So, the models didn’t get it right today and the forecasts were off (including my own), but a postmortem shows the NAM probably did the best in retrospect regarding the precipitation being suppressed to our south.

But here we go again- the NAM is showing a second impulse to develop and intensify off the coast Sunday afternoon and evening.  QPF values over 0.32 inches water.

This time, temperatures will be cold enough for accumulation and the bulk will occur after dark Sunday evening.  This afternoon’s GFS was suggesting this as well (but I had discounted it because of how poorly it modeled today’s weather.)

Like today, a 25 mile error in the extent of the precipitation shield will make or break this forecast.  But if it verifies, we could wake up to 1-3 inches of snow Monday morning, mostly on grassy surfaces .  Of course, it will all be gone quickly.

Sunday 8AM:  Last night’s models continue with the likelihood of snow later this afternoon and the first half of Sunday night.  Differences exist between the GFS and NAM, with the latest NAM showing a period of heavy snow this evening.  Not ready to go with that scenario, but an accumulation of 1-3 inches is possible by daybreak Monday morning, more if the NAM continues its trend.

Of course, things didn’t play out yesterday, so can we trust the models today?

The heaviest precipitation was expected to be just south of PHL and the precipitation cut off north of PHL is sharper than I would have guessed today.

(I use KPHL, the gridpoint for Philadelphia airport for my data. Several data packages, especially the NAM FOUS  are specific for this grid point. It usually serves me well, but not with a sharp cutoff like today.)

So, I’ve been waiting for something to fall from the sky today and here in the northwest part of city, we’ve had nadda.  But radar shows precipitation just south of the city.

The latest NAM data (for KPHL) has gone back to a low QPF, about 0.11.   If we’re going to see anything, it would be between now and 9 PM.