CHANGES IN THE WEEKEND WEATHER Forecast

 

The weather wasn’t quite what had been forecast. The models over-predicted the thickness of the cloud cover today (at times the sun was breaking through mid-afternoon) and were off about the drizzle.

Sat 07:39 PM Update —Today’s models are less impressive with the drizzle for Sunday afternoon. Some are still showing drizzle, mostly mid to late afternoon.
NBM Cloud, rain forecast for 2 PM Saturday. (Clouds are Darker) (Click on image for a larger view.)

Wed 03:56 PM Update — Today’s latest models continue with earlier exit of the rain and the passage of the weak cold front.

Some models have the rain ending as early as noon Thursday. The model blend has the rain ending between 12-2PM. Sunshine breaks out shorty after the rain ends.

A strong cold front moved through on Friday, following the departure of the remnants of what was Hurricane Zeta. Winds have shifted to the NNW and colder air will filter in for Friday night into Saturday.

Cold temperatures at daybreak Saturday. Most areas are forecast to be at or below freezing.

High pressure will be in control on Saturday but will quickly depart Saturday night and a return flow of milder air (and moisture) will move in for Sunday before another cold front moves through Sunday afternoon.

Saturday— High pressure and sunny skies

  • Mostly sunny skies, high to mid level cloudiness moves in during the afternoon, especially western suburbs.
  • Low temperature early morning 44.0º sd 2.6º (NBM model) Blue Bell
  • High temperature 61.6º sd 1.6º (NBM model) Blue Bell.
  • Winds light, NW–>N 5-8 mph

Sunday— A warm front will bring mostly cloudy skies in the morning. A cold front moves through about 4:30 PM preceded by light showers.

  • Low level clouds
  • Some scattered, light drizzle possible, during the mid to late afternoon.
  • Low temperature early morning 39.3º sd 1.6º (NBM model) Blue Bell
  • High temp 52.9º sd 2.4º (NBM model) Blue Bell area.
  • Winds E–>SE 10-12 mph with gusts to 15 mid afternoon.

I’ll update later this evening or Saturday morning

WEEKEND WEATHER OUTLOOK

The stagnant, very mild pattern we’ve been in should continue, as I would describe the current overall situation as a “lack of very cold air” to our north.

Whatever blob of cold air exists in Canada will sag into the western/central US over the next few days, but  our area will still be on the relatively mild side of things. No very cold outbreaks in sight right now, although a weak front will bring in cooler temps for Sunday.

The Short Range Ensemble Forecast Model (SREF) sums it up well with the “540 thickness line”  (RED) staying north of our area—

SREF Model Sunday noon with “540 thickness line” (RED) and other upper air 0ºC lines (magenta, violet)    (Click on image for a larger view.)

Saturday—

As for the specifics for this weekend, a weak cold front will approach on Saturday about noontime, but upper air support is lacking and the front will fizzle out.   Showers with the front far west of the Philadelphia area are expected to reduce to some widely scattered sprinkles.

Speaking of  forecast specifics, it’s been difficult to predict when the low clouds level would lift each morning.  Over the past week, the higher resolution meso-scale models have been a bit too cloudy and the GFS has been useless, as it rarely showed the low clouds and fog that developed each early morning.  Saturday’s forecast is a bit different since clearing skies are expected during the afternoon after the frontal passage according to the model blend.  (Some models have slower clearing through the afternoon. ) Still mild with highs near 73º.

Sunday—

Sunny early.  High pressure moves off to our north and an easterly wind flow will bring in cooler temps and clouds late morning and cloudiness will increase during the afternoon.  Highs only 55º

Fri 03:36 PM Update — latest models have showers early evening Sunday.

Current seasonal average highs are 61º and average lows are 41º.