The model depiction of the small low pressure system expected to affect us on Thursday night into Friday continues to evolve.  The NAM and GFS differ on timing and coastal development.  The GFS has a more substantial coastal storm developing on Friday and coming very close to PHL, but the heasiest precipitation shield still misses us.

It should be noted that the degree of coastal development and the degree of upper air troughing continues to change, with the trends leaning to the possibility of more snow than the currently expected 1 to 2 inches.

Put another way, it wouldn’t take much change for the snow in our area to be more significant.  It also wouldn’t take much change for it to be just a period of snow showers.

To give perspective on the model’s continuity, tonight’s rainfall, originally expected to be quite heavy, doesn’t appear that it will be be very significant.  So confidence in the forecast for Friday continues to be lower than usual.

11 pm –tonight’s GFS has increased the QPF to 0.33 inches water. The NAM has reduced it to 0.07.  Large model differences!

The models have been showing a fast moving low pressure system moving to our south Thursday evening and redeveloping off the coast as it moves eastward Friday morning.  Snow would start Thursday evening  and end early Friday morning

Accumulations appear to be light at the current time from this system, but the trend has been for increasing amounts.  There is still uncertainty regarding this potential snowfall.  Stay tuned.

Tues AM: Last night’s models has a QPF of 0.14 inches water for Thursday evening into daybreak Friday morning.   That’s about 1-2 inches of snow accumulation by Friday morning.

Had this amount of QPF fallen during daylight hours, there would be even less accumulation due to solar insolation from the March sun, but because it is falling at night at the lowest diurnal temperature range, the 1, maybe 2 inches is a possibility,

The GFS continues with snow showers during the daytime Friday, but little additional accumulation from these is expected.

There is still uncertainty about the specifics with this low pressure system, which should become clarified over the next several days.  (To give a sense of the uncertainty, tonight’s expected rainfall was supposed to be heavy, but the latest models have little QPF.)