Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Update Sat 3/11 8:54 PM — Sunday’s forecast below is unchanged. High temp 46.5° sd 1.4°

Update Sat 03/11 @ 10:08 AM — We had the wet snow here before 8AM. The balance of precip will be light rain. There’s a wide range of model opinion regarding clearing today.

After reviewing the models, it appears that a considerable amount of low cloudiness will remain, but there’s a chance of some short-lived breaks of sun in some areas this afternoon. Some additional showers possible.

The HRRR shows another band of light showers moving through about 3-5 PM or so—

This morning’s 12z HRRR shows clouds (black/grey) and showers at 4 PM today. (Click on image for a larger view.)

That area is visible on this morning’s hybrid radar—

This morning’s Hybrid Radar with RAP model Omega overlay. Light showers may rotate through about 3 PM (Click on image for a larger view.)

Update Fri 3/10 11:02 PM — Tonight’s models continue to show non-accumulating wet snow showers, from the just outside of the city and north and west, Saturday morning.

Previously Posted Fri 4:51 PM —

This weekend will mark the transition into a different weather pattern than we’ve seen in awhile. Two low pressure systems will move in and develop – one Friday into Saturday and another late Sunday into Monday. These systems will pull cold air down from Canada and the jet stream pattern will become cyclonic and somewhat amplified along the Eastern US.

This translates into below average temperatures, windy and quite unsettled conditions, starting today (Friday) and into much of next week.

Saturday

Low pressure that brought rain Friday night will blossom in the western Atlantic. Upper level low pressure will merge with this storm. Wrap around moisture from this surface low will bring continued cloudy conditions and showers/snow showers on Saturday morning. It will be windy and cold. Some widely scattered showers may linger into the afternoon.

Here’s the GFS for Saturday—

GFS model forecast for Saturday 1 PM. Wrap around moisture from low pressure in the Atlantic will bring rain and snow showers. (Click on image for a larger view.)

Despite temperatures well above freezing, snow showers are expected to develop in some areas. It would not surprise me if the snow shower coverage is greater than predicted below—

NAM-NEST forecast Precipitation Type for 11AM Saturday. Blue: snow showers (Click on image for a larger view.)

High temperature 45.7º sd 1.5º ( NBM model location Blue Bell, PA)

Sunday

Another low pressure system approaches during the day. Sunday starts sunny through increasing high cloudiness.

Thickening and lowering cloudiness in the afternoon.

Some precip moves in during Sunday evening, which most likely will be rain in most areas.

GFS forecast for Sunday at 7 PM. Low pressure moving in from the west and south. (Click on image for a larger view.)

High temperature 46.9º sd 1.5º ( NBM model location Blue Bell, PA)

Winds

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

For next week, very deep low pressure develops near Cape Cod. We’ll be affected by windy conditions and cold temperatures.

GFS for Tuesday shows deep upper and surface low pressure systems—

GFS forecast Tuesday. Windy cold and unsettled here. (Click on image for a larger view.)
ECMWF 300 mb wind forecast (with red 500-1000 540 thickness) for Tuesday night shows broad but deep upper air trough in the East with closed low over the Northeast. (Click on image for a larger view.)

Daylight Saving Time and Weather Forecasts

Sunday morning is the beginning of Daylight Saving Time.  I love the extra daylight at the end of the day, but for  “weather nerds”, Daylight Saving Time means the models come out an hour later.  For those of us on Eastern Time, the evening models become available inconveniently late for the next day’s forecasts!

I’ve written extensively about this in past years—

Little Known Facts about Daylight Saving Time and TV Weather Forecasts

Daylight Saving Time and Weather Models

“Check Back at 11” — TV Weather and Daylight Saving Time