More winter weather on the way as Freehold digs out of another blizzard

The entire northern Mid Atlantic is digging out of 6 to 24 inches of snow that feel over much of the region the past 24 hours as the blizzard that impacted the region exits into the Atlantic.

The water vapor satellite image this morning clearly shows the exiting intense area of low pressure moving into the northern Atlantic.  This storm will continue to have an indirect influence on the upper level pattern over much of the Northeast and Mid Atlantic for several days.

Meanwhile, the Sub Tropical jet stream will remain very active with plenty of moisture and weak disturbances moving through Southeast with some wintery threat for locations to the south of the Mid Atlantic through this weekend.  However, for the New York City and Philadelphia metropolitan area, the weather conditions will become a bit more tranquil at least through the weekend.
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Another significant snowfall on the way for Freehold

Here we go again!  Another major winter storm has a target for the northern Mid Atlantic with the potential for another one to two feet of snow for many locations in the New York City and Philadelphia metropolitan area along with very strong winds and near zero visibility for Wednesday morning.

The water vapor satellite image this morning displays all the players for this major winter storm.  The first feature to take note of is the strong upper low, enhanced by the last major low pressure system, over the Canadian Maritimes.  That is the 50N/50W upper low that is key for any significant winter storm.  This upper low is in a near text book position to support a major to potentially historic winter storm for the region.  The position of this feature on all guidance strongly supports a stormy track from North Carolina to the bench mark.  
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Uncertainty remains as major winter storm heads east

I would love to say this morning that I know exactly what this storm is going to do and that I have complete confidence in the way the models are handling the moisture advection at the mid levels, the expansion of the precipitation shield, and the strength of the Sub Tropical disturbance.  If I could say that, then this forecast would be very easy.  Of course, I can't say that and this morning, while issuing the first snowfall map, I am also going to address my concerns with this storm.

To the left is the snowfall forecast I am currently going with based on all the guidance I have available and some tweaking via observations of the radar and satellite images.  My original forecast for a moderate snowfall event for northeastern Pennsylvania through the New York City metropolitan area remains with generally 3 to 6 inches for New York City and 2 to 4 inches to the north over Connecticut and the Hudson Valley.  The heavier precipitation and best lifting will be focused to the south as this storm is expected to really nail Washington D.C. and Baltimore with potentially over 20 inches of snow.  The Philadelphia metropolitan area will come in to 6 to 12 inches of snowfall with higher amounts over southern and southeastern New Jersey of 10 to 15 inches of snow.  Cape May, New Jersey is looking like the prime area to be for regional snow lovers as up to 20 inches of snow will be possible.  Go figure!  Who would have thought Cape May, New Jersey would end up with more snow this season than Allentown, Pennsylvania?
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Significant Winter Storm Begins To Take Shape

As one low pressure system exits from the region, another more significant storm is already organizing over the Southwest and northern Mexico.

The low pressure system that is exiting into the Atlantic this morning produced a light snowfall with most locations receiving 1 to 3 inches of wet snow.  The low pressure system will continue to move east and intensify over the northern Atlantic as skies clear over the Philadelphia and New York City metropolitan areas.  High pressure will take hold today through Friday morning with few to scattered clouds and temperatures averaging near normal in the mid 30's for most locations and slightly colder over interior and valley locations in the upper 20's to lower 30's through the period.

All eyes are naturally focused on the potentially significant winter storm for much of the northern Mid Atlantic.  Before going into detail about the threat map I have posted below, I want to touch on some concerns I have with the model guidance up to this point.
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Scattered snow showers this afternoon appetizer for this weekend

A weak low pressure system is approaching from the Ohio Valley this morning that will interact with a Sub Tropical disturbance this evening along the Mid Atlantic coast.  This low pressure system will redevelop east of Delaware, producing scattered snow showers throughout the New York City and Philadelphia metropolitan areas this afternoon through tonight.

The progressive nature of the pattern over the next 24 hours will prevent this low pressure system from slowing down and deepening off the New Jersey coast, but instead intensify well into the north Atlantic.  As a result, no significant accumulation from the snow showers are expected.  However, a few snow showers will be able to produce a quick burst of snowfall this evening through tomorrow morning, which may have an impact on travel conditions for the rush hour periods.  Otherwise, no appreciable accumulations are expected as this low pressure system exits to the east.
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Arctic cold start to the day, snow on the way!

There's a lot to cover this morning!  So let's get to it!

The area of precipitation that will impact the northern Atlantic this afternoon through this evening is currently developing over the Tennessee Valley and western Virginia under the influence of the strong Sub Tropical disturbance that is driving towards the Mid Atlantic coast.  The surface low meanwhile is driving into southwestern Georgia and will move towards the North Carolina coast by this evening.
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Snow still a threat for this weekend

I would love to be able to say I know exactly what is going to transpire over the next five days and I am extremely confident in the forecast I am going to issue.  The problem is that I can't say that and likely won't be able to say that until Thursday night.  Over the past 48 hours, I've been following the track of a strong Sub Tropical disturbance moving into southern California and a strong Polar disturbance and eventual Polar Vortex diving into Ontario.  The combination of these two features have the potential to produce a significant snowfall or a complete miss depending on how each feature interacts with each other.  Naturally, the model guidance the past few days have produced a variety of solutions from a significant heavy snowfall for all of the northern Mid Atlantic to a complete miss with no snowfall on yesterday's 12Z guidance.  The latest 00Z guidance has trended a bit further north, and the Philadelphia office of the National Weather Service noted the same error that I noticed this morning:

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The water vapor satellite image this morning now has the Sub Tropical disturbance and Polar disturbance beginning to enter the United States.  Note the strength of the Sub Tropical disturbance which is driving moisture northward over the Southwestern United States and appears to be very well developed.  Also note that the Polar jet stream has established a well developed trough stretching from the Rockies towards the Mid Atlantic.  The observations above are important because of the potential implications on how model guidance overall is handling the development of the Polar Vortex and therefore the idea of suppressing the stormover the southern Mid Atlantic.

The most damning argument against the suppression idea of at least the mid level moisture is trends of the indices and the forecast of those indices over the next five days.  When I look for a pattern that features suppression, I usually look for a rapidly falling North Atlantic Oscillation, sometimes coupled with afalling Arctic Oscillation.  What this basically illustrates is whether a strong upper low will be present either over Ontario, Quebec, or the Canadian Maritime.

However, instead I see an argument to allow the Sub Tropical disturbance to "turn the corner" and have a more substantial impact on the northern Mid Atlantic.  The NAO iscurrently slightly negative to almost neutral, with a forecast for a slight dip in the index in the next 5 days, but nothing to argue for a strong suppression.  Meanwhile, the AO is in a period of rapidly rising, likely meeting an apex of the positive trend in the next 2 days followed by another decline.  The point however is the AO will actually end up slightly more positive the next few days than current observations.  Again, this is an argument against suppression.  I also took a look at the PNA observations and ensemble guidance.  A weak positive PNA environment is in place with more neutral conditions expected the next 5 days.  The overall average of guidance does produce a ridge axis over Montana, which does argue for a stronger Sub Tropical disturbance than currently forecasted as the magnitude of the trough should be sharper, this correction was starting to unfold in the 00Z guidance.

However, there are other considerations to discuss with the forecast, namely the impact of dry air.  After seeing other storms from the past fall through this current winter being impacted by the influence of dry air, you can bet I am taking that into consideration.  The air mass in place by Friday morning is a true Arctic air mass with very low dew points, like below the mid 10's for many locations, to be in place.  The impact of this dry air will be an agent to "suppress" low level moisture from reaching many locations over the northern interior in my opinion even if the storm does end up further north.  So while plenty of mid level moisture may be able to push north on Saturday morning into the Hudson Valley, the result may be a long period of frustrating virga while many snow lovers look at a radar that says it's snowing when it is not.

At this time, I am not confident enough to issue even preliminary snowfall accumulations.  However, I am issuing a second threat map to cover the thoughts above.  Given the data above, I think there is potential for this storm to end up further north with a significant amount of moisture impacting at least the Philadelphia metropolitan area and possibly the New York City metropolitan area on Friday night through Sunday morning.  At this time, I think the air mass will be too dry for locations like northeastern Pennsylvania, extreme northern New Jersey, the Hudson Valley, and interior Connecticut to get an accumulating snowfall.  The strength of the Arctic air mass is not going to be under forecasted by this forecaster this time and I think the magnitude of dry air in place will limit the push of snowfall to the north.  However, on the other side of the coin, those in southern New Jersey, especially southeast of Philadelphia better not let their guard down.  A slight shift of this storm to the north would lead to a moderate to heavy snowfall with temperatures in the 20's at the surface and around -8°C at 850 MB, leading to a high liquid to snow ratio.

The point here is that the best course of action is to take a wait and see approach on just how strong the Polar Vortex and Sub Tropical disturbances really are.  If the actual observations and trends continue, I think that much of the Philadelphia metropolitan area along with central and southern New Jersey still stand at having an accumulating snowfall Friday night through Sunday.  However, locations north and west of Philadelphia and New York City are likely not to be impacted by this storm given the upper level pattern and the strength of the dry air I'm expecting with the Arctic air mass.

After this storm exits, high pressure will take hold Sunday afternoon through Tuesday with scattered clouds, dry conditions and temperatures running near to slightly below normal.

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Return to cold conditions as snow threat increases for this weekend

A weak disturbance behind the exiting cold front from yesterday, which produced rainfall amounts well over an inch in many locations, flash flooding, and some wind damage, has produced a few rain and snow showers early this morning, but is exiting into the Atlantic.  A deep Polar trough is become established over the eastern United States with a variety of weak disturbances rotating through the Mid Atlantic.  However, surface high pressure will be the primary influence today through Thursday morning with generally dry conditions and temperatures returning to near normal levels for this time of year.

All eyes are drawn to the end of the week and this weekend where the potential for significant accumulating snowfall returns to the region.
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Heavy rain impacting morning rush hour, threat for significant snowfall growing for this weekend

This morning, an impressive cold front is moving through central Pennsylvania and producing heavy rainfall throughout the Philadelphia and New York City metropolitan areas.  The cold front will continue to progress east this morning and exit the New Jersey coast by 12 PM and eastern Long Island by 2 PM.

The rainfall with this cold front will be heavy at times, leading to flash flooding of streams, small rivers, and urban locations at times.  Temperatures ahead of this cold front are very warm with most locations in the lower to mid 50's and Philadelphia in the upper 50's pushing close to 60 degrees this morning!  However, as the cold front exits, strong cold air advection will force temperatures to fall through the 50's, 40's, and eventually the 30's by late this evening with a gusty northwesterly wind.
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Major winter storm to impact Monmouth County

As I woke up this morning to look at the 06Z guidance, I had to laugh to myself.  Models converging on an idea for this storm?  Yeah right!  Of course, who thought this was going to be easy.

This morning I went to a tried and true method that I learned back in college and it is called learning from the past.  This storm is roughly 24 hours away from impacting the northern Mid Atlantic one way or another.  Based on previous storms over the past 50 years, the 500 MB pattern in place this morning strongly supports a heavy snowfall over the New York City and Philadelphia metropolitan areas.

As for the model guidance, if I was to pick a combo that is best dealing with the current develops and what will follow in the next 3 days, I would go with a combination of the UKMET and the ECMWF guidance with some tweaking on the QPF to deal with mesoscale issues, which I'll cover in a moment.  These models have been the most consistent for the most part in the overall idea of this storm.
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