A weak low pressure disturbance will move along a frontal boundary just to our south late Saturday afternoon.
There are increasing signs that a last minute intensification will occur as the disturbance reaches the coastline.
If this occurs in the evening rather than during the daytime hours, the high March sun angle won’t be a factor and some snow accumulation is possible. Current NAMQPF values are about 0.33 inches water. Current thermal profiles support the precip falling mostly as snow, but light QPF in March can be difficult to accumulate, unless it occurs at night.
Each recent successive model run has shown slightly greater intensification. Not a sure thing, but it needs to be watched.
The long range models are suggesting a continued overall somewhat cold pattern with another deep cold outbreak the end of next week, followed by moderating temperatures.
The latest NAM data is in and it shows the precipitation taping off and ending between 12 and 2 PM in PHL and its immediate suburbs, with just lingering snow showers possible from wrap-around moisture. Winds will pick up.
Surface temperatures are predicted to drop by 2 PM, as well as temperatures in the upper atmosphere.
A changeover to a bit of snow or snow/sleet mix is possible before ending. BUT the thermal profiles still favor a precipitation mix of sleet/rain/snow and upper atmosphere temperatures remain a bit too warm for much snow formation before the precip exits.
Final snowfall/sleet totals won’t be much different than what you see out your window right now. What you see is what you’ll get.
The changeover to sleet, freezing rain and rain has occurred in PHL and the immediate surrounding suburbs and this precipitation type will continue fairly heavy until about 1-2 PM today. What you see is what you’ll get….If you haven’t received heavy snow, you’re not going to.
Winds will pick up with temperatures at or below freezing early, but rising during the morning. Slippery conditions still exist, but roadways may be less impacted than usual with solar insolation through clouds reducing icing on dark asphalt as we approach noontime. A brief changeover to snow at the end of the storm won’t add much accumulation.
When the TV people try to explain what happened to their 10-12 inch forecasts from last night, don’t believe them. The “track of the storm” didn’t change. They simply didn’t interpret the data properly.
