A quick update- No significant changes since yesterday, except the NAM has been trending towards colder surface level temperatures. QPF values still about 0.80. Timing of precipitation still looks on schedule, with snow starting about 8 AM or so and ending a around sunset.
The unknown is how much dynamic cooling will occur if precipitation rates are high. Still likely to be only grassy surface accumulations, except where elevations are higher and except where bursts of heavier precipitation allows for dynamic cooling. Either way, interesting weather for April.
10AM: This morning’s NAM model has brought the QPF way down to 0.40 inches water. With less precip, there will be less dynamic cooling and even less likely for there to be accumulation.
The latest NAM model data becoming available at this time. (When in Eastern Standard Time, some data is available as early as 9:10, but with Daylight Savings Time, all models are available an hour later local time.).
The latest NAM data shows snow for our area, but again with a fast cut off north and west of PHL. Latest QPF values are in line with last night’s GFS- about 0.21 inches water, mostly falling during the evening hours. 1-2 inches in PHL possible, mostly on grassy surfaces, more in areas of NJ. Snow starts late this afternoon here in PHL and goes through a little after midnight. (Much earlier in Delaware where they may have a more significant accumulation. )
Here’s the NAM forecast map for the 3 hour period prior to 10 PM tonight
NAM Forecast for the three hour period prior to 10PM tonight
Notice how the bullseye for the snow is just east of PHL. Small variations can again blow this forecast.
1PM Update- This morning’s GFS has the precipitation further east and barely reaches PHL. So this could be another zero.
8PM Update- There is some snow falling, but surface temperatures in the region just seem too warm for any accumulation. .
