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Friday Update
Posted Friday 05/30/25 @ 9:53 AM — The clouds should break for sunshine from west to east about 11 AM to noon. Cloudiness develops again about 4-5 PM. Light rain moves in about 7-9 PM. Heavier rain and possibly severe thunderstorms move in about 9 -11 PM Friday evening, according to the latest HRRR.
(Problems with NOAA’s supercomputers have been an issue over the past 18 hours, hopefully resolved. This has prevented availability of the RRFS and REFS.)
Update Thu 5/29 10:44 PM — Tonight’s early models suggest that Friday will be relatively rain free. Minimal isolated showers. Heavy rain and potentially severe storms move in and develop in place over our area beginning 6-8 PM.
Active Unsettled Weather Friday Saturday
Posted Thursday 05/29/25 @ 5:27 PM — Several pieces are coming together for some active weather (heavy rain, thunderstorms) beginning later Thursday night through at least Saturday.
The jet stream is forecast to dive south into a sharp trough (somewhat unusual for late Spring). This feature along with a southern stream jet flow will provide energy to spawn low pressure, rain and thunderstorms. Add to this an increasingly moist air flow with some forecast helicity, wind shear and the ingredients are in place for potential severe weather and heavy rainfall.
Timing of these soon-to-be spawned low pressure waves will be less than exact. As mentioned, the first wave moves through Thursday night with showers and some thunderstorms, ending early Friday morning.
A break in the action looks likely Friday morning, but there’s the possibility of some scattered storms forming Friday afternoon. The heavy action now appears to occur Friday evening and night, where severe thunderstorms are possible, especially in NJ. Rain and thunderstorms continue into Saturday. We may get a break on Sunday.
I expect to hear a few severe thunderstorm announcements over the next two days. Stay tuned.
Clearing Thursday- Possible Severe Storms Friday Afternoon
Posted Thursday 05/29/25 @ 8:42 AM — Sky conditions are expected to improve over this afternoon. Cloudiness will become quite variable in many areas between 2 and 5 PM. Enjoy while you can.
More clouds and what looks like possible severe storms Friday afternoon into Friday evening.
Wednesday -Thursday Update
Posted Wednesday 05/28/25 @ 4:33 PM — I rarely use the popular TV weather phrase “I’m tracking this [on radar]” to describe the progression of weather.
“Tracking” suggests to me a very non-dynamic process with weather moving from point A to point B, like on a train track. Indeed, the hourly rain depiction on the iPhone weather widget is that level of weather ‘forecasting’. Weather forecasting is much more complex than this.
Case in point is the current radar, which shows the back edge of the rain moving towards us at 4 PM. So, why did they postpone the Phillies game for this evening?
The reason is rain is expected to redevelop over us and increase in intensity despite the back edge visible on radar at this time.
The above radar image above includes RAP model vertical velocity (yellow X) which is expected to move over us during the early evening hours. Heavier rain is expected to redevelop with this dynamic in place Wednesday evening. (I guess we’ll see if it happens.)
The rain is expected to depart by the early morning, but low clouds will linger for much of the day Thursday.
Another possibly heavy rain maker is forecast to begin mid afternoon Friday.
Wednesday’s Rain
Posted Tuesday 05/27/25 @ 6:10 PM — This afternoon’s models are predicting remarkably similar rainfall totals for Wednesday, with higher rainfall to our south (a trend that has been consistent as well.)
To mix it up a bit, here’s the HREF ensemble model rainfall totals through 8 AM Thursday—
With the exception of the Canadian RGEM, most models have rain starting around daybreak Wednesday. As for the Phillies game Wednesday evening, it looks like the rain doesn’t taper until late evening.
The rain ends early Thursday morning, but plenty of clouds are forecast for much of the day, possibly breaking to some sunshine or bright skies late Thursday afternoon.
Tuesday-Wednesday Forecast Update
Posted Monday 05/26/25 @ 7:29 PM —It appears that cloudiness will advance earlier into our area Tuesday than previously forecast. Considerable cloudiness is expected during the morning, with thickening and lowering cloudiness during the day.
Many models have some light sprinkles after midnight into early Wednesday morning with heavier rain developing by late morning and during the afternoon. An easterly wind will make it quite chilly on Wednesday.
Rain will continue Wednesday evening and taper off Thursday morning. Slow clearing with a chance of a shower through Thursday.
The GFS, Canadian, ECMWF and RRFS are forecasting close to 1+ inch of rain total around Philadelphia, less amounts to our north. The AI versions of the ECMWF and the GFS show lesser amounts, about 0.5-0.75 inches with the heaviest rain south of our area.
Memorial Day through Wednesday
Originally Posted Sun 7:53 PM —Low pressure that slowly departed our area will still influence our weather on Monday, Memorial Day. We’ll see plenty of sunshine Monday, but several models are hinting at some cloudiness developing mid-afternoon into the evening as a short wave associated with the departing low rotates through.
The GFS and pre-release RRFS model show the possibility of a few isolated showers between 3 PM and 8 PM. Most areas will be dry. (The Canadian HRDPS keeps these showers far north of our area.)
(Updated Sunday 05/25/25 @ 9:12 PM —Several more of this afternoon’s models keep any isolated showers to our far north.)
Tuesday will have sunshine through high cirrus clouds ahead of an approaching low pressure system. (Areas south of the city and in South Jersey may have considerable mid-level cloudiness.)
Here’s the storm taking shape in the Central US as of Sunday evening —
This storm will bring rain to our area Wednesday. The trend has been for the heaviest rain to move to the south of our immediate area. About 0.5 inches of rain are expected.
