North East and Mid Atlantic Weather

Severe Ice and Snow Storm Central Plains to Middle Atlantic

By: Pcroton, 11:57 PM GMT on February 26, 2014

March 3

The winter storm continues to affect the central and southern middle atlantic states this morning.

Updates being on Post #844








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Evening Update 3/2 9PM


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Updates Begin on Post #783
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Good Evening. The southern trends of forecasting continue. A moderate snowfall event begins in central NJ and becomes heavier as you head south. Jackpot regions appear to be situated in northern Virginia and Maryland.

A significant ice and snow threat continues for the central and southern plains through the Ohio and Tennessee valley regions into the Middle Atlantic states.


Monday's HPC Hazards:





Maximum Reasonable Accumulation Potentials:






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Blog Opening 2/26

A long duration winter weather event is in store for the Eastern United States spanning from the south central plains into the upper middle atlantic states.

A strong storm system north of Hawaii will head into the California coast line Friday into Saturday.








The system will head into the south central plains and send multiple areas of low pressure up a developing thermal gradient.




The tightly packed nature of the large thermal gradient leads to a lot of uncertainty down stream along the East coast in terms of PType and PType duration. A slight shift in storm track would result in dramatic changes for many locations. The extremely tight nature of this large thermal gradient will make fine details a near impossibility for many of us until the final day prior to the onset of the event.


Each low that moves along the stationary frontal system will first push some warm air into the border regions ahead of it and then pull cold air in behind as it exits.



This will cause many border regions to experience a roller coaster of PType from snow to mix to rain to mix to snow to mix to rain to mix to snow.

Each successive wave of low pressure should pull the frontal boundary further south as the event moves forward thus giving increasing chances of frozen precip in the border zones.

The current 12Z GFS paints what would be considered a perfect scenario at the 500mb pattern for the Philly to New York City corridor to receive a signifcant snowfall event. In order for the present 12Z GFS or the 0Z Euro model of 2/26 to pan out the following disturbances must be found in these locations shown below.




Then we would see the following transpire at the 500mb level.





Which would lead to near perfection in storm formation and track which could result in something of this nature. The following map is not a forecast but is a good illustration of this storm system's potential if all comes together correctly.





The timing of the sub-tropical and polar disturbances will be cruicial in what transpires along the eastern seaboard.





Todays 0Z and 12Z European Model runs show what might occur given an earlier or later phasing of the two streams. The following maps are not forecasts but can be used to illustrate the storm potential.





Regardless of exactly how the system phases and where the thermal boundary lines up this appears to be a significant long duration event for the region as illustrated by the 12Z GFS run. Models have been showing a system that will be lasting from 48 hours to as long as 60 hours.





Above all remember the models do not drive the weather and any personal emotion should not play into which model you prefer. Do not get attached to any one model run NOR any NEWEST model run until we draw closer to the event. At this far out the newest run doesn't automatically succeed the previous - these runs are initializing off of poor data and will continue to spit out differing solutions. Use them as a loose guide.

At this point we know a large long duration storm event with varied high impact weather will be affecting the region Sunday through Tuesday. Who gets what, when, and for how long is still yet unknown.

Winter Weather

Updated: 11:27 AM GMT on March 03, 2014

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Light Snow Event, Return of Cold, Stormy open to March

By: Pcroton, 10:25 AM GMT on February 24, 2014

2/26

Updates begin post #93.

Here is the storm system we will be tracking for the Sunday-Tuesday event.



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2/25 Afternoon

Continuing to track our weak Wednesday morning system. Keeping an eye on the March 3-4 time frame.

Updates begin Post #35.

HPC Hazards Map for Wednesday 2/26:



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2/25 Morning

Our Wednesday storm has quickly degenerated into a snow shower event.

Updates on Post #24






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Spring time is near but it won't come easy. A Light snow event will begin late Tuesday night lasting into Wednesday Morning for the central and upper middle Atlantic region, Cape Cod, and Eastern Maine.






The 500mb pattern does not support a more significant event. A broad trough has a strong west to east flow through the region. As a result the storm will slide off the coastline limiting our QPF potential.











All model guidance is in agreement here that the connection between the polar and sub tropical energy will be limited.













Snowfall potential will be limited. I would probably follow the GFS here but I do like to show all guidance. There could still be minor tweaks as we near the event but at worst this would raise some moderate snowfall potential along the NJ/DE coasts. There will be no large surprises.








A renewed hit of the polar vortex for the fifth time this season will bring deep winter cold back into the region for a substantial period of time. The further we go ahead the more relaxed this pattern becomes.












Cold air sticks around through at least the first 10 days of March.
















Long range model guidance has bounced around a large storm in the March 3-5 time frame. This could be our final significant snowfall threat to the big cities.











Winter Weather

Updated: 10:08 PM GMT on February 26, 2014

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Ice, Thunder, Snow, Cold, Coastal Threats

By: Pcroton, 11:37 AM GMT on February 20, 2014

2/23 3PM

Good Afternoon. Models beginning to find a consensus and that is of a weaker storm with a missed connection.




Updates begin on post #128



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2/23

One more day of warmth before we return to winter.

A light event will move through the region tonight with the heaviest potential focused over Maine. The chance of a more significant snowfall event exists for Tuesday night into Wednesday.

Updates begin on Post #112.


Tonight's maximum event potential:




=================================

2/22/2014

Good Morning. We still have a weak Sunday night system on the models and our Wednesday threat of which the models still are not within a proper window to generate an agreeable solution.

Update begins on Post #83


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Ice, Thunder, Snow, Cold, Coastal Threats


Good Morning. We have quite a rollercoaster ride on our hands here. A powerful low pressure area will be heading through the western Great Lakes into Canada will trail a strong cold front leading to strong and potentially severe thunderstorms Friday.

Due to cold air that is strongly locked in we have a freezing rain threat throughout the period across the northern portions of the North East and across southern Canada.





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HPC Hazards Maps:






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Ice Potential of a glaze or more through Friday Morning:





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Ice Potential of a tenth of an inch or more through Sunday Morning:




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There is even the chance of some accumulating snowfall between now and Saturday morning.
This is the HPC Maximum Reasonable Accumulation Potential through Sunday Morning. This is not a forecast.





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Temperatures will rise significantly on Friday aiding in a strong to severe thunderstorm threat.




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SPC Severe Storm Threats:




Thursday Threats:




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Winds will be a major issue with the passage of this low pressure area and cold front. I am concerned for areas of Pennsylvania and western New Jersey who experience the major ice storm not too long ago. Many trees that you believe survived the event are in fact heavily damaged and could be coming down in these wind gusts. An overly saturated ground from heavy rains couple with recent warming will increase the vulnerability of many trees.




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Flooding is of high concern given the wide ranging snow pack with a high water content. Heavy Rains are on the way. I think the HPC may be selling us a bit short here on QPF in the middle atlantic and north east.






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After this storm system pulls through for the fifth and hopefully last time this season the polar vortex will be influencing our weather. The same processes that have led to the continued return of cold air have remained in place. At least one week out of each month this winter we have seen mild temperatures only to return to three more weeks of well below normal temperatures and renewed snowfall threats.


The North Pacific SST Anomaly: This feature had rebuilt itself in recent weeks but has begun to wane yet not before contributing to the reloading of the winter pattern.





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The rebuilding western ridge and active sub-tropical jet stream:





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The polar vortex returns:






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The cold air plunges back in:





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Long range temperature anomaly outlooks:







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We also have several coastal threats that could become a reality. At this time frame all we worry about is the fact that the models continue to place disturbances in the region within a favorable pattern for development. Finer details won't be available until within a minimum of 72hrs of the onset of any event. Keep in mind the models will flip flop around on how to render this disturbance and it's energy as they try to time the interaction between polar and sub tropical energy. No model run should be taken seriously at this time. Here is the mid week disturbance:






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Threat #2:





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Winter Weather

Updated: 7:48 PM GMT on February 23, 2014

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Wednesday Ice Threat, Friday Thunderstorms

By: Pcroton, 12:08 PM GMT on February 16, 2014

Update 2/19 4PM

Afternoon Updates begin on Post #307

More freezing rain on the way for Thursday and Friday along with potentially strong thunderstorms Friday. After a few warm days we all cool back down beginning Sunday and there are a few coastal threats showing up on the models over the next two weeks.




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Update 2/19 7AM

Freezing Rain has begun in Pennsylvania and will head east through the morning hours. A strong to severe thunderstorm threat exists for Friday morning. Updates begin on Post #277









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Update 2/18 5PM

A freezing Rain threat has developed across Pennsylvania and points northward tomorrow morning.

Discussion begins on Post #249







Our Snow Storm continues in New England:



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Update 2/18 7AM

Morning Update post #187

Quick hitting system moving through the region this morning will wind up later this afternoon as it heads north east.




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Update 2/17 10PM

Evening Update Post #168

It appears the storm system is moving quicker and will push through the region during the early to mid morning hours. By the time temperatures become an issue in NJ the heavier precipitation may have passed.








Evening Update Post #168


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Blog Refresh, 2/17 4PM

Afternoon Updates begin on Post #70

The storm continues to develop and head eastward.






A light to moderate snowfall threat continues for the Middle Atlantic and North East with a more significant snowfall expected for northern CT, Massachusettes, SE New Hampshire, and Maine.





I believe the coastlines from New York City on southward are going to change to Rain on Tuesday while inland areas will remain as snow. This may keep snowfall totals down along the coasts.

GFS 10AM:




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Temperatures will warm after the event passes as we experience a week long break from the persistent cold weather. There is even a threat for strong to severe thunderstorms on Friday.








While we enjoy the warmer weather the pattern reloads in the Pacific and Canada and we will see yet another return to below normal temps and above normal precipitation. The same mechanisms that have led to this past winter are still in play and will come to bear one more time. More on that in the next blog entry...which will come out after this present system moves out of the area.

Winter Weather

Updated: 9:01 PM GMT on February 19, 2014

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Major nor'easter Pounding eastern New England

By: Pcroton, 4:30 AM GMT on February 10, 2014

Update 8PM 2/15

Major nor'easter still pounding Eastern New England.

UPDATES BEGIN post #1828








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Update 5AM 2/15


UPDATE BEGINS #1690

Significant Nor'Easter to affect the New England region - along with a moderate glancing blow for the upper middle atlantic states.






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Update 5PM 2/14

Evening Updates begin on post 1636.

SE New England to get hit hard yet again. Moderate snowfall accumulations expected in the upper middle atlantic stretching westward.

HPC Maximum Reasonable Snowfall Potential (not a forecast).



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Update 11AM 2/14

Seems with new 12Z Guidance that the storm threat is rising some for Friday into Saturday, particularly for SE New England.

12Z Model Updates being at post #1575
Previous storm snowfall reports post #1580



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Update 7AM 2/14

Updates Begin Post #1549

As one departs, Another looms. We have another system coming through later tonight into Saturday. While it appears to be forecasted as a light to moderate event a few well educated individuals were cautioning that models had been trending further north and it could end up a more significant event than thought. We will look into that as the day wears on.







New storm on the left in the center of the US.



974MB and dropping.



Reported totals thus far.



===============================================

Update 2PM 2/13

Afternoon update on Round 2, and a peek at Round 1 heading through New England begins on Post #1217.



Storm continues to wind up and pull away from the coast headed for New England.

A disturbance at 850MB is quickly intensifying over Virginia and will head towards NJ later this evening. Thunderstorms are firing within this area of disturbed weather.





A second potent burst of snow is likely late this evening through the upper Middle Atlantic. There is a threat of more significant accumulations in excess of 4" perhaps pushing 10" in the heavier bands and under convective cells with rates exceeding 2" per hour.


NAM Simulated Radar at 10PM:



Please refer to Post #1217 for more updates.
New WFO Snow Maps on Post #1224


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Update 5AM 2/13

Updates begin post #974.





Our storm is on track for a Cape Hatteras to Cape Cod course. Heavy snow has been falling but will transition over to a mix and then rain east of I95 as the morning progresses. Warm surface temps are along the coast and pushing inland. Aloft the freezing lines at 850 and 925mb have been lagging well behind so snow will be flying even as you go above freezing.

High winds along the coast as 50mph plus is already reported in Cape May. Dry air will be punching out the core of the storm this afternoon. A second round of snow comes later tonight with the development of a heavy deformation band.

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Update 5AM 2/12

All model runs are posted in Comment #1.
Morning Update begins on Comment #570

Good Morning. Dire situation unfolding in the south this morning. SPC thermal layers support massive icing event.

Further north guidance has shifted East (sans Euro) for the upper middle atlantic coast. I still believe in the colder and further east solution....HOWEVER..Miller A storms are very unpredictable in that they do take an "S" track first bending west up the coast and then back East. Also of note is the polar disturbance will be phasing with the surface low today. Until that happens it is still very difficult to pinpoint a track. A later phase means a further East track. As of this morning that appears to be what is going to occur - and just as much the surface low is further south in the Gulf than guidance had suggested. We will be watching this unfold today and then we will have a good feel on the storm later in the afternoon.

I want to say thanks to all who contribute and follow along.

I also think it's prudent to suggest if you have a storm idea it is not yet time to shift that idea (be it west or east). Stick with your idea until we see the storm evolve into a single organized entity.



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Update 6PM 2/11

Post #469 features latest WFO/HPC graphics.


While we have two model camps, one somewhat west and warmer, one somewhat east and colder, I continue to maintain my thoughts of the colder scenario playing out. At present the NWS has trended colder through New Jersey to the coastlines.

To be perfectly clear, while I believe in the colder scenario, it would be premature to put full confidence in that idea and discount the other model guidance and solutions. I think until the storm comes together tomorrow we don't really have a firm grasph on what track this storm will take. Even with a narrow guidance envelope any subtle change in the south can lead to a 20-30 mile difference up north very easily and thus dramatically shift the border zone forecasts, be it coastlines, or western edges of the precip shield.

To help us out in that department NOAA is launching Hurricane Hunter missions into the Gulf of Mexico tonight at 10PM and the Altantic Coastlines tomorrow. The data will feed into the models (not in time for 0Z tonight runs) and we will have much better guidance to follow for tomorrow's 12Z Runs.

One note about this: It shows just how serious this event is going to be and just how damaging the storm may be including high wind threats. They do not do this for your average gale. They only go for the big fish in winter. So it is an ominous sign they see something they haven't yet expressed to us and they feel the need to sample it.

==

000
NOUS42 KNHC 101620
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1120 AM EST MON 10 FEBRUARY 2014
SUBJECT: WINTER STORM PLAN OF THE DAY (WSPOD)
VALID 11/1100Z TO 12/1100Z FEBRUARY 2014
WSPOD NUMBER.....13-073

I. ATLANTIC REQUIREMENTS
1. FLIGHT 0NE -- TEAL 71--
A. A66/ DROP 9(28.2N 93.8W)/ 12/0000Z
B. AFXXX 05WSA TRACK66
C. 11/2000Z
D. 10 DROPS ON TRACK AS PUBLISHED
E. AS HIGH AS POSSIBLE/ 12/0200Z

2. OUTLOOK FOR SUCCEEDING DAY:
A. A62/ DROP 7(34.0N 72.3W)/ 13/0000Z

===========================

Update 5AM 2/11

Good Morning. Our storm continues to develop and our disturbances have entered a denser sounding network. This means we will have much better data starting with today's 12Z Model runs.




We are looking at a severe icing event for the SE states and some of the totals make my stomach turn.

Further north we are dealing with heavy snows and the questions of changeovers, when, where, how much...are still left unanswered at this time.


Post #227 begins Today's updates.

Post #1 has a list of archived model runs.

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Update 4PM 2/10

Guidance continues to point towards a high impact wide reaching nor'easter.

The storm's main components are all coming together nicely.



All relevant model runs are in post #1 in the comments section.

Morning updates began on post #13



Evening updates being on post #136

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Update 8AM, 2/10.

Threat for severe nor'easter has grown. A storm featuring very heavy wet snow, heavy sleet, and heavy freezing rain along with high winds and coastal flooding is a good possibility.

Please refer to Post #1 in the blog for latest model runs.

This mornings updates begin on Post #13

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2/9 - 1130PM

The threat of a major winter storm bearing down on the region from late Wednesday through Thursday has risen significantly.

Future model runs and maps will be posted within the comments section as the system evolves. Refer to the latest comments for the most up to date information.

Remember, the models do not drive the weather, and our emotions do not decide which model run is the correct one. They are a tool, not a forecast, yet with them in decent agreement here they are tough to ignore now that we are within the 72 hour window.

At this point don't focus too much on exact track or intensity. The models will begin to tighten up once we enter the 48 hour window. Fine tuning of rain/snow lines in sensitive areas are best left to 24 hours and in. Monday will be a big day to answer questions on just how big of an impact this system will bring to the region. There is still a wide range of final solutions in play. I think our best bet to start getting confident will be some time late on Monday.

If you wish to read up on Sunday's discussion and get caught up on why Sunday's system did not turn into the major winter storm we once thought it would and how that plays into looking forward to this coming event please read Sunday's short blog entry.


Here are your model runs (all in comment #1), three suites where applicable, both 00Z and 12Z runs from 2/9 and the 00Z 2/10 runs. I felt it was important to include all 3 runs just to give everyone a look into how things have evolved. I was hoping to have the full suite of 2/10 00Z runs included but these things take time to become available and we can address them in the morning.

Remember, we're not quite there yet, but the NWS has raised some early warnings in the form of area HWO's calling for 6" or more of snow. The threat is real but is not confirmed at this time. This all comes down to timing the phasing of the polar and southern stream energy. We won't have a good handle on that for at least another 24 hours.

Keep checking in for updates as new information becomes available.

Winter Weather

Updated: 12:41 AM GMT on February 16, 2014

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Prolonged Winter Threat this week for the East Coast.

By: Pcroton, 1:02 PM GMT on February 09, 2014

Good Morning. Today's system continues to disappoint but I'd never say no to snow even if it's just an inch or two.

The images below illustrate why this happened and what the distance was between a huge storm and this strung out energy.

So why no big storm today? That's easy to see now.

In the long range the models expected the two circled disturbances to interact and phase. Had they done so we would have had a big storm hit the region. That's it...nothing fancy. 7 days out they saw these two disturbances lined up. 3 days ago they no longer saw it. That's why we are where we are. Had these two aligned (missed by 24 hours) you get a big winter storm.











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For today's weather:

















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Longer term has become more complicated than ever. While it is too early to begin to have faith in model guidance the topic is on everyone's mind so I decided to cover it.

This is not just a case of one low pressure forming in the south and coming up the coast to phase with a polar disturbance. There are now signs of a multi-headed event and as we know up north that can really cause problems for the "big one' to develop due to all the shared energy and strange steering patterns that result.

It looks like several waves of low pressure effect the south and they greatly affect how the final storm system is going to wind up. The NAM illustrates this best except that with the run ending at 84 hours it just starts to show the final disturbance forming out over the Gulf back towards Mexico. The GFS and CMC went wide right again while the Euro is steadfast in bringing a very strong low pressure area up the coast.
















All systems appear to phase but at different times and locations. The flow is progressive with the NAM/GFS/CMC which explains the wide right tracks in their runs. NAM upper air not included as it is too early in the final storm development.











It looks as if one of the problems is a third polar disturbance riding the northern stream. Unsure if this is something that could phase as a third disturbance leading to a major storm or if it's just a disturbance that is riding through the flow and since it must come into the area it forces our storm to depart wide right and quickly. If this disturbance did not exist perhaps the flow isn't as fast and the storm would ride the coast as the Euro shows. Same goes for if it was a player to be a secondary phasing adding energy to the storm system and pulling it up the coast. These little details are an impossibility at this range.








I still caution we're way too far away and now with such a tricky setup unfolding with multiple disturbances that shortens the window of guidance trust even more as with Tuesday's systems in the way the models just will not handle the Wed-Thu system well at all. Very complicated!

Here is how the HPC handles the onset of all of this. This is good through 12Z Wednesday (Wednesday 7am)







Here are the much maligned snow maps covering the southern swath of snow. These are not forecasts. They are model outputs. If the model is handling the storm incorrectly then these maps will be incorrect. Yesterday's 12Z NAM bombed the swath with 12" and more while the GFS was 8" and more. Now here's the 0Z runs. No telling at this stage which model run is correct. However this is good to at least illustrate where the snow threat is at this time. As far as northern reaches for the final bigger storm? Too far in advance to even bother there.









A new blog entry will be out when we start to see guidance tighten up and a solution come forward.

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Snowmageddon or Snow Showers?

By: Pcroton, 1:14 PM GMT on February 06, 2014

As we've seen all winter long the models will pick up on and maintain a specific disturbance for several days in the long range, the media, the NWS, and us hobbyists will talk and discuss and post model runs and maps thinking storm.

Then we reach the medium range of 48-120hrs and the models start to waver, some losing the storm, some sending it far north, others far south, and some times splitting the energy preventing a signifcant event from unfolding. Most who were talking up a storm begin dropping the storm idea as a result.

Short term arrives and the models start to latch back onto an event, showing a more organized solution back in the region, and forecasters and hobbyists alike begin to revert their thinking back to a storm solution.

We saw this occur yesterday with the NWS backing entirely off a storm solution in the morning and then opening the door back up to the idea in the afternoon and evening.

This upcoming period of disturbances, 3 over the next 10 days, will be no different. They will come and go on the models in various forms and we will discuss them and waver along back and forth with the guidance until we see something we like and we will throw out our ideas with confidence with or without model support.

While thoughts of Snowmageddon have certainly waned for this weekend there will be a disturbance driving through the region around Sunday and the NWS is now supportive of this idea in zone forecast products after back tracking last night to open the door back up a little for the idea of a storm system.

Modeling has come back a little as well but it appears Sunday will be a light to moderate event as energy is shown as disorganized on the model runs with a piece just off shore and a piece just inland not quite being able to hook up for a more significant event. Being 72 hours out I am still a little uncomfortable trusting model guidance as I have noticed we have been generally held to 48 hours and in as far as confidence goes all winter long. We've seen these systems modeled weakly 72 hours out and the 36 hours out they start to look a whole lot better.

Just yesterday we had more well defined systems but well outside the region...but this morning less defined yet going right through the region. This I feel means the models are still not geting the necessary data to spit out a viable solution. We should see this improve with the 12Z runs today, more in tonights 0Z runs, but I think Friday's 12Z runs are where it's at in terms of "Ok, now we have a model solution we can trust and discuss and forecast from."

The GFS for Wednesday which I believe might be more interesting than we are being led on to definitely paints the picture of a large storm. We've seen these modeled south recently only to creep northward over time and end up as a major player. Stay tuned


Here is the CPC 6-10 day precip and temperature maps as of 2/6. Cold air and moisture spell high chances of stormy weather.







Model runs to follow in the comments section.

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Wednesday SEVERE Ice/Sleet/Snow MidAtl to NE

By: Pcroton, 11:04 AM GMT on February 04, 2014

Good Morning.



Advisories as of 6AM Tuesday

Looks like we have a dangerous winter weather event on our hands for Wednesday for the region.

Let's start by looking at what the models are doing. We appear to have an inland low that will transfer it's energy to the coastline. As we know the earlier this occurs the colder the solution.






Now let's choose a model run. Monday's snow pack was important and it's best to see what model is handling the new thermal environment the best.

So let's take a look back at yesterday's 12Z Low Temperatures for this morning from the NAM:





And now the GFS:




And let's look at the present surface Analysis:




Blue=32F Line. Isotherms are 2F scale.


I'm sold on the GFS here. It is handling the thermal environment properly. Yes, that same GFS that was a disaster for yesterday's storm and that same GFS that once had today's storm in the western Ohio Valley heading into Canada, which those who follow my blog, knew I was steadfastly against that and the forecasted warm rain scenarios that were born of it.


==================================

Now let's take a look at how the models are behaving. With a colder environment I expect a further East storm track which would lead to an earlier transfer of energy towards the coastline.

Our Canadian model nailed Monday's storm so let's take a look at that first.

CAN 30HR:




CAN 39HR:




Notice how the parent low is far inland and maintaining intensity. This is in error as the low must transfer to the coast. I would discount this model. It als seems to be too warm in regards to our sleet and freezing rain threats.

Let's check the NAM out:





Like the Canadian model the NAM also hangs on to the parent low too long. I don't hate this model run but it's just too late with the energy transfer.


Now let's check the GFS.






The GFS has the evolution of the storm and it's transfer to the coast properly here. I would go GFS with track.

The GFS is too warm here too early however we know the GFS tends to have a warm bias as it has all winter long so I like the track but I think you can knock a good 2-4 degrees off of this map you see here and that spells trouble. While the GFS had the initial environment correct it is kicking out the cold air far too early. With such a good snow pack in place combined with very cold overnight temperatures that cold air will take hours longer to evict than the GFS is showing. This is why you lean low here.


Let's take a look at the upper levels this morning.

850MB LEVEL




925MB LEVEL




Notice how the 850MB level is warmer than the 925MB level and surface. This screams sleet and freezing rain. The 850MB level will feature liquid which will fall through the 925MB level and refreeze and hit us with sleet. In areas where both levels are above freezing the liquid will reach the ground and flash freeze on surfaces.

Prior to this we will have snowfall and areas north of Interstate 80 will have a long duration snowfall event before some sleet creeps in halting accumulations. Don't use these maps to illustrate rain/snow lines. Where you see lower snow totals there's going to be sleet not rain. Just as dangerous if not more so. Too much emphasis
is always put on accumulation totals and not actual threat.







The GFS has this correct. I am unsure, given the cold temperature profiles, why the GFS snowfall output is colder while the NAM is warmer. Quirk in the system? Those snow maps are no stranger to fault.


Now given the upper level environment which we will have to NOWCast early in the event, I would discount colder surface temps as a reason to expect more snow south. If we get more snow south it will be about that 850MB level dragging it's heels in the south....and not about our surface temps staying cold. Surface temps staying cold will prolong our sleet and ice event.

All about the 850mb level if you want to stay SNOW in this one. So watch that evolve and see how it marches northward. Sleet is all about the 925 staying cold.

I dislike the GFS's handling of temperatures during the storm however here is it's 850MB levels at 30hrs and then 36hrs.






Now here is the colder NAM, whose temperatures I like except their exact contours are iffy due to the primary low still holding on too long in it's solution. Since the GFS is too warm this will suffice for a theory on our storm outcome.

850MB at 30hrs:




NAM at 42hrs:




Here is the NAM at 30 and 42 hours. Notice where it sets up the 925MB (sleet) level and doesn't budge it. North of this freezing (white) line you do not go over to rain. You are sleet and north of the 850mb freezing line you're snow.







I would go GFS track/evolution, NAM temps, GFS Snow Map.


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Lastly, your HPC products.

Freezing Rain > 0.10"




Freezing Rain > 0.50" (damage)




Snowfall > 2"





Snowfall max worst case (I would go with it.)





I will address finer point details and more maps/model runs in the section below. I will answer some late questions from the last blog and also touch on yesterday's failures in the south.

As always thank's for participating. This is an open blog. We don't keep score here. We analyze and discuss what storms may or may not do. All thoughts are welcome.

Updated: 11:33 AM GMT on February 04, 2014

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About Pcroton

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