Category Archives: Philadelphia Area Weather Forecasts

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#Philadelphia #weather #PAwx #Drought

Forecast Update

Posted Sunday 11/17/24 @ 10:03 AM — A cold front moves through around daybreak Monday morning. We’ll see some high cirrus clouds associated with this front today and especially this afternoon. Sunshine through high clouds is expected, with occasional mixing of mid level clouds.

The ECMWF shows some light sprinkles moving through between 5 AM and 8 AM Monday, although most of the other models keep us dry. The HREF suggests some radar echoes without the sprinkles reaching the ground.

The atmosphere is setting up for an active week by Wednesday. Here’s the current water vapor/radar image/RAP model —

Sunday morning satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. Several low pressure systems (1) and (2) will merge near the Great Lakes by Wednesday and a resulting upper closed low and surface low will be near the Philadelphia area by Wednesday. Additional moisture (3) from a tropical system will stream near us as well. (Click on image for a larger view.)

Additionally, showers from this developing system may move in earlier, as early as Wednesday morning. Stormy and windy by Thursday.

The models are still cranking out about 0.8″ of rain, although the current trend has been towards lower amounts.

Forecast for Rain late Wednesday Continues

Posted Saturday 11/16/24 @ 4:44 PM — Following a beautiful but windy day today, we’ll have another delightful day for Sunday with a layer of high clouds filtering some of the sunshine.

As beautiful as the weather has been, we really need some rain. I’ve been keeping my eye on a seasonally induced pattern change with a dip in the jet inducing low pressure development in a location favorable for rainfall here.

The latest operational, ensemble and AI models continue with a forecast of rain, beginning Wednesday evening and continuing through part of Thursday. Most models are currently forecasting anywhere from 0.8″ to 1.2″ of rain in the immediate Philadelphia area and areas west and northward. Similar amounts to our east in NJ.

Unsettled, windy and much cooler weather is likely for later Thursday into Friday.

Here’s the latest ECMWF forecast—

11-16-24 12z ECMWF forecast for Thursday morning. Low pressure develops directly over our area. (Click on image for a larger view.)

We’ve been disappointed several times over recent months regarding rainfall, but I think, “this time is different”. (Famous last words.)

The consistency and continuity of various model forecasts for rain this time is encouraging. It’s also possible that some moisture from the tropical system in the Gulf may be brought into play.

Stay tuned for updates.

Originally Posted Fri @ 6:06 PM — —High pressure builds in for this weekend. An approaching cold front will bring sunshine through high clouds Sunday afternoon. As has been the case over recent months, no rain is expected here with this frontal passage on Monday.

A seasonally driven pattern change is forecast by numerous models next Wednesday into Thursday, with the jet flow dipping south to our west and spawning surface low pressure in a favorable position to give us rain! I’ve seen these potential rain-makers fall apart in recent weeks, but this one is currently looking likely—

Latest ECMWF for next Thursday early morning—

11-15-24 12z ECMWF forecast for Thursday at 4 AM (Click on image for a larger view.)

Here’s the latest available GFS – AI model forecast for early Thursday, also supported by the latest GFS—

11-15-24 06z Graphcast-GFS AI model forecast for 4 AM Thursday. (Click on image for a larger view.)

I’ll keep an eye on this over the coming days.

Saturday Forecast

Sunny and windy/gusty, especially in the afternoon.

NBM high temperatures: Blue Bell, PA 60º Philadelphia, PA 62º
Uncertainty (based on standard deviation): low uncertainty ± 0.8º

Sunday Forecast

Sunny in the morning, then mostly sunny through high clouds in the afternoon. There may be some mid level clouds at times.

NBM high temperatures: Blue Bell, PA 60º Philadelphia, PA 63º
Uncertainty (based on standard deviation): low uncertainty ± 1.2º

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#Philadelphia #weather #PAwx #Drought

Sunday Evening Rain Update

Posted Sunday 11/10/24 @ 10:10 AM — Things still look good for an end to the dry period we’ve been in here (although, tonight will not be a drought-buster). The models have trended upwards in the rainfall amounts and many areas may see 0.5″ –0.6″ or more this evening and tonight. Rain expected to move in between 6 PM and 8 PM.

Here’s the latest Water Vapor/Radar image—

Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. (Click on image for a larger view.)

The latest HRRR is below—

11-10-24 12z HRRR total rainfall tonight. (Click on image for a larger view.)

Not posted is the latest RRFS which had many areas receiving in excess of one inch of rain here. (Probably not correct, but we’ll see if they corrected the excessive rainfall bias for this still experimental model.)

Additional rainfall expected here Thursday!

Sunday Evening Rain Update

Posted Saturday 11/09/24 @ 3:25 PM — It’s been an awfully long time since I posted a rainfall forecast, but it looks very likely that we’ll get some rain in the Philadelphia area Sunday evening and night.

As always, the models show a range of rainfall totals and distributions, but most models are between 0.25″ and 0.60″ with 0.30″– 0.40″ being solid bet. Today’s models are showing light rain to start in western areas around 6 PM and it moves into Philadelphia and then NJ about 8 PM or so.

Before then, a mostly cloudy to cloudy day. (Can’t remember the last time we had a cloudy day!)

Here’s the latest HRRR rainfall forecast which is running a bit higher than the NBM and RRFS totals—

11-09-24 18z HRRR total accumulated rainfall Sunday night. White contours are 0.1″ increments The rain ends around daybreak Monday. (Click on image for a larger view.)

We have another chance of rain Thursday.

Originally Posted Fri 10:23 AM —High pressure will continue to provide beautiful weather through Saturday, although it appears that it might become quite windy at times, especially Friday night.

An approaching low pressure system will pass to our north and a warm front followed by a cold front will move through Sunday night.

Friday morning Water Vapor/Composite Radar with superimposed RAP model thickness (500-1000mb- yellow contours) and potential vorticity (violet lines) (Click on image for a larger view.)

Following a sunny day Saturday, Sunday will be mostly cloudy. Rain should hold off until 4-7 PM

It had appeared that moisture from Rafael might enhance the rainfall here, but that is appearing less likely as the hurricane is forecast to to remain in the Gulf and gradually dissipate.

Total rainfall looks to be in the 0.3″ to 0.5″ range by Monday morning with the larger amounts west of the city. Hardly a drought-buster but better than nothing. There’s another chance of rain next Thursday.

Saturday Forecast

Sunny and somewhat breezy.

NBM high temperatures: Blue Bell, PA 56º Philadelphia, PA 58º
Uncertainty (based on standard deviation): ± 1.3º average to low uncertainty. Average seasonal high temp is 56º

Sunday Forecast

Cloudy and increasingly windy. There may be some breaks of sun through high clouds mid-day. Light rain develops west to east from about 5 PM through 7 PM and continues into early Monday morning. Windy and gusty at night.

NBM high temperatures: Blue Bell, PA 61º Philadelphia, PA 62º
Uncertainty (based on standard deviation): Low to average uncertainty ±1.2º