Midweek Nor'easter to Impact Region

There will be a strong nor'easter developing along the east coast this week.  While the intensity of this nor'easter (May receive a name from the Weather Channel; would be Athena) will pale in comparison to Sandy, it will cause further problems for the areas hardest hit by the storm.  For coastal areas additional flooding is likely and for areas well away from the center a healthy dumping of snow will occur.  There is high agreement among model guidance on this event which is remarkable for this range.  When there is a block in the Atlantic computer guidance skill increases according to Dr. Ryan Maue of Weatherbell.

I'll show the evolution of this system and add some analysis on the weather preceding the Nor'Easter.  Please remember that in the atmosphere pressure decreases with height.  900 mb is around 5000 feet, 500 mb is around 18,000 feet and 300 mb is around 30,000 feet.

Surface Analysis valid Monday 230 AM

A strong low pressure system is about to impact the Pacific Northwest.  High pressure in control over Central Canada sending a cold Arctic air-mass into the Eastern Half of the United States.  Several low pressure systems are diving across the upper plains and a boundary exists along the gulf coast.  At upper levels the set up looks like this

500 mb
05/06 NAM run, initial conditions 
Polar vortex is over Canada allowing overnight lows to drop into the 20's for much of New England.  Energy diving through the Great Plains and more about to effect the Northwest.

300 mb
300 mb Jet, also 05/06 NAM (1 am this morning)
Strong Jet in the Pacific while the southern stream is over the Gulf Coast.

Now tonight, 7 PM
850 mb wind and Surface Pressure.  Image from Dr. Ryan Maue and Weatherbell EURO model
Tuesday will be nice across the northeast, albeit chilly.  Highs will only reach the low 40's in Southern New England.

500 mb
A well defined shortwave cutting through Arkansas
You can see the wave over Arkansas on both the surface and 500 mb chart.  This is the upper level support for the surface feature.
300 mb
Near record warmth likely out west with ridge, favors deepening trough over East
A classic Nor'Easter set up with a ridge out west, trough east, and subtropical jet stream running along Gulf Coast.

Now Tuesday night 7 PM
Low pressure to from along Gulf Coast, cross Florida and begin to strengthen over Gulf Stream
Again this is the EURO model which is the best of the medium range guidance.  Storm is taking shape off shore.  Blocking still dominating in the Atlantic so nowhere for this storm to go but up the coast.

500 mb
Upper level energy maximum right along the coast, favors a low pressure center just offshore
Ridge is really pumping out west allowing for the eastern trough to capture the developing nor'easter.

300 mb
Add caption
Energetic Jet to interact with storm while it makes its way up the coast.  This will allow the storm to deepen rapidly.  

That is how the upper air will allow this system to develop.  The end result for Wednesday night is this
EURO 72 hour forecast
The end result of all these images is a long duration slow moving Nor'easter will impact Southern New England and the Mid Atlantic.  Snow will occur on the far back side of the system.  The American GFS is showing this for snow totals
GFS valid Friday morning 7 am
This is probably a bit over done as I expect a track more over the outer cape, but if it is just over the benchmark (40 N. 70 W) somebody can look for close to 10 inches of snow especially in higher terrain.  For rainfall I defer to the HPC.  Here is their 5 day totals
5 day rainfall outlook
Thats a general 1-2 for most, isolated 3-4 inch amounts.  These heavier bands will be able to mix stronger winds to the surface.  Isolated tree damage and power outages are possible especially along the coast and Southeast MA, RI, CT, and Long Island.  Of course this is no Sandy but its still a strong storm and needs to be taken seriously.  I will post again tonight or tomorrow and will be more brief, just wanted to show the evolution of a Nor'Easter.



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