Some interesting observations about upcoming weather for the Philadelphia area—

  • The rain now expected Thursday into Friday morning was not really picked up by the models until two days ago.  The exception was the new FV3-GFS, which predicted the coastal storm almost two days before the other models jumped on board.  (The ‘exclusive forecast’ from one of the TV stations was predicting a full week of dry weather just last weekend.)
  • This upcoming weekend, especially Friday through Saturday, will be anything but Spring-like.  Windy conditions and unseasonably cold temperatures are expected, especially on Saturday.
  • The FV3-GFS is predicting a very cold outbreak Monday night into Wednesday next week.  Included is a possible changeover from rain to snow late Monday into Monday evening.  Maybe an outlier of a forecast, but something to watch, considering the model’s success this week.


Update Saturday morning. The short range models show signficantly less stratocumulus cloudiness than the NAM. I guess we’ll see.

Following a cold front Friday evening, high pressure will build in for Saturday and Sunday.

After today’s very warm temperatures, Saturday and Sunday will be much chillier.  Winds and some clouds on Saturday will make the day feel even colder.

Saturday will start sunny, but cold air aloft will result in a considerable amount of instability stratocumulus cloudiness at times, especially late morning and early afternoon.    It will be windy and gusty. High 46-48.

Stratocumulus cloud overage expected for Saturday (NAM NEST) (darker shades–> more clouds)

Sunday will be sunny with light winds.  Temperatures will still be below average, with a high of 45.

Average high temps are about 54ºF for Philadelphia.


Whoops….we may need to cancel those sunny breaks I forecast within the past hour. I took a look at the very low level cloud deck and it hangs firm until very late.

Very low level clouds

The latest GFS has some breaks of sun coming in sometime between 1 and 5 PM due to a dry slot from the south.High temperatures are also coming in much lower than predicted-

Revised High Temps

High temps in the 53-55 range, occurring later in the afternoon:

Orange low to mid 50s.


My post from last year about Daylight Saving Time and the forecasts you see on the 10 and 11 PM TV news is useful information to check out.

The short version is that the latest runs of the GFS and other global models are not completed nor available in time for the late night TV weather segments when we switch to Daylight Saving Time on the east coast.

Indeed, the first “products” of the GFS model first become available about 11:32 EDT.

With the exception of the NAM, the forecasts you see on the 10PM or 11PM (east coast)  news/weather can only be based on older model runs from the short range models and [possibly] the newest NAM.   Indeed, some of the short range models at those times are, in turn,  “initialized” from the earlier afternoon NAM model, not necessarily the latest!