A weak warm frontal pattern will develop today as high pressure moves slowly off to the east and the upper air trough responsible for the unseasonably cold weather finally de-amplifies.
With the return of somewhat milder air aloft, there is an expected development of mid-level clouds– altocumulus and altrostratus – that will give a continued grey, November feel to Saturday.
So Saturday will be mostly cloudy, some breaks of sun possible, a bit milder but still unseasonably cold with a high temp near 40.
Winds shift to the southwest tonight and milder temperatures are expected on Sunday with highs in the low 50s. There may be some low level clouds at times, but much more sun than Saturday.
The storm today, which had always looked primarily like a rain maker here in Philly, appears to be even warmer than expected. Heavy rain most of the day….changeover to snow in the immediate PHL area late afternoon or after dark now. About 1 wet inch accumulation most likely.
Don’t let those TV weathercasters fool you. There weren’t any last minute changes they “tracked”. This wasn’t ever going to be a “snow shhtorm” They’ve been hyping the snow potential of this storm since Sunday, even when all indications were that it would be a mostly rain storm all along right in PHL.
The latest NAM and GFS models are wetter and warmer than previous model runs. Very heavy rain expected most of the day, changing to wet snow about 2-4 pm before ending early evening. Much of the snow won’t accumulate.
Temperatures don’t support much accumulation, both at the surface and a few thousand feet up. Still 1-2 inches most likely on streets and sidewalks, a bit more on grassy surfaces.
The NAM and GFS continue to predict different scenarios for the coastal storm tomorrow, Wednesday.
The NAM predicts amost twice as much precipitation with more falling as snow. The GFS has warmer temperatures at the surface and delays changeover to snow until late in the afternoon, as the amount of precipitation (QPF) winds down.
The NAM has often overstated QPF in past storms. So I’m going with the GFS model, which has a changeover to snow between 2-4 PM and conditions allowing accumulation after 4 PM. Still going with 1-2 inches of snow for Philadelphia and the immediate suburbs. Further NW, greater amounts possible.
The new models come out about 10:30 PM. I’ll update if things look different.