Category Archives: Philadelphia Weather Outlook

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.)

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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#Philadelphia #weather #PAwx #drought

Philly Drought Watch

Posted Friday 10/25/24 @ 11:28 AM — Our next chance of any rain appears to be the first few days of November. Unfortunately, the latest AI and ensemble models show an upper air ridge in our area that may seriously reduce the amount of rainfall we get ahead of a cold front.

Here’s the ECMWF-AIFS forecast for November 2

ECMWF-AIFS (Artificial Intelligence Model) forecast for 8 PM Saturday Nov 2nd. Light showers ahead of a cold front, dissipating as they move eastward. (Click on image for a larger view.)

Here’s the GFS AI model forecast for Sunday Nov 3rd—

GFS Graphcast AI Machine Learning Model forecast for Sunday Nov 3 at 7 PM. Again, upper ridge will reduce our rainfall potential. (Click on image for a larger view.)

On the more positive side is the NAEFS (ensemble model combined GEFS and Canadian ensemble). It’s forecasting more rain and possible coastal tropical system near Florida. Likely not correct—

NAEFS forecast for Wednesday Nov 6th . Tropical system hinted at near Florida coasts. (Click on image for a larger view.)
The Drought Continues

Posted Thursday 10/24/24 @ 5:01 PM — I can’t remember the last time I saw so many large sprawling high-pressure systems on the weather map. Our dry weather is expected to continue into the first few days of November.

Until that time, we’ll have some colder periods towards the end of this weekend as a second cold front moves through early Saturday. We’ll see another warm-up next week. And mostly sunny skies shall prevail.

I may have to rename this blog, “The Rain Watch”. I’m currently using various statistical ensemble models and the ECMWF-AI and GFS-AI models to see about our next chance of rain

We may finally get some rain, albeit, hardly a drought-buster, sometime in the November 3rd through November 5th time frame.

Here’s the ECMWF-AIFS forecast for November 3—

ECMWF-AIFS forecast for 7 AM November 3. A cold front moves through with about a quarter inch of rain, possibly more if low pressure develops along the front. (Click on image for a larger view.)

Posted Tuesday 10/22/24 @ 4:27 PM — As mentioned yesterday, two cold fronts will move through in the coming days; one late Wednesday night into Thursday and another late Friday night into Saturday.

These frontal passages have been forecast to be dry, but today’s ECMWF and Canadian RGEM show a deeper trough moving through with enough lift for with some sprinkles, mainly in NJ late Wednesday night. The few sprinkles forecast are supported by the experimental REFS. (The ECMWF-AIFS shows no showers.)

We’re only talking a one or two hundredths of an inch in a few locations.

During the weekend, our current well above average temperatures will drop to noticeably cooler levels.

The GraphCast AI-Machine Learning version of the GFS has moved the chance of rain here further down the road into November from yesterday’s forecast. So the drought continues.

10-22-24 00z Graphcast-GFS forecast for Monday, November 4th. Our first chance of light rain?? (Click on image for a larger view.)
No Rain

It’s been a long time since things seemed so dry outside. And the current extended range forecasts keep thing dry for us over the next two weeks!

Yes, there will be two cold fronts moving through this week. The first one will result in a familiar pattern of having any rain shear off to the far north and west of the city—

Today’s ECMWF shows showers only far north of the city. (Click on image for a larger view.)

Another cold front moves through Saturday. The models had been forecasting some light showers for us, but those have all but disappeared in the forecast—

Today’s GFS forecast for Saturday. Grey black is cloud cover. Essentially no rain with this front. (Click on image for a larger view.)

I’m still playing with the highly experimental AI-Machine Learning version of the GFS. It still seems to show the first chance of any substantial rain here is November 3rd!

Graphcast GFS (AI Machine Learning model ) forecast for November 3rd. (Click on image for a larger view.)

All I can say is “Wow”.