Category Archives: Philadelphia Weather Outlook

FRIDAY AND WEEKEND OUTLOOK

Update Fri 12/30 @ 9:36 AM — A quick update to the weekend outlook posted last night (below), based on the latest models.

Saturday will be quite cloudy. Some fog possible in the morning with low clouds throughout the day.

Some light showers are possible late morning and around noon especially just over the river in NJ. The bulk of the rain will be moving in between 2 and 5 PM around the city. Rain tapers off after midnight. Bulk of the rain is moving to our southeast and total rainfall will be less than 0.4 inches in or area.

NBM is showing a slight decrease in mean high temperature on Saturday to about 53º but it has increased its spread to 3.5º (So think of it as 53º ± 3.5º, a wider than usual range of uncertainty.)

For Sunday, New Year’s Day, skies clear during the morning hours. Winds and wind gusts still robust, but maxing out about 27-30 mph instead of the 35 mph gusts posted yesterday. NBM mean high temperature of 53º again with an even larger range of uncertainty, ± 4.0º.

I’ll update the forecast later today.


Previously Posted Thu 7:49 PM —

If you’re planning on outdoor activities, Friday will likely be the best day weather-wise of the coming three.

Friday

Sunshine with milder temperatures for Friday, with a high of 54º-55º. Thickening high level cirrus clouds expected mid to late afternoon.

NBM model forecast high temperatures for Friday. Black contours are 2º increments (Click on image for a larger view.)

Saturday and Sunday Outlook

Saturday will be cloudy. Scattered light sprinkles as early as noontime, but steadier rain moves in between 2 and 4 PM. It will be mild. Latest models have backed off on forecasting the heavy rain; light to moderate rain expected around midnight.

Sunday will continue mild and the sun should break out as skies clear. A big consideration will be the wind, with wind gusts around 30-35 mph, tapering later in the afternoon.

Thursday’s 19z NBM model wind meteogram for Blue Bell PA (Click on image for a larger view.)



THIS WEEK’S WEATHER

How much rain did we get?

It’s still raining in many places at 10 AM and the rain is expected to end around noon. Cloudiness should diminish from south to north about 2-4 PM.

How much rain did we get?

MRMS rainfall estimates through 9 AM Friday. (add another 0.10 inches through noontime) The numbered contours are in mm. 25.4 mm =1 inch. (Click on image for a larger view.)

Thursday Weather Update

Update Thu 12/15 @ 1:08 PM — A changeover to all rain in the Philadelphia area. Heaviest rain between 6 PM and 11 PM. Total rainfall about 1.2″ to 1.7″

Highest wind gusts this evening towards midnight—

NBM wind meteogram for Blue Bell, PA . Highest wind gusts around midnight. (Click on image for a larger view.)

Following this storm, we’ll be going into a generally colder pattern for the week before Christmas. A snow storm is currently being forecast by the GFS, GEFS and ECMWF for Friday Dec 23rd. I’ll keep tabs on it.


My 2022-2023 Winter Climate Snow Outlook

Thu 12/15@ 7:36 AM — Forecast Review

We’re getting more sleet than I had forecast; (“perhaps some sleet mixed with rain initially”) the delay of the precip as forecast by last night’s HRRR and NBM was wrong.

Temperatures in my neck of the woods are already above freezing (33º-34º) but a thin layer of colder air at about 2000-3000 feet is giving us the sleet. This layer may persist a bit longer as some dynamic cooling occurs, but a changeover to rain should occur about 9 AM.

With the sleet coming down, this morning’s HREF is showing it should be freezing rain rather than sleet, clearly not correct either.


Little Wintry Mix in Philadelphia & near Suburbs

Update Wed 12/14 @ 8:50 PM — A further review of the latest Canadian HRDPS and German ICON models as well as this afternoon’s ECMWF show a delayed onset of the precip here allowing temperatures to rise at critical levels of the atmosphere.

These models are in support of the preferred HRRR forecast—Little in the way of wintry mix (perhaps some sleet mixed with rain initially) except in areas of western Chester County and north into Lehigh County which may have more sleet/freezing rain before change to rain.

The models show very light precip moving in between 8 and 10 AM, with temps above freezing at critical vertical levels.

Tonight’s 00z NBM model captures this well at 9 AM; most of the precip is still south of the city with temps too warm for wintry precip here—

Tonight’s 00z NBM shows critical temperatures north of the precipitation at 9 AM. The precip has barely entered Philadelphia. Bourgouin negative energy contour is a measure of the likelihood of sleet. West and north of this contour are the areas which most likely to have sleet. It all changes rapidly to rain by late morning. Notice how far north the 32º line (white) is. (Click on image for a larger view.)


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