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Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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Thanksgiving Day Forecast Update

Posted Thursday 11/28/24 @ 1:42 PM — The rain has tapered off on schedule, about 1 PM. Most of the area received the rainfall predicted, about 0.60 – 0.90″ —

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.)

Based on the models, a considerable amount of cloudiness is still forecast for this afternoon, although the latest satellite image shows building high pressure and breaks in the overcast to our west—

Satellite image 1:41 PM with superimposed HRRR pressure gradient. Negative pressure gradient shows the low pressure system will intensify and move to near Cape Cod during the afternoon. Some breaks in the overcast to our far west may move in earlier than forecast by the models, but never second guess the models. (Click on image for a larger view.)

Colder weather tonight and into the weekend. The latest RRFS (experimental) shows light scattered rain and snow showers Friday mid- afternoon —

Todays’ 12z Experimental RRFS foreasts some scattered light showers and patchy dark low clouds Friday afternoon due to instability. Violet shading shows snow precipitation type. (Click on image for a larger view.)

Note: the RRFS is still experimental but under active development and is increasingly used here for forecasts.

Thanksgiving Day Forecast Update

Posted Wednesday 11/27/24 @ 4:56 PM — The models have come together with the Thanksgiving Day forecast. Rain moves in between 1-3 AM and becomes moderate to heavy during the morning hours. The low pressure system exits and intensifies near NYC .

Rain is expected to taper off and end between 1 and 2 PM. It will still remain quite cloudy. Quite windy conditions develop about noon and continue into the afternoon with gusts 35-40 mph.

11-27-24 18z GFS forecast at noon Thursday. Center of low is over Long Island Sound and drier air shuts off the rain in our area by 1-2 PM (Click on image for a larger view.)

It will get cold Thursday night and colder into the weekend.

Friday starts sunny but instability cloudiness develops late morning and widely scattered rain showers are possible during Friday afternoon, especially northwest of the city. Far northwestern areas may see some snow showers.

Thanksgiving Day Forecast Update

Posted Wednesday 11/27/24 @ 8:27 AM — Last night’s models show a faster moving storm and somewhat lower rainfall amounts for our area.

Most models show about 0.60″ of rainfall, starting about 2 AM Thursday morning and ending about 1-3 PM Thursday. (The GFS continues with about 0.8″)

Here’s the latest RRFS (experimental) model forecast for 2 PM showing the departing rain—

11-27-24 06z RRFS experimental model forecast for 2 PM showing simulated radar/rainfall at 2 PM.(Click on image for a larger view.)

The weather pattern gets cold starting this weekend.

Posted Tuesday 11/26/24 @ 4:44 PM — The cold front moved through this morning and parts of our area had a ‘reasonable’ rainfall, while others did not.

Here’s the MRMS precipitation summary for this morning’s rainfall—

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.)

No significant change in the forecasts from my earlier updates for Wednesday through Friday.

Wednesday starts sunny but will have increasing clouds during the day. By 3-4 PM, it should be mostly cloudy.

Rain starts after midnight or closer to 2 AM Thursday morning. Moderate rain, heavier in the late morning, tapers off during the afternoon and may end as early as 3-4 PM, although the latest NBM has lingering sprinkles through 6 PM or so. Clouds linger into the evening. Windy and gusty!

The models are cranking out a generalized 0.65″ to 0.90″ with the usual scattering of lighter and heavier amounts.

Friday marks the beginning of a colder, mostly sunny and dry pattern that lingers through at least next week. Dry-passage cold fronts will bring high temperatures down quite a bit next week.

Tuesday and Thursday Forecast Updates

Posted Monday 11/25/24 @ 4:57 PM — Little change with the forecast for Tuesday and increasing clarification of the rain forecast for Thursday with a faster exiting storm .

A cold front moves through during the morning Tuesday. Showers will give us about 0.15″ to 0.20″ with the greater rainfall (as usual) falling north and west of the city. Skies clear and sun is expected by the early afternoon. Colder weather moves in for Tuesday night and Wednesday.

Wednesday will have clouds from the city westward in the morning, then increasing clouds west to east throughout our area.

Rain begins a few hours after midnight Wednesday and continues Thursday, Thanksgiving Day. It may be windy and gusty as low pressure intensifies off the NJ coast. Rainfall is consistently forecast to be in the 0.60″-0.80″ range.

For travelers on Thanksgiving, unfortunately it looks fairly rainy and somewhat windy.

Rain may end about 2-3 PM around Philadelphia and towards evening in NJ according to the latest GFS and ECMWF models which is a quicker exit than previously forecast.

Latest GFS with the rain exiting about 3 PM Thursday—

11-25-24 18z GFS forecast for 3 PM. Rain quickly exiting our area. (Click on image for a larger view.)

Dry, windy and colder Friday with periods of instability low level cloudiness

Thanksgiving Weather

Originally Posted Sun @ 8:55 PM — —This week’s active weather pattern will be highlighted by a cold front that moves through Tuesday morning with some showers, followed by colder temperatures. Another highlight will be a storm that approaches Wednesday night into Thursday morning bringing rain to our area.

The models are in good agreement with the cold front passage Tuesday morning. Most are cranking out 0.25 inches of much needed rain with this front. Colder temperatures are expected Tuesday night into Wednesday.

A storm approaches late Wednesday night into Thursday. There’s been considerable uncertainty about both the track of this storm and its intensity. Much has to do with the size and configuration of the mass of cold air that descends down following the cold front on Tuesday.

The AI models have had a faster, more southern track with little intensification of this storm and very little rain for us. The latest GFS is somewhat similar.

However most of the models have moved towards a track that is further north with greater intensification and brings about 0.75 inches of rain for our area.

The latest ECMWF is most aggressive with this system —

11-24-24 12z ECMWF forecast for Thursday morning. This is very aggressive with the intensification and the northward track, but is not necessarily correct. (Click on image for a larger view.)

Since there’s so much spread in the models, I expect there will be further changes in the forecast for Thanksgiving Day. Stay tuned.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Useful Link for the Model Blend (NBM) Data

Posted Saturday 11/23/24 @ 4:56 PM — The NBM is considered one of the best sources of hourly temperatures and winds and rainfall. The NWS has a link for obtaining this data in text format, albeit for local airports ( but not specific locations like Center City as I provided below.)

I’ve pre-configured the link for Philadelphia and Northeast Airports along with Wings Field in Blue Bell.

This link has been shared on this blog before, with explanations and examples to how it uses the GMT time zone (now called UTC or Coordinated Universal Time).

The hourly NBM labeled NBH is very useful once you get used to the GMT (Universal) time. (7AM here is the column labeled 12)

The extended (NBE, NBX) data is less intuitive, since as an example, next Thursday’s daytime data is shown in the column labeled 00z Friday (which occurs at 7 PM EST Thursday). You can find my NBM Text guide here.

Sunday Forecast Update

Posted Saturday 11/23/24 @ 12:06 PM — Latest NBM wind meteogram for grid point Center City Philadelphia and the marathon. Large uncertainty range (dotted lines) on wind gusts.

11-23-24 12z NBM wind meteogram for Center City (Click on image for a larger view.)

I’ve updated the regional rainfall totals map for the past 48 hours here.

Originally Posted Fri @ 6:52 PM — —The deep upper low and surface low exit our area late Friday night. Skies will clear for Saturday with high pressure building in. A weak warm front will bring a mix of clouds and sun Sunday. Clouds decrease during the mid afternoon. I’ve used the NBM data for Center City Philadelphia to cover the Marathons.

Saturday Forecast

Mostly sunny and a bit chilly and windy. We’ll still be under the influence of a cyclonic flow flow, but the GFS keeps us partly sunny.

11-22-24 18z GFS forecast for Saturday morning. The GFS keep us sunny but a cold windy flow will be noticeable. (Click on image for a larger view.)

Here’s the NBM wind/gust meteogram for Center City Saturday and Sunday—

NBM meteogram for grid point Center City Philadelphia (Click on image for a larger view.)

Sunday Forecast

A warm front will bring some clouds at times during the morning that will break mid afternoon. It will still be somewhat windy.

Here’s the NBM temperature meteogram for grid point Center City—

NBM Temperatures for Center City. (Click on image for a larger view.)