Category Archives: Philadelphia Area Weather Forecasts

Philadelphia Area Weather Forecasts

THIS WEEK’S WEATHER

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Update Sun 2/19 8:40 AM — As alluded to last night, the model cloud algorithms predicted cloudiness for today, but the vertical relative humidity field values were not all that high, so I was curious about how much cloudiness we would actually see today. So far, not much. While a few periods of cloudiness are still possible, I don’t think it will be as cloudy as the radio forecasts are suggesting.

Previously Posted Sat 8:45 PM —

Some Cloudiness Sunday… Watching next Saturday

Today’s models continue with a forecast of considerable mid-level cloudiness during the day Sunday. This sort of cloudiness can be the sort that lets dim sunlight through. The models also show some areas where there will be intermittent clear skies.

The cloudiness forecast is the result of several weak upper air disturbances moving through.

I’m sort of curious how much cloudiness we actually get, since the relative humidity vertical profiles are not that impressive. I guess we’ll see. High temperatures around 53º (Blue Bell). It will become fairly windy during the afternoon and evening.

Watching Next Saturday

There seems to be usually high agreement with today’s global models (GFS, GEFS, ECMWF, ICON, GEPS, NAEFS) that a ‘cold air damming’ setup will develop early next Saturday as warm air rides over cold air at the surface. This is a snow –> sleet–> rain scenario for the immediate PHL area. An inch or so of actual snow is possible, as currently forecast, but it will all be washed away by rain later in the day. Temperatures rise the next day.

This is the most substantial setup for a bit of snow that I’ve seen this entire winter. Many lesser possibilities have faded into oblivion this winter. (This setup was originally forecast by some models to occur this coming Thursday, but that faded away.)

We must not forget that this is about 7 days away. In the weather world, that’s considerable forecast lead time. Much can change in that time frame. Stay tuned.

NAEFS forecast for nest Saturday at 10 AM. Critical temperatures contours (red, white, violet, blue, light blue) are all supporting snow at the onset. But temperatures expected to warm up as the day progresses. (Click on image for a larger view.)
Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#weather #paweather #wx #pawx #philadelphia

Current and Future Overview

The cold front has taken its time moving off the coast, although last night’s models had the sun not breaking through until “mid to late afternoon”. Current radar suggests precip is lingering.

The current weather map (NAEFS) shows the jet stream winds moving up from the south while high pressure over the Great Lakes moves in from the west.

NAEFS forecast for today. Jet Stream Winds, Surface Pressure and 540 thickness line. (Click on image for a larger view.)

This jet stream pattern will transition to a flat (“zonal”) flow by Wednesday—

NAEFS statistical mode forecast for Wednesday. The red 540 thickness line captures the flatness of the jet flow. The model suggest a fair amount of interaction between moisture (warm) from the south and and colder high pressure to the north, with possible wave formation. This could set up an active weather pattern. Some mixed precipitation possible at some point late in the week, depending upon how things play out.

Saturday

High pressure builds in from the west but will move off to the east by Saturday night.

Sunny and seasonably cold. Still breezy, winds increase during the afternoon.

High temperature 43.5º sd 2.0º ( NBM model location – Blue Bell, PA)

Sunday

As high pressure moves off, moisture returns aloft and a significant amount of mid-level cloudiness is expected.

High temperature 51.1º sd 1.9º ( NBM model location- Blue Bell, PA)

NBM Wind Meteogram for Blue Bell PA (Click on image for a larger view.)

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#weather #paweather #wx #pawx #philadelphia

Back where we started

Update Sun 2/12 10:53 AM — This morning’s NAM has reverted back to the rain moving into Philadelphia. Now about 8-10 PM and continuing into the night. The Eagles win forecast hasn’t changed.

Forecast change

Update Sat 2/11 10:22 PM — Tonight’s high resolution models (NAM) keep the rain well south of our area Sunday evening. A significant change in the forecast.
Update Sat 2/11 11:18 PM — BTW, the GFS and tonight’s Canadian RGEM still have the rain here, as previously forecast. My bet is on the NAM and the Eagles.

Update Sat 02/11 @ 5:56 PM — No major changes in the forecast for Sunday. Rain moves in from the south between 4-6 PM. In the city, it will be very light and there will be a sharp cutoff just north of the city’s northern immediate suburbs. This has been a boundary or edge condition for the precipitation shield for days and some models are further north, some are further south.

The HREF forecast provides a good compromise—

18 z HREF simulated radar with accumulated precip contours (light green) . Total amounts range from 0.02” to as much as 0.10” in the immediate PHL area, more south, less north. Click on image for larger view

One change is the precip moves out as early as 11 PM to midnight, just in time for the Eagles victory celebration.

Still no signs of any snow here for the next 10 days!

Update Fri 2/10 10:43 PM — Tonight’s models are trending towards a bit earlier start of the rain on Sunday in Philadelphia, perhaps as early as 4-6 PM. Unfortunately, it appears that it might advance further north with somewhat heavier rain making it into the city than previously forecast. Stay tuned.

A secondary cold front will pass through Friday night and Saturday will be much colder than previous days.

A coastal storm with a closed low will be blocked from moving north. The precipitation shield will affect NJ and Delaware during the day Sunday. Light showers will move in to the immediate Philadelphia area Sunday about 5-7 PM

Saturday

High pressure will bring mostly sunny skies. Windy conditions in the morning will gradually subside during the afternoon. Some clouds towards sunset.

High temperature 45.1º sd 1.5º ( NBM model- location Blue Bell, PA)

Sunday

The coastal low will move north but be blocked by high pressure. While the rain will be significant in South Jersey and Delaware, only light rain is expected to move into Philadelphia early evening.

Here’s the northern-most extent of the rain by 7 PM, according to the high resolution NAM-NEST —

Today’s 18z NAM-NEST simulated radar forecast for 7 PM Sunday. The NAM-NEST forecast is very similar to several other models, perhaps just a bit further north with the rain than several.

High temperature 45.6º sd 2.5º ( NBM model – location Blue Bell, PA)