THANKSGIVING ForEcast UPDATE

Thu 09:15 AM Update —  The latest HIREF (High Resolution Ensemble Forecast- pre-release version) cloud cover forecast for 1 PM Thursday—

HIREF-EXP3 (pre-release) cloud forecast  (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.

from Tuesday…

Tonight’s models just becoming available show the front moving through 6-8 hours earlier in the day Thursday than previously forecast. Showers end early afternoon followed by some clearing by mid afternoon.

THURSDAY-THANKSGIVING FORECAST

I’ve been following the model forecasts for the Thanksgiving holiday and a high consensus has developed regarding the weather on Thursday.

Low pressure in the Ohio valley will pass to our west as a warm front associated with the low moves through very early Thursday morning. It will become mild!

After some moderate rain very early morning, there may be a break in the action before additional showers develop during the day as a result of an upper air wave passing over us—

Upper air wave (blue arrow) causing showers during the day Thursday before a weak cold front moves through.

(A few days ago, it seemed that skies would clear Thursday morning, but it now appears this upper air wave will result in mostly cloudy skies with intermittent showers through the day before a weak cold front moves through during the evening.)

Thursday—

  • Cloudy with light showers possible through the afternoon.
  • Low temperature early morning 42.8º sd 2.5º (NBM model) Blue Bell
  • Mild. High temp 59.7º sd 2.0º (NBM model) Blue Bell area.
  • Winds SW–>WNW 12 mph.

A weak cold front moves through during the evening hours.

There’s still a “relative lack of very cold air” to our north, as mentioned a couple of weeks ago. Some of the models are showing a deep dive of some cold air in Canada early next week which would shift our temperatures from above average to below or closer to average.

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.

A series of weak frontal systems will pass through our area over the weekend. The general overview is that Saturday will be the nicer of the two days this weekend.

The latest GFS model shows some cloudiness moving in from the west Saturday afternoon. (Previous model runs had kept us sunny.) There’s uncertainty about light drizzle Sunday afternoon but the trend is towards some light scattered drizzle mid to late afternoon.

Saturday—

A weak cold front moves through before daybreak Saturday. A northwesterly flow of air moves in, but temperatures will be above seasonal averages. (average high 51º-52º)

  • 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—

As the high pressure system moves to our north, an easterly to northeasterly flow will develop for Sunday and significant cloudiness will develop.

Low pressure to our west will slide off to our northwest and a warm front will move through late Sunday and then a cold front Sunday night. Some, but not all models, are showing light showers and drizzle mid to late Sunday afternoon. It will be a stereotypical dark, cloudy November day although still mild.

Thursday—

  • Cloudy with light showers possible through the afternoon.
  • Low temperature early morning 42.8º sd 2.5º (NBM model) Blue Bell
  • Mild. High temp 59.7º sd 2.0º (NBM model) Blue Bell area.
  • Winds SW–>WNW 12 mph.
Short Range Ensemble Forecast 3:00 PM Sunday. This SREF model does NOT show any drizzle, nor does the current NBM model. The higher resolution models do show drizzle.
High Resolution HIRESW-FV3 Model (Pre-release version) Simulated Radar 3 PM Sunday

I expect some clarification about the drizzle for Sunday. Stay tuned.

CHANGE IN SUNDAY’S FORECAST

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.

There’s a change in the forecast for Sunday, specifically with the timing of the rain and with frontal passage.

The latest models have delayed the cold front passage until 7-9 PM Sunday evening. The clouds and rain will similarly much occur later in the day. More sun will translate into milder temperatures.

The latest NAM-NEST delays the rain until late afternoon or evening— 6 PM or so.) The Canadian models even later.

Here’s the latest High Resolution Window (HIRESW) Model (pre-release version) simulated radar at 6 PM EST Sunday.—

HIRESW-FV3 (pre-release version) Forecast 6 PM (simulated Radar)

Thursday—

  • Cloudy with light showers possible through the afternoon.
  • Low temperature early morning 42.8º sd 2.5º (NBM model) Blue Bell
  • Mild. High temp 59.7º sd 2.0º (NBM model) Blue Bell area.
  • Winds SW–>WNW 12 mph.

 

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.

Weather… and other things "up in the air"