Posted Friday 04/11/25 @ 1:49 PM —An upper closed low pressure system will bring rain and chilly conditions, as it keeps the surface low developing off the coast from exiting.
Rain Friday night into much of Saturday. Here’s the ECMWF-AI forecast for 2 PM Saturday—
ECMWF-AI forecast for 2 PM Saturday. The Blue L is the upper low which will sit directly over our area. Rain much of the day, tapering later in the day. (Click on image for a larger view.)
By Sunday, the upper low has moved off the coast but a cold pocket of air aloft (red thickness contours) will keep cloudy skies. A shower can’t be ruled out. An inch to two inches of rain is currently forecast.
ECMWF-AI forecast for 2 PM Sunday. Rain has for the most part stopped, but the red thickness lines indicate cold air aloft that will keep things fairly cloudy. (Click on image for a larger view.)
The ridge developing in the Central US will bring milder temperatures and better weather next week.
For a part of April, this blog’s weather updates will be less frequent than usual.
Posted Thursday 04/10/25 @ 10:29 AM — In contrast to some of the forecasts I’ve heard this morning, based on the experimental RRFS and the AI version of the ECMWF, it really looks like any rain here in the immediate Philadelphia area will occur AFTER 5 PM and perhaps not even during the evening hours. Any rainfall we do receive today looks to be very light.
06z RRFS (experimental) simulated radar/rain forecast for 5 PM Thursday. (Click on image for a larger view.)
Posted Wednesday 04/09/25 @ 11:41 AM — Depending on the model, it appears that rain will move in Thursday evening and will be on and off through Friday. Rain picks up in intensity later Friday evening as low pressure develops near the coast and likely lasts through much of Saturday.
A closed upper and mid-level low pressure system will remain over our area through the weekend. Cooler than average temperatures and unsettled conditions are likely.
The experimental RRFS model is handling Friday night quite differently compared to the ECMWF-AI model; the RRFS has a prolonged break in the rain later Friday afternoon into the evening and then has the rain picks up later that night. It will be interesting (experiment) to see if this holds.
06z RRFS-A model forecast for 7 PM Friday evening. The low pressure system expected to form along the coast is just taking shape well to our south Friday evening. (The majority of the other models, including the AI models, have heavy rain moving in in this time frame) (Click on image for a larger view.)
For part of April, this blog’s weather updates will be less frequent than usual.
Showers Drizzle But Really not much Rainfall
Posted Monday 04/07/25 @ 5:39 PM — Despite all the clouds, fog, drizzle and showers/rain we had over the past several days, many areas did not receive much need accumulated rainfall. Here’s the 72 hour totals—
MRMS rain-gauge measured rainfall combined with rain-gauge calibrated and interpolated radar-based summary of ACTUAL RAINFALL RECEIVED. Color shading is in inches. Line contour numbers are in mm. (25.4 mm= 1 inch) Over past 72 hours. (Click on image for a larger view.)
The system will slowly exit tonight and Tuesday should become windy, partly to mostly sunny and cold. Highs in the low to mid 40s.
Previously Posted Sun @ 7:43 PM — —The slowly moving cold front that passed through today will spawn another low pressure system tonight into Monday. Cold air will filter in behind this low.
It should be noted that while several models were originally forecasting some clearing Monday afternoon, while the ECMWF-AI model has consistently delayed that clearing until Monday evening. Monday should remain cloudy with showers, with diminishing coverage and intensity during the afternoon hours.
ECMWF-AI forecast for Monday at 8 PM. (Click on image for a larger view.)
A well-advertised dip in the jet stream will occur over the Northeast this week following Colder than seasonal averages are expected.
Another storm is expected Friday into Friday night.
For part of April, this blog’s weather updates will be less frequent than usual.
Disturbances moving along a somewhat stationary warm frontal boundary to our south will continue to affect our weather this weekend.
There won’t be much in the way of sunshine this weekend, as low clouds, rain, drizzle and thunderstorms will each make an appearance through Monday.
An easterly flow will develop ahead of a somewhat stationary warm front on Saturday. Some rain and showers will move through from the southwest before daybreak Saturday. There’s a range of model forecasts, but most have this rain somewhat heavy in the early morning, tapering off about 10 to 11 AM.
(If the warm front actually moves north of our area, we may see some slight clearing, but it appears the warm front will stay to our south. Below is the latest ECMWF-AI model—
ECMWF-AI Forecast for 2 PM Saturday. Rain lifting off to our northeast, but the front appears to be to our south. (Click on image for a larger view.)
It should be noted that the experimental RRFS, which resumed running this week, has most of this early morning activity well north of the immediate Philadelphia area. The NAM-NEST, the HRRR, and another experimental model, the MPAS, has the heavier rain right over Philadelphia early in the morning. It will also be windy in the morning.
Most models maintain low clouds, drizzle and even some fog for much of the day but especially late Saturday afternoon, after 4 PM and into the night.
Low pressure develops along the warm front to our south and lifts away on Sunday, shifting the winds to the north on Sunday as rain and even some thunderstorms in the early afternoon. Another low pressure system moves through along the stalled front from the west late Sunday afternoon with heavier rain into Monday.
Some of the timing of these features may change based on slight movement of the somewhat stationery front.
