Philly Weekend Weekend Weather Update

Advancing moisture aloft with cirrocumulus undulatus
Advancing moisture aloft with cirrocumulus undulatus

Latest NAM and GFS models similar in having the remnants of what was tropical storm Bill move directly over our area for Saturday night into Sunday morning.  Both models crank out about 2 inches of rain with the heavy rain falling after midnight Saturday into daybreak Sunday.

It’s not surprising that the NWS issued a flash flood watch for this time period.

It appears that Saturday will start dry, but showers and thunderstorms develop late afternoon and become progressively heavier during Saturday night.

See my earlier forecast for other details.

Philly Weekend Weather Outlook

Those of you following the past days forecast details would notice that the model forecast accuracy has not been at its best– the position and movement of the warm front has been difficult to accurately predict.

It appears that the warm front has finally moved past our area Friday morning (winds have shifted to the southwest).   There’s the possibility of some thinning cloudiness during the afternoon and maybe some breaks of sunshine.

In fact, the “maybe some breaks of sunshine” may be the forecast challenge for this weekend.

This weekend, we will be in a south to southwesterly flow of very moist and somewhat unstable air.  The models are predicting heavy rain for Saturday night and early Sunday morning.  Maybe you can hang your hat on this, maybe you can’t.

But if we assume that late Saturday afternoon into early Sunday morning will be a definite rain time frame, the rest of the weekend weather forecast is a bit more challenging.   Forecast uncertainty is high this weekend regarding details.

For Saturday, we’ll start with some clouds, maybe some breaks of sunshine, warm and humid.  High 84.  Showers and possibly some thunderstorms develop mid to late Saturday afternoon into the evening.  Rain may be heavy.

Sunday starts with lingering rain and showers, then it ends.  Thinning clouds possible in the afternoon and maybe some breaks of sunshine in the later afternoon.    High 83.

I’ll try to fine tune this during the weekend.

 

Philly Weekend Weather Forecast

There’s been a forecast change with the weather models– the cold front that had been expected to move through Saturday with showers and thunderstorms is now expected to dissipate with most of the dynamics remaining far north and west.

So Saturday is now looking dry with considerable cloudiness and breaks of sunshine.  High 89

With surface winds changing to the north,  somewhat less humid weather for Sunday, with partly sunny skies .

 

 

 

Storm Forecasts & Other Things "up in the air".