Monthly Archives: November 2024

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 Weather Outlook

THIS WEEK’S WEATHER

#Philadelphia #weather #PAwx #Drought

Rainfall

Posted Friday 11/15/24 @ 8:34 AM — Yesterday’s high resolution model forecast was pretty good in forecasting the very light precip areas to our west received.

Here’s the MRMS rainfall summary—

MRMS estimated actual total rainfall for Thursday night (Click on image for a larger view.)

We could really use some rain, but it looks like we’ll need to wait until next Wednesday -Thursday (if we’re lucky) to receive any.

Thursday Precipitation Update

Posted Thursday 11/14/24 @ 3:00 PM — Several of the latest high resolution models (HRRR, RRFS) have moved the light precipitation this evening slightly eastward, perhaps giving more of the western suburbs of Philadelphia a bit of much-needed light rain.

Here’s the latest HRRR—

11-14-24 18z HRRR total rainfall Thursday evening/night. (Click on image for a larger view.)
No Rain Today But Possible Pattern Change

Posted Thursday 11/14/24 @ 10:07 AM — All models, including those late to this forecast (ICON, HRDPS), have come together for a cloudy but dry forecast for the immediate Philadelphia area today and tonight.

Another front moving in late Monday may also meet the same fate of a mostly dry frontal passage. This is all due to an upper anti-cyclonic flow over us that has persisted—

ECMWF-AIFS forecast for late Tuesday Note the curvature of the orange arrows, depicting a flow that has an anticyclonic curvature, causing downward vertical motion and works against rainfall. However note the plunge of colder air in the Midwest which should result in at least a temporary change in the position of the jet flow and set up a cyclonic flow over us late next week. (Click on image for a larger view.)

Note the plunge of colder air in the above graphic which should result in at least a temporary change in the position of the jet flow and set up a cyclonic flow over us next Thursday or Friday. Additionally, high pressure in the western Atlantic is setting up further southward. This system has been blocking rainfall in our area, but may finally lose its grip if it sets up further southward. Much of this change is simply seasonal, as colder air builds in the polar areas.

Unfortunately, I’m not sure that any new pattern setting up will be persistent, so any change to colder (and possibly stormier weather) may not last more than a week or two.

No Rain for Thursday Evening. Another Tropical System?

Posted Wednesday 11/13/24 @ 10:45 AM — Last night’s models have continued a trend set by the ECMWF, where any rain Thursday will stay west and south of our area.

Here’s the latest model blend (NBM)—

11-13-24 12z NBM accumulated Precipitation Thursday night (Click on image for a larger view.)

The National Hurricane Center is keeping its eye on the Caribbean for a likely hurricane to develop and hit the Yucatan, then likely dissipate with its moisture eventually brought up along the US southeast and east coast early next week.

Here’s the latest AIFS —

ECMWF-AIFS forecast for next Tuesday night. (Click on image for a larger view.)

This is just one of many possible scenarios with this developing tropical system.

Any Rain Thursday?

Posted Tuesday 11/12/24 @ 10:03 AM — Low pressure is expected to develop later Thursday off of the North Carolina coast.

Depending on the model, the Philadelphia area will be in the periphery of the precipitation shield, with the latest ECMWF keeping us totally dry while the GFS, Canadian and NAM-Nest have us receiving anywhere from 0.05″ to 0.20″ of rain Thursday night.

If the ECMWF is correct, the Eagles game will be rain-free. Otherwise, light rain possible during the game. I’m leaning towards the very light rain forecast.

Here’s the latest model blend (NBM) which shows the periphery of the rain shield—

11-12-24 12z NBM total precipitation forecast for Thurday night (Click on image for a larger view.)
Our Drought Continues

Posted Monday 11/11/24 @ 4:04 PM — For the past several days, it looked like we might get some rain on Thursday. Over the past day, the chance of any significant rain on Thursday is now looking unlikely. Any rain here late Thursday will be light.

An expected low pressure system now looks to develop too far to our south and east—

NAEFS model statistical “average” version with overlayed GEFS model “bias-corrected” precipitation forecast for Thursday. Orange arrows depict the mid-level ridge expected to move in. (Click on image for a larger view.)

With the exit of this low on Friday, a strong mid level ridge with warmer temperatures will move in for next weekend. And more dry weather.

Low End of the Forecast Range

Originally Posted Mon 9:40 AM — Last night’s rainfall was in the low end of the forecast range, closer to the Canadian models and somewhat disappointing compared to the HRRR, RRFS and GFS forecasts.

Here’s the MRMS precipitation totals from last night—

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)      (Click on image for a larger view.)

Following several additional days (today through much of Thursday) of nice weather, we’ll see another chance for rain late Thursday evening.

11-11-24 06z GFS forecast for Friday at 1 AM (Click on image for a larger view.)