Category Archives: Philadelphia Area Weather Forecasts

THIS WEEK’S WEATHER

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Friday Forecast

Update Fri 03/03 @ 3:32 PM — Like earlier this week, evaporative cooling at the onset of the rain has resulted in a mix of rain and wet snow this afternoon. (Temperatures are in the low 40s) I went back to look at this morning’s models. The GFS and HIRESW-FV3 showed this possibility. The NAM and HRRR did not.


Update Fri 3/03 8:42 AM — The trend continues for a later start of the rain. Now, most likely 3-4 PM, but earlier far southwest of the city. Rainfall during the afternoon hours will be very light, only about 0.03”. Heavier rain starts about 9 -10 PM.


Update Thu 03/02 @ 5:25 PM — The trend for the large rain storm that will affect us Friday has been for the rain to start later in the day. This trend has continued with this afternoon’s models.

Current forecast: Rain moves in between 1 and 3 PM, earlier in the far southwestern suburbs of Philadelphia. It will become quite WINDY, especially towards midnight Friday.

By Saturday morning, about 0.75″ to 1.3″ of rain is expected in our immediate area—

Today’s NAM-NEST Total rainfall by 11 AM Saturday. Model precipitation forecasts should never be taken literally regarding placement of the heaviest rain bands. (Click on image for a larger view.)

Skies remain cloudy and unsettled on Saturday with lingering rain sprinkles and snow showers far north. It will be windy.


Thursday Update

Update Thu 03/02 @ 8:57 AM — As we saw yesterday, cloud cover is one of the toughest weather parameters to forecast correctly. Today may be no exception.

Most models have clouds lifting to significant high-level cloudiness with sun filtering through by noon Thursday. But the GFS has some stubborn mid-level cloudiness lingering into mid afternoon.

As for the rain on Friday, the trend has been for a later onset, probably closer to 1-2 PM. The rain moves in from the south. The rainfall later Friday and Friday night will be heavy at times. About 1-1.5″ of rain expected.

As mentioned in last night’s update, Saturday looks to be very cloudy with light widely scattered sprinkles and even some snow flurries (northern sections) possible.


Update Wed 03/01 @ 8:09 PM — A fast moving system will bring light showers just before daybreak Thursday. Showers move off to the east by 8 AM and clouds break for sunshine through a high cloud layer by about 11 AM from west to east.

The larger storm to affect our weather on Friday looks like it will move in later in the morning. around noontime. The chances of any sleet or frozen precipitation at the start looks to be low. A rain event for our immediate area.

Rain Friday afternoon and night.

Saturday looks very cloudy with low pressure lingering. Even a chance of widely scattered snow flurries or sprinkles.

Wed 8:16 PM Forecast Review — We had significantly more cloudiness today than forecast.

Wednesday Through Friday

Previously Posted Tue 8:15 PM —

Low pressure system that lingered (as forecast) today will move off to the east. Wednesday will be mostly sunny. Highs 52º-53º. Winds increase somewhat in the afternoon.

GEFS forecast for Wednesday at 1 PM Low pressure (1) links up with a stronger low in the Great Lakes to develop into a coastal low (2) near New England on Thursday. (Click on image for a larger view.)

For Thursday, low pressure approaches from the west, but the models have it transferring its energy to a secondary low off the New England coast.

We start out cloudy on Thursday with some showers mostly western suburbs. Then partly cloudy/partly sunny. Mild. High near 60º.

On Friday, a strong storm (similar to Monday night’s storm) approaches and takes a western track. We’ll be in the warm sector, but precip may start out as sleet/snow mix in the early morning. Rain for much of the day.

GEFS forecast for Friday 1 PM. (Click on image for a larger view.)



WEEKEND WEATHER FORECAST

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Updated Sunday Forecast

Update Sat 02/25 @ 10:06 PM —Some early morning sunshine will fade behind some low cloudiness in the mid to late morning as a weak front approaches from the west.

Clouds break for sunshine in the early afternoon, but it will become quite windy, with gusts in the 30 mph range. High 53º, almost 20º warmer than today.

Sat 10:00 PM Forecast Review — Despite the outlier NAM forecast, we only had what was an hour or two of snow flurries. No accumulation. I think we still qualify as having had a snow-less winter so far.

Update Sat 02/25 @ 10:35 AM — The morning models (12z model runs for EST ) become available between 8:15 AM and 11 AM. Accumulating snow is conspicuously missing. A model spin-up issue or our snow-less winter continues?


Update Sat 02/25 @ 9:12 AM — In a way, I’ve enjoyed this mild, snow-less winter.

But back last fall, I was spending considerable time improving the appearance of my model snow graphics in preparation of this winter. So far this winter, I haven’t had a chance to use these graphics and I must confess that today’s light snow showers are a thinly veiled attempt to put them into action.

Today we’re expecting to see some snow showers develop as low pressure moves both to our north and south.

The highest resolution models (2-4 km resolution) show virtually nothing accumulating, but the lower resolution models (13km NAM, and 10km Canadian RGEM) do show some snow accumulation, a coating to 1/2 inch in some locations.

Here’s current radar with superimposed RAP model graphics —

Radar at 9:25 AM with moisture convergence (blue contours) and Omega (vertical velocity yellow contours) Snow showers helped by some vertical motion and convergence ahead. (Click on image for a larger view.)

Here’s the latest NAM model snow accumulation, just became available—

Today’s 12z NAM snow accumulation forecast

Previously Posted Fri 6:00 PM —

Low pressure will move east and will be south of us as some moisture just brushes the Philadelphia area Saturday afternoon. The NAM, as mentioned in my earlier post had forecast a very light accumulation for us, but it appears that any light accumulation will be closer to the Delaware border and into South Jersey.

Saturday

It will be cloudy and cold Saturday with some snow flurries just reaching north of the city during the early to mid afternoon. To our south, near the Delaware border and into South Jersey, there’s a chance of a coating, up to 1/2 inch.

This simulated radar forecast from the NAM captures the extent of the northern extent of the flurries and also shows where a coating is more likely. This afternoon’s GFS has a fairly similar forecast—

Today’s 18z NAM simulated radar at 4 PM Saturday.

This is the current NAM forecast for snow accumulation. It is likely over-forecasting snow accumulation—

High temperature only 34.0º sd 1.9º ( NBM model- location Blue Bell, PA)

Sunday

High pressure builds in and some early cloudiness lifts in the mid morning for sunshine for the rest of the day. Much milder but WINDY.

High temperature 50.0º sd 1.7º ( NBM model location Blue Bell, PA)

Winds

NBM meteogram for Wings Field, Blue Bell PA