Update Sat 8/24 10:39 PM — A few models are showing widely scattered showers Sunday evening, dissipating just as they approach Philadelphia. The NAM-NEST and Canadian models have been consistent with this forecast, the HRRR, ECMWF and GFS show no showers. So just a possibility about 8 PM. Also, expect a fair amount of wildfire smoke haze in the afternoon.
Originally Posted Fri 7:34 PM —A somewhat blocked weather pattern continues and we will continue to be in a dry, sunny stretch of weather through the weekend.
NAEFS jet stream level winds (300 mb) forecast for Sunday shows our area under a cool flow associated with an upper trough, while the mid section of the country remains under a hot ridge.
Showers are not expected until late Monday, and not all models are on-board with that.
Originally Posted Fri 7:34 PM —
Saturday Forecast
Sunny and pleasant.
NBM high temperatures: Blue Bell, PA 84º Philadelphia, PA 85º Uncertainty (based on standard deviation): average ± 1.2º
Sunday Forecast
Sunny and warmer. A few scattered clouds in the late afternoon.
NBM high temperatures: Blue Bell, PA 87º Philadelphia, PA 88º Uncertainty (based on standard deviation): average ± 1.7º
Posted Thursday 08/22/24 @ 5:20 PM — Sunny skies with a gradual increase in temperatures through Sunday. Here’s the latest NBM temp and dew point forecast in the form of a meteogram —
08-22-24 18z NBM temperature and dew point meteogram forecast for Philadelphia (Click on image for a larger view.)
First chance of any precipitation, may be Monday, late afternoon or evening.
Quiet Week Weather-wise
With an upper trough and corresponding surface high pressure system in place, our weather is spectacular, but a bit cool. (Current seasonal average highs are 82º Blue Bell, 83º Philadelphia.) We’re also seeing a bit of instability cloudiness at times.
As for that storm that threatened on Monday, here is a photo of what looks almost like a shelf cloud associated with a thunderstorm just northwest of my home at 6:30 PM Monday—
Not exactly a shelf cloud, but close. (Click on image for a larger view.)
Forecast Update
Posted Monday 08/19/24 @ 8:47 PM — Well, a wave has developed on the front and some showers are expanding in coverage just northwest of the city. Apparently predicted by the NAM-NEST and the HRDPS. May move in over the next hour. Very interesting.
Posted Monday 08/19/24 @ 4:37 PM — Today’s forecast line of showers and thundershowers fell apart and went to our north and to our south. Current radar shows some other activity but winds have shifted and I wouldn’t count on any significant showers in the immediate Philadelphia area. Here’s the current radar at 4:30 PM—
NEXRAD composite radar 4:30 PM. While some showers are hanging back, I’m not convinced we’ll see much here at this point. (Click on image for a larger view.)
For the balance of the week, an upper trough will allow cool high pressure to build in through the weekend. Sunny skies and unseasonably cool weather is expected for the next several days. The NAEFS shows the forecast jet stream position on Thursday—
NAEFS jet stream position for Thursday. Upper low pressure will allow surface high pressure, keeping us dry and mostly sunny. The 576 thickness line (orange) which is a useful demarcation of the heat dome is very far south of us. (Click on image for a larger view.)
Mostly sunny and dry through the week. The upper low can cause some instability cloudiness at times, especially in the afternoons and some difficult to time disturbances may rotate around the upper low. But overall, quite nice for an extended period of time.
Just speculation, but I expect the heat dome to return by the end of August or the beginning of September.
Monday Forecast
Originally Posted Mon 8:41 AM — A strong cold front will move through our area late this afternoon preceded and accompanied by showers and some thunderstorms. Gusty winds expected but severe weather not expected at this time.
Prior to the showers/storms, expect some sunshine.
Current timing is between 4 PM and 8 PM. Here’s the RRFS simulated radar forecast for 4 PM—
06z RRFS simulated radar forecast for 4 PM Monday. (Click on image for a larger view.)
