Philadelphia Weather Outlook

WEATHER OUTLOOK

[su_note note_color=”#d9f2da”]Monday AM Update: The models are showing yet another coastal storm sometime during the Thursday-Friday time frame. Timing issues still exist.

Cold air rushing in after the low departs may again give us the first chance of some mixed non-accumulating precipitation this season. Too many unknowns at this time.  Stay tuned.[/su_note]

The computer model forecasts over the past several days have been very changeable:  While the coastal storm for Monday night into Tuesday is still mostly on-track, the speed of the system has increased while the amount of cold air on the back side of the system has decreased.

We’ll have rain Monday evening into Tuesday morning, heavy at times. No flurries or snow showers expected on Tues night, although things chill down for Wednesday but it won’t be as cold as previously forecast.

Another interesting storm is possible on Thursday morning with the possibility of some frozen precipitation early, before changing to rain.

There’s a lot of uncertainty with this system- there are even large differences even between the GFS and the FV3-GFS!

  • GFS Operational Thursday morning forecast

Next weekend looks to be very cold as a dip in the jet is forecast to be in place.   But things could change.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST- EARLY EDITION

[su_note note_color=”#d9f2da”]Saturday AM Update: Today’s high temperatures will be near their current range (39-41F) and windy. Still unclear how much instability stratocumulus will develop, although the models maintain sunny skies.

Sunday will be more tranquil.

The latest FV3-GFS has brought back the chance of snow flurries (no accumulation) for Tuesday night after the coastal low departs. [/su_note]

A strong cold front will approach Friday afternoon and move through Friday night.  Heavy rain is expected Friday afternoon.

Much colder weather will arrive for the weekend as high pressure builds in on Saturday. However a strong upper cyclonic flow from the departing low pressure system bring windy conditions for Saturday.  Winds 15 mph with gusts to about 30mph are possible.  Temperatures will struggle to reach 40.

With the cold air and cyclonic flow, instability stratocumulus clouds may also develop on Saturday, limiting the sunshine, although the models are down-playing this right now.

For Sunday the winds calm down but still expect unseasonably cold temperatures with highs about 44 with sunny skies.

Looking ahead:

A significant coastal low will develop and approach early Tuesday , giving us another round of windy, rainy conditions for all of Tuesday.  Current track is that we will get heavy rain, but areas in Western PA may receive snow.

The FV3-GFS and NBM were suggesting the possibility of wet snow squalls or flurries moving through with the cold frontal passage Tuesday night, although today’s FV3-GFS has backed away from that.  

Wednesday will be winter-like with very cold temperatures in the 30s!

 

Philadelphia Weather Outlook

ACTIVE WEATHER PATTERN EXPECTED

Thursday Update:  Notice how significantly the predicted jet stream trough for Monday has changed over the past few days:

  • GFS forecast
    GFS Forecast for Monday Morning, Nov 12th

The weekend remains cold, but the temperatures on Monday will be warmer than had been predicted.   Very cold temperatures are now forecast for Tuesday night into Wednesday.

[su_note note_color=”#d9f2da”]The current outlook for this weekend is dry, windy and chilly on Saturday and mostly sunny and chilly on Sunday. [/su_note]

My post last Sunday identified the cold outbreak that’s expected this weekend. With the amplification of the jet stream and the development of a significant trough by next Tuesday, a coastal system is expected to develop and to bring rain to our area, and some snowfall is possible in western PA.

Even more interesting is that the FV3-GFS (still under development but expected to become the NWS main global model in January) suggests that even some wet snow flakes may move in  during the end of the storm Tuesday night.

This outbreak of cold weather will be the first of several, with a number of storms expected between now and Thanksgiving.   Stay tuned.

Weather… and Other Things 'Up in the Air'