Mike Masco: A split in the models to become a HUGE forecast challenge ahead.

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Here we are.. Friday at 1pm and still a few uncertainties in respect to the weekend storm threat Sunday AM - Sunday Night.

WHAT WE KNOW..

1.  This is not a phased system which will enable a storm track to climatologically favor the Mid Atlantic to see the most snow

2.  A nighttime event looks likely for Baltimore and Philadelphia which support accumulating snows

3.  The highest elevations over the Appalachian mountains will see the best snows with longer snow duration from Sunday early afternoon to Sunday Evening.

WHAT WE DO NOT KNOW..

1.  The Storms exact intensity and moisture field by Sunday afternoon 

2.  Exact track of the surface low as it interacts with the northern stream and 50/50 low setup.

THE MODELS..

We can officially rule out a full phased system from the equation as we progress into the weekend.  The model support is locked in that the northern vort max (shortwave) will get caught up in a very progressive northern jet stream and will consolidate with the quasi 50-50 low over SE Canada.  In this situation we deal with a low that will run out of the southern jet stream and try to move north as it intensifies and tries to turn the southern jet negativity tilted.  

500 MB MAP GFS 12z 

 We then focus on our cold air source.  There looks to be a 1025 MB HIGH (via the NAM) and 1023 MB HIGH (via the GFS) over central New England.  This will be key to keeping a wind direction NW or N during the duration of this event.  Intensity of this High will be critical to this event and how much snow will fall.  The 850 MB temps support snow however the 2M temps over the Delmarva and SNJ are borderline at best.

NOTE the HEIGHTS building over the storm.  This will ensure all snow from western MD into West Virgina and NW Virginia 

 The Track of the storm is interesting.  The RH field moistens the atmosphere up to NYC on the NAM while it suppresses it to SNJ on the GFS (With the European model siding with the GFS)

The European Ensembles are still pretty broad however the consensus brings the low from Nags Head to Cape Charles. 

Operations EURO INLINE with the GFS

MY THOUGHTS.

I feel we have a storm that will inch itself north during the course of Sunday.  A stronger storm will tilt the jet more negative which will bring more moisture north while A weaker storm will keep it south.  Evidence of that shows up between the NAM (997MB storm) while GFS (1000MB) once it moves off the coast.  

This is the WV imagery right now.  The southern cutoff is very strong but whats impressive is the amount of moisture ahead of the system that is advecting North as we speak. 

IR imagery shows this nicely.  The amount of moisture to be tapped into is not being played out as well as the GFS shows it.  

2ND CALL MAP OUT AT 5PM THIS EVENING !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!