The first significant dip in the jet stream for this fall/winter season will occur this weekend for the northeastern US. A cyclonic flow of cool/colder air will bring temperatures down to about 40 or less at night and the 50s during the day.
While the predicted upper air jet pattern has been consistent, the models have shown great variation with the possibility of upper air disturbances embedded in the flow. What this means is that it’s not a certainty how much sunshine we’ll get with these cooler temperatures.
Periods of sun and cloudiness looks to be the best bet, and there’s a slight chance of a quick sprinkle during the afternoon on Saturday and even moreso later Sunday afternoon and evening, as the upper flow changes to the southwest. A brief snow flurry Sunday night isn’t out of the question.
A cold front moved through this evening (Friday) and cooler, more fall-like temperatures will be apparent Saturday. Plenty of sunshine will allow temperatures to get into the mid 60s on Saturday.
The pattern will be very progressive and a return flow of milder air will make Sunday (and Monday) beautiful with sunny skies and highs in the 70s.
Last night’s NAM did better than the GFS model with the rain tapering early this morning and accurately depicted the movement of the heavy continuous rain to the western part of the state. #pawx
Today’s HRRR model run, based on the NAM, maintains most of the rain in western PA; in the PHL area, clouds with scattered, intermitten light rain showers possible through the evening. The winds, with gusts, will continue. Highs will be around 54.
Sunday looks to be cloudy, but skies will be brighter and high temperatures will be in the 60s. Still a slight chance of a brief sprinkle on Sunday.
