As I’ve mentioned,  over the past two weeks, the GFS model has been showing the return of cold air and the possibility of snow for this coming weekend.

The models continue to show this possibility.  The GFS model QPF for late Saturday night into Sunday is well over 0.40 inches water equivalent, but the exact track and timing of the coastal low’s intensification is still uncertain and continues to be difficult to pin down.  What does seem likely is that the upper air thermal profile supports snow, vs rain.

Even if the expected QPF value gets consistent, predicting snowfall amounts this time of year is very difficult.  So much will depend upon the timing (daytime vs nighttime) ground temperatures (which are high for this time of year),  near surface air temperatures and rate of precipitation (which affects dynamic cooling.)

So this is NOT a snowfall where you multiply the QPF by 10 and you get the snowfall totals.  Instead, all of those factors above turn into a general crapshoot predicting accumulation.   To simplify, snowfall during the daytime hours reduces accumulation significantly, especially on dark paved surfaces.   Grassy surface accumulation almost always exceeds accumulations on sidewalks, unless precipitation rates and QPF amounts are very high.  Right now, it doesn’t look like a ‘big event’.

Both the NAM and GFS models have light snow starting Saturday evening and continuing into at least Sunday morning, maybe more prolonged. Temperatures will be cold and below average late Saturday through Tuesday.

Thurs 11PM – NAM QPF looking impressive at 0.56 inches water equivalent.  Accumulating snow looking more likely during the day Sunday.