posted above Post 317-318 and only goes out to 3am.

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Temperature down from 32.9 to 30.6 in last 50 minutes. A good inch+ on sidewalks and sticking to the streets! I'm impressed!
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Snow has commenced down the shore. Still a defiant wait up here.

GSP @ Great Egg Toll Plaza - Somers Point
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Quoting 342. LongbranchWX:
For what it is worth, It has been snowing in the Annandale/Burke/Fairfax City (No. VA) area for a bit over an hour or so and it starting to stick to the grassy areas/decks.

I think more interesting is that it started as snow, not rain and at my house the temperature is 31.3F while the forecast had us at 37F by 9pm and not hitting freezing till 1 AM. Do you think this means we are on track to get the higher side of the predicted snowfall? We are still going to spend a lot of time melting snow on the roads before they cool enough to let it stick, but being below freezing already must help.

Yes.This is ahead of schedule for sure.We were suppose to be in the rain transitioning to snow period.I was surprised to see it starting as all snow.
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P when will the snow make it to the coast? Cuz one it does then itl be snowing here a bit too based on movement
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For what it is worth, It has been snowing in the Annandale/Burke/Fairfax City (No. VA) area for a bit over an hour or so and it starting to stick to the grassy areas/decks.

I think more interesting is that it started as snow, not rain and at my house the temperature is 31.3F while the forecast had us at 37F by 9pm and not hitting freezing till 1 AM. Do you think this means we are on track to get the higher side of the predicted snowfall? We are still going to spend a lot of time melting snow on the roads before they cool enough to let it stick, but being below freezing already must help.

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Member Since: September 26, 2011 Posts: 55 Comments: 8649
It's snowing moderately right now in Springfield VA. Been snowing for 45 mins. The cars and grass are covered. Not sticking to the roads yet.
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Appreciate it, weathernewbie. Enjoy!


Champ, you've been really really cold this winter. Seems like you were always chiming in with sub zero mornings.


Doom, temps are dropping due to many situations including evaporative cooling, the sun going down, cold air filtering in from the north, and from aloft.


Philly I think you will do okay it's just going to be a slow drive is all.



Well, the high is certainly losing intensity. Note the pressure drops are pretty high right under it. Also note the low pressure trough point north and east from the mid-south low.




All the promising things we've watched all day are coming together to put SE Pennsylvania into Central NJ into the higher accumulating snows of 3" plus.


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Hello Pcroton! I noticed Phillysnow's post in the activity stream, and saw this blog. I've been a quiet-but-enthusiastic "Blizz" follower and found your posts there very helpful. I'm so happy for Zack's exciting news at school, and glad to see that you are sharing your weather expertise at WU!
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It's freaking cold here. I can't wait for march and warmer weather!!!
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In the past 2.5 hours we've had very light snow, gradually picking up. Some big flakes mixing in. Temperature has dropped from 40F all the way to 33F, here at the surface. I guess I am unsure whether the temperature drop is due to coolth being transported down from above by the precip, or whether the drop is due to the high pressure advancing.

And in that time, the barometer is down by .03, to 29.97 inhg.

Looks like DC is following the script.
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Thanks! They haven't treated the roads yet - who would given the models to date? I suspect the salt trucks will be out tonight, though; they've been pretty good with it.

Always an adventure!
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Quoting 333. PhillySnow:
I got on the computer only to check in and enjoy people's snow and imagine my surprise to see we're now forecast for 2-4" and the radar shows that storm coming our way! We'll see if it actually happens. :) 32.6F currently.

P - Being that the moderate snow is now coming at night, are we still assuming it won't stick much to the roads? Believe it or not, I've got to drive into the city at 5:00am tomorrow......


I think it will stick if you're significantly below freezing and the roads are not treated.

Aside from being a nuisance and slippery I don't see any actual travel problems here unless we all completely pooped the bed and you awake to 4-5" and it coming down hard.

I think you and I are in a 3-5" potential here.

All the discussion of earlier seems to now be realized.
Member Since: September 26, 2011 Posts: 55 Comments: 8649
I got on the computer only to check in and enjoy people's snow and imagine my surprise to see we're now forecast for 2-4" and the radar shows that storm coming our way! We'll see if it actually happens. :) 32.6F currently.

P - Being that the moderate snow is now coming at night, are we still assuming it won't stick much to the roads? Believe it or not, I've got to drive into the city at 5:00am tomorrow......
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Steve....really fighting this to the end here I guess.

===
Steven DiMartino ‏@nynjpaweather 18m

Well, so far based on the radar, precipitation is attempting to push north. So far failing.
===



????

Well, I guess he has his reasons and he's pretty good at what he does.

I don't share his opinion though.



Member Since: September 26, 2011 Posts: 55 Comments: 8649
Quoting 330. noreasterrrrr:
P i really think im i may get 2 or 3" here


According to the HPC products there's a chance albeit low (90th precentile). Here's the 3 layers in a row:










50th Percentile seems to generally match NWS forecasts. 90th percentile is frequently posted by Gary S as "Maximum Reasonable Worst Case Scenario".

Member Since: September 26, 2011 Posts: 55 Comments: 8649
P i really think im i may get 2 or 3" here
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Evening, Keep.


Well, and there it is on that radar. Echoes breaking out in PA in the area that was once sinking air - clearly now rising.

Also the orientation of the echoes clearly showing a direction that puts central NJ into accumulating snowfalls.

Fun watching the progression today.


Surface, 850mb, and 700mb levels (all in succession). Surface low boundary pointing ENE and that continues to be north of previous guidance/hpc. 850/700mb lows expanding and moving NE and as such inhibiting factors aloft in southern PA/NJ will also be moving ENE out of the region.

5PM MAPS:








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Latest HPC product issued: Hazards beginning at 5PM tonight:

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Look at the vapor rocketing SW to NE through KY-TN-OH



Look at the moisture cutoff approaching Chicago from the NW - also a SW to NE orientation line.

It looks like there's enough there to get Philly to Central NJ in the 3-5" range maximums.

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Quoting 323. Pcroton:


Didn't you just almost hit 80 on the days we hit 70 here?

But yeah this is dragging on.


Stronger radar echoes developing and moving towards Philly and central NJ







DelMarVa echoes deepening.



Nope.Thanks to cloud cover and over cast 70 was all we hit.
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Quoting 322. washingtonian115:
Spring is no where to be found.I have forgotten what 80's feel like.


Didn't you just almost hit 80 on the days we hit 70 here?

But yeah this is dragging on.


Stronger radar echoes developing and moving towards Philly and central NJ







DelMarVa echoes deepening.



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Quoting 319. Pcroton:
LOL geez...





Spring is no where to be found.I have forgotten what 80's feel like.
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Quoting 320. noreasterrrrr:
Wow P thats coooollld enough air id say for end of march to be frozen precip..just need a night storm now.


True. Only thing is the same zonal pattern that features suppression that could kill off chances.



Well now we know why the 18Z GFS came in a little more suppressed. It got the features wrong. High too strong, low too weak.




Funny how sensitive the whole thing is if one feature is modeled just 2mb off of actual. The whole thing goes in the tank in border zones.

Member Since: September 26, 2011 Posts: 55 Comments: 8649
Wow P thats coooollld enough air id say for end of march to be frozen precip..just need a night storm now.
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LOL geez...





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HRRR Total Accumulation through 3AM



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Moisture aloft pushed quite far north today on vapor imagery.




Over in Wisconsin you can see where the dry air finally pushed SE but that's too late to prevent the northern shift in accumulation potential in SE PA into central NJ that has increased.



18Z GFS is running. It cut off in central NJ like the 18Z NAM does - so we seem to now have a similar consensus among the two for a change.






Well, we have one last meaningful cycle of guidance really. 0Z tonight. After that it's all a NOWCast.




HRRR snowfall rates for midnight and 3am (end of guidance run).







Member Since: September 26, 2011 Posts: 55 Comments: 8649
Windy along the coastlines tonight. Especially southern NJ into DE and Maryland. 35-50mph.




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Latest release by Gary S.


Looks pretty spot on to me.
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Dewpoints are low but the 700mb level snow growth zone RH has gone up.






It will take some time to overcome the surface dry air. That is all incorporated into the modeling and forecasting.

Member Since: September 26, 2011 Posts: 55 Comments: 8649
Quoting 311. doom22015:
We must have a big-time virga thing going here in DC area. For some time, the radar has made it look like we should be getting lotsa snow, but nothing here at ground level. Guess this would be a good time to bring in firewood.
Temp is 40F and barometer is at 30.00 steady. I am ready to see both of those numbers falling!


Temps will drop and precip will increase through the evening and overnight. You could easily start as rain before going over. It's coming though.



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About Pcroton

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