After The Warmth, A Mixed Event?

After the near record (or record tying) warmth on Friday, reality returns at some point on Saturday as a cold front slides on down from Canada and puts an end to our spring fling. Saturday will probably feature a "midnight high" as colder air pushes in during Saturday on northwest winds. Saturday won't be brutally cold but reality will slowly set in as temperatures don't move much during the day and colder winds bring reality on back for Sunday into Monday.

With that February reality comes the chance of some precipitation on Monday or Tuesday.  Depending on your choice of computer guidance, you can have any one of a litany of precipitation types.  The colder Euro (below) is suggesting an overrunning snow event in the city, with ice and rain to the south of the city for Monday night and Tuesday.   A decent event -- a few to several inches of snow -- would accumulate from this scenario IF the Euro were correct.  The Euro shows low pressure weakening in Western Pennsylvania, transferring its energy to a surface reflection off of the Virginia/North Carolina border.

The GFS is stronger with the low and as a result tracks it farther to the north as it gets pulled north of the region initially.  Since the low is north of us, we see a bit of ice (mainly north) transition to overrunning showers before temperatures bump higher Monday night (50's?) ahead of the front.   The GFS is also a faster moving system, with the majority of precipitation in Philadelphia on Monday and only some frontal band showers early on Tuesday morning with the cold front.

There are a couple of major points on the computer models besides the differences strength and timing.  One, the storm system will have a genesis in the Plains and will lift northeast into Illinois.  At that point, the models diverge a fair bit...with the GFS taking the low generally east through Michigan and then into New York State as it rides east around the Southeast Ridge of high pressure aloft.  

The Euro has a weaker depiction of this ridge in the atmosphere.  This is critical because as the low works east, it runs into high pressure in Canada trying to nose down.  As this high in Canada noses down it begins to suppress the low pressure and the the flow between the highs to the south and north shear the system apart, weakening it and sending the system east-southeast. The Canadian high filters in additional cold to the surface, allowing there to be a snow/ice scenario.

Between these two benchmarks reality is probably going to be the resulting storm track, which means a mixed bag event for the region.  Odds would favor colder north, milder south, which means the battleground is in between.  The question is which side "wins" more -- the warmer GFS, which would bring rain to most with maybe some ice on the front end or the colder Euro.   One of the other sets of guidance to look at, the Global (Canadian/GGEM), is suggesting a mixed bag event that ends as rain after an early shot of frozen precipitation on the front end.

Until the weekend...or more consensus is reached...enjoy the upcoming warmth!