Category Archives: Philadelphia Weather Outlook

WEEKEND WEATHER OUTLOOK

A somewhat uncertain forecast for Saturday with a likely fine weather day on Sunday.

A dip in the jet stream in the central US will cause a front to move through sometime in the Friday to Saturday time frame.  There’s uncertainty with the timing of the frontal passage. Several models show different timing and differ in developing waves of low pressure along the front Friday into Saturday.

Rain likely Friday morning and Friday night into Saturday morning.  It’s unclear if the waves of low pressure will move off the coast to allow clearing Saturday afternoon.

High pressure builds in for Sunday.  Cooler on Saturday and Sunday.

I’ll update on Friday.

WEEKEND FORECAST UPDATE – THURS

[su_box title=”Forecast Update Fri 8 AM” box_color=”#defcdc” title_color=”#000000″]The forecast is on track for the rain to taper and end mid to late morning on Saturday. Low level clouds remain with a chance of a light, brief sprinkle or two in the afternoon with winds shifting from easterly to west-southwesterly in the mid afternoon.

Additional Update Fri 11 AM: This morning’s NAM has the heavy rain ending by 8 AM Saturday, but continues with very low clouds and light intermittent showers for the remainder of the daytime Saturday.  The NAM and National Blend of Models crank out 0.03 inches water in the late morning and 0.07 inches of water in the afternoon. Comparing the two maps in this post, you can see that the trend has been for the system to move more slowly again.

NAM forecast
NAM forecast for Saturday afternoon

Sunday still looks to be dry. [/su_box]

Things continue to change with the forecast for this weekend.  The latest GFS model shows the coastal low pressure system moving reasonably quickly, a marked change from what the models were showing just a few days ago.  

FV3 GFS
FV3 GFS Forecast for Saturday afternoon

It appears that the rain will begin early Friday evening with the heaviest rain Friday night, ending sometime Saturday late morning.

Low clouds are expected to linger through Saturday and considerable cloudiness is expected on Sunday before the second system arrives for Monday.   Sunday will be unsettled but dry.

As good as the models are, it’s remarkable how much a forecast can change in a matter of days. Something to remember when advance forecasts for large snowstorms end up being a bust.

I’ll update the forecast Friday evening.

WEEKEND WEATHER OUTLOOK- UPDATE

[su_box title=”Forecast Update Thursday AM” box_color=”#defcdc” title_color=”#000000″]The latest models show a change in the forecast. The coastal low gives us rain for Saturday, but departs much more quickly now. Sunday will be windy and chillly but not rainy. The second low moves in on Monday.[/su_box]

The latest models show a coastal low bringing us rain on Saturday as an upper low to the west along with another low in the Midwest causes the coastal low to linger over our area into early Sunday.  The phasing that was considered a possibility to create a superstorm is no longer being depicted.

So, not the best weekend, weather-wise, as rain is likely for Saturday and early Sunday morning. Much of Sunday will be unsettled, cloudy and windy.

I’ll update on Friday.