Saturday, March 23, 2013

Forecast for Sunday, March 24, 2013


There is a pretty decent spread between the NAM and GFS MOS guidance maximum temperature values during the next 48 hours. I sided with the GFS temperatures for Sunday which are warmer than the NAM temperatures considering I expect partly sunny skies through late in the afternoon which should result in some surface heating from the high sun angle.  I sided with the cooler NAM temperatures for Monday considering that I expect Monday to be cloudy with precipitation.

Clouds will increase on Sunday Night. Some precipitation may develop late on Sunday Night with a mixture of wet snow, sleet, and rain. At times, it may switch to all wet snow until the sun rises on Monday and works its magic causing the wet snow to mix again with the exception being in the colder, higher elevations. South and East of the city, this precipitation may switch to plain rain for much of the daytime hours on Monday. Perhaps even in the city metro itself. North and West of Philadelphia is where there will likely be some form of mixing with little or no snow accumulation. In the Poconos, it should be cold enough to support mainly snow with some accumulation possible.

Given our sun angle is post-equinox, solar strength is pretty strong, and given the bottom portions of the atmospheric profile will not be terribly cold with most areas having surface temperatures above 32 degrees, you would need heavy precipitation to get snow through the atmosphere and for it to stick.  There will be precipitation, but it may not be heavy enough to drag enough cold air down to make the snowflakes and sleet pellets survive into the surface layer and cause conditions that would support the snow sticking. However, March storms can bring surprises and there could be some locations of enhanced banding resulting in a wet snow accumulation on grassy surfaces, trees, and wires. Again, the Poconos would be the best locale for this.