The models are showing signs of an evolving pattern change beginning this week. Most obvious will be a developing trough in the the northeastern US giving us much cooler temperatures following a cold front passage tonight.
A cold front moves through tonight. Showers associated with this front will likely stay to our north. A few models vacillate on whether the Philadelphia area will see any showers or sprinkles with an upper air disturbance that moves through Monday morning. If we get anything, it will be scattered and very light.
The upper trough for the first part of this week may cause some instability cloudiness, perhaps more than the models are showing.
With the upper blocking ridge in the central US breaking down by the end of this week, we may finally see some systems by next week bring us some rain. although I don’t see any specific system yet in the extended range models.
Posted Saturday 10/12/24 @ 10:48 AM — Cancel those showers for Sunday night. Both the GFS and ECMWF now show less of an upper trough and weaker low pressure development. The very dry weather to continue.
Originally Posted Fri 5:36 PM —With a high pressure ridge and upper air trough seemingly unchanging in previous models runs, I’ve been taking a break from forecasts for the past two days. However, weather being what it is, things have changed and it seems there may actually be a chance for some rain late Sunday or Sunday night.
We’re expected to be under the influence of an upper trough by Sunday and low pressure is expected to develop right over western Pennsylvania by Sunday evening.
While we’re still not located in the most favorable position for rain relative to the jet flow, the latest GFS is cranking out some rain Sunday night! Not a lot, about 1/4 of an inch, but we’ll take anything we can get.
Saturday Forecast
Sunny and quite nice. Some high thin cloudiness moves in late afternoon.
NBM high temperatures: Blue Bell, PA 74 º Philadelphia, PA 76º Uncertainty (based on standard deviation): High confidence
Sunday Forecast
Considerable cloudiness far northern suburbs, mostly sunny closer to the city. Increasing cloudiness late afternoon. Cloud cover will affect high temperatures reached.
NBM high temperatures: Blue Bell, PA 77º Philadelphia, PA 79º, maybe 80º Uncertainty (based on standard deviation): slightly below average confidence.