The latest model NAM just becoming available. Here are the trends for Philadelphia and immediate suburbs –
- Last night’s GFS and NAM runs were similar. This morning’s NAM is warmer and faster.
- There’s a trend towards a warmer storm, partially due to track change but also due to less intensification, less phasing of jet streams.
- Earlier start and earlier end of precipitation.
- While I have no expertise, I think the “flash freeze” hype has been just that, and it was likely hype as early as yesterday’s model forecasts showing the precipitation ending before the frontal passage.
- Rain ends about 8-9 AM Sunday.
- Temperatures drop to freezing about 1 PM and continue to drop
Here are the specifics: Precip starts 3-5 PM. Some light snow possible at start, but a very quick change to sleet and then heavy rain. Little or no accumulation.
Heavy rain through 8 AM Sunday. Temperatures rise into the 40s or near 50. Rain ends 8-9 AM Sunday. Cold air delayed and moves in several hours after rain ends, significantly reducing the chance of a flash freeze. Very windy! Temperatures drop to freezing about 1-2 PM and continue dropping into the 20s. Near 10 at night.
Regarding the “flash freeze”, I think it became its own reality when the models predicted no frozen precipitation falling with when the front moved through. In my mind, a flash freeze occurs where there’s still active precipitation when the temperatures drop rapidly to below freezing. Sure, any standing water will freeze. Is that a “flash freeze?”