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Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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Thursday Forecast Update

Posted Thursday 12/05/24 @ 8:44 AM — There are showers/snow showers to our west that will likely move just north and just south of Philadelphia this morning, perhaps grazing us.

Current Radar with superimposed MRSMS radar, Omega (vertical motion -yellow contours) and wind streamlines (green) at 10,000 feet. Arrows show likely path of the main showers, but additional showers/snow showers may break out dynamically. (Click on image for a larger view.)

As for the winds, they will be here, as forecast by mid to late morning. Latest RTMA (real time mesoscale analysis) at 8:15 AM shows the higher wind gusts are moving towards us from central PA

Current wind gust onditions based on the RTMA This area of high winds will be here shortly. (Click on image for a larger view.)
Quick Update

Posted Wednesday 12/04/24 @ 11:30 PM — With the critical upper air temperatures all below freezing, I think the models are showing too much rain and not enough wet snow here. While little or no accumulation is still expected, more of the squall showers will have wet snow flakes instead of rain drops, even near the city.

Tonight’s GFS shows critical level temperatures all below freezing here. Only near ground temperatures are in the upper 30s
Thursday Forecast Update

Posted Wednesday 12/04/24 @ 7:30 PM — There has been little change in the forecast for Thursday. Some rain showers this evening will move out later.

The strong cold front moves through Philadelphia about 6 AM accompanied by light scattered rain showers with some scattered snow showers/squalls to our northwest. Wind gusts near 40 mph will increase to near 50 mph towards noon.

12-04-24 18z GFS forecast for 7 AM Thursday. Green = rain Violet = snow. showers The purple line is the 32º isotherm at 900 mb (about 3000 feet) Near ground temperatures will be well above freezing. (Click on image for a larger view.)

Temperatures drop in the afternoon to below 32º by late afternoon.

Wednesday into Thursday: Active Weather

Posted Tuesday 12/03/24 @ 4:32 PM — An approaching warm front on Wednesday will bring windy conditions and perhaps some shower activity in parts of the Philadelphia area Wednesday evening.

Cold air is plunging towards us with the cold front expected to move through about 5-7 AM Thursday with showers and increasingly windy conditions.

Tuesday afternoon’s 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. Cold air rushing towards us. (Click on image for a larger view.)

Winds increase significantly after the frontal passage as temperatures drop. Additional rain showers and even some snow squalls possible with gusty winds in the 40-50 mph range Thursday late morning through much of the afternoon.

Total precipitation should be very light, in the range of 0.05″ rain or snow water equivalent.

Cold and unsettled for Friday.

Strong Cold Front Thursday Morning

Posted Tuesday 12/03/24 @ 10:24 AM —Windy conditions and periods of sun and clouds expected for Wednesday. Increasingly cloudy later in the day.

An arctic cold front will move through Thursday morning. The big feature will be the high wind gusts, over 40 mph and the rapid drop in temperatures behind the front. Snow squalls (minimal to no accumulation) may occur a few hours after the frontal passage.

Latest RRFS forecast for 7 AM Thursday morning. Some showers, possibly with some snow flakes and wind gusts (contours) with this frontal passage. Higher winds develop later in the morning with possible snow squall.

The front appears to come through with two punches. The actual front (wind shift/pressure change) occurs about 5 AM to 7 AM. Rain showers, possibly with some snow flakes, accompanies the actual front along with gusty winds.

Another gust front develops and moves through later in the morning, around 11 AM. High wind gusts near 45 mph and some snow showers possible. Again, little to no accumulation

Rapidly declining temperatures during the afternoon, reaching below freezing by 3-4 PM.

The weekend looks cold.

Originally Posted Sun 4:36 PM —For several days, the radio and TV forecasters are talking about “SNOW” for late Wednesday into Thursday. My personal feeling is that after months of sunny skies and no rain, they’re starved for attention. As of this afternoon, I don’t see any snow in any of the models deserving this sort of advance mention. (The word “HYPE” does comes to mind.)

Since last Friday, the models have been hinting at the possibility of very light snow flurries or snow flakes mixed with rain late Wednesday evening into into the predawn hours of Thursday. No accumulating snow.

The truth is, the reinforcing cold front responsible for this “snow” is moisture deficient and over the past several days, the models have shown no tendency for any surface low pressure formation. All models show temperatures above 32º here Wednesday night into Thursday and even above the critical snow temperature of 36.5º

Only one model, the German ICON-EPS (ensemble model), shows any accumulation and that amount is less than 0.10 inches of snow (a coating at most). Even the ICON-EPS has temperatures above freezing here—

12z ICON EPS accumulated snow at 1 AM Thursday. (Click on image for a larger view.)

We may see some snow showers, lake effect snow that moves from the northwestern PA into our area early Friday morning. Again not worth talking about “SNOW!” in advance for this sort of weather event.

Check back for updates tomorrow

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Week Outlook Early Edition. Snow??

Posted Sunday 12/01/24 @ 9:21 AM — First, today’s morning clouds were predicted and but the latest models have these clouds hanging tight for most of our area through 4-5PM, instead of dissipating earlier. (Far northern areas may see some sun by afternoon.)

As for this week, all the radio and TV forecasters are using the word “SNOW” for late Wednesday into Thursday. My personal feeling is that after months of sunny skies and no rain, they’re starved for attention. I don’t see much in the way of any meaningful snow deserving this sort of hype.

Since last Friday, the models have been hinting at some snow late Wednesday into late Wednesday night. The truth is, the reinforcing cold front responsible for this “snow” is moisture starved and over the past several days, the models have shown very little to suggest that we’ll get anything more than snow showers. Right now, I see only snow showers that may give a coating in most areas. I don’t see the need for snow shovels. Perhaps an ice scrapper for your car Thursday morning to remove frozen melted snow from your car windows.

The latest GFS and the caption below explains the situation—

12-01-24 06z GFS. for 7 AM Thursday. White line is surface 32º Light blue line is surface 36.5º, the approximate minimum temperature for snow. Basically it’s too warm in the lower levels of the atmspherre for snow to accumulate. The upper level critical temperatures for snow (lavender) , 500-1000mb thickness (red) and ( magenta) support snow formation, snow will melt on the way down. The blue tint among the green precipitation field is where the GFS predicts snow falling, mostly north of the 36.5º line. (Click on image for a larger view.)

I’ve been keeping an eye on this situation, but, if your’e hoping for real snow, you’re likely going to be disappointed.

Originally Posted Fri 6:34 PM —We had the instability showers/snow showers today as forecast yesterday by the RRFS and GFS. Those will be ending with sunset, as cold air streams in from the northwest.

A broad dip in the jet flow will cause cold weather to be with us through the weekend and into much of the next week.

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 Composite RADAR. (Click on image for a larger view.)

For Saturday, cold with instability cloudiness again about noon into early afternoon. No showers expected. Sunday continues sunny and cold.

Saturday Forecast

Sunny in the morning, instability cloudiness towards noon into the early afternoon, then skies clear. Windy during the mid-day hours. Temperatures in meteogram below. Wind chills (‘apparent temperatures’ in the meteogram) below 30º

Sunday Forecast

Some warm air aloft from a southwesterly wind will cause some cloudiness during the morning hours, then partly sunny. Still somewhat windy mid-day into early afternoon.

A weak cold front moves through Sunday evening dropping temperatures.

NBM forecast temperatures for Blue Bell, PA (Click on image for a larger view.)
Looking Ahead

A cold front with a possible interaction with some southern jet stream energy will bring some very light showers or showers with some snow flakes later Wednesday. There’s uncertainty with is system.