Broad Street Run Forecast Update- We had a little more sunshine than predicted this morning. I’m always glad to be wrong about this. Cloudiness did move in during the afternoon.
Some showers will be moving in Saturday evening.
For tomorrow, Sunday, the models continue with a break in precipitation during the morning hours for the Broad Street Run. Minimal precipitation expected in the morning hours (QPF< 0.01 inches water) but rain returns after 2 PM.
It will be cloudy, cool with high temperatures in the mid 60s and a breezy north to northeasterly wind.
Experimental GFS model- Accumulated precipitation during the morning hours 8AM to 2PM Sunday. Most models keep the immediate PHL fairly dry in the morning hours.
While the operational models (NAMGFS) maintain dry conditions in the morning, the statistical models maintain a chance of light precipitation during the morning. (12Z-18Z)
Ensemble Kernal Density Model Output Statistics (Experimental)
A frontal boundary will pass through our area this evening. Some light showers are possible with the frontal passage.
The front is expected to stall to our south on Saturday, Cloudy conditions are expected, but most of Saturday should be dry. High mid 70s.
Showers develop during the late afternoon or evening Saturday as winds shift to the east and some over-running moisture develops across the stalled front to our south.
On Sunday, as high pressure builds to our north, an easterly flow will bring damp conditions and intermittent drizzle on Sunday. Low level cloudiness and cooler temperatures in the 60s are expected.
Confidence in the degree of cloudiness and the amount of precipitation on Sunday in a bit below average. There are large differences between the GFS and NAM QPF forecasts.
Experimental GFS forecast Sunday afternoon shows a gap in the precipitation shield in our area.
A new feature- in addition to my regular Friday evening weekend weather forecast, I’ll be offering a mid-week weekend weather outlook. An outlook is different than a forecast- it identifies likely weather conditions, but it doesn’t get too specific.
And here it is, based on review of several experimental statistical models and the operational GFS…
A cool front will move through late Friday afternoon and evening as an upper trough builds in for the weekend. The front stalls to our south.
The upper cyclonic flow combined with the stalled front will give unsettled conditions for Saturday and Sunday. A mix of sun and clouds with the chance of showers, especially late afternoon on Saturday and Sunday. It’s not a washout by any standards.It’s more an issue of “self-destructive sunshine” as any sun may trigger clouds and scattered showers due to instability. Again, showers most likely in the late afternoon. Highs in the mid-70s.
The exact location of the stalled front will play a large role in how inclement the weather gets. The timing of upper air disturbances will also affect the forecast.
Thurs AM update- Things already have changed. The front stalls closer to our area. Saturday has increasing chance of rain in the afternoon. Sunday is looking to be cloudy with rain.
