[su_note note_color=”#d9f2da”]Updated Fri 7AM:  The GFS seems to be the most consistent model with the others trending towards its solution— A front moves through Tuesday, with some light rain, as the low pressure system develops to our north and east. The cold air arrives too late for much snow in our area.

Specifically, the cold air doesn’t come in until the precipitation is ending late afternoon or early evening on Tuesday. At best, a coating to under an inch of snow is possible Tuesday by 8 PM  with an emphasis on the lower range.

Capturing the trend is the National Blend of Models (NBM) which has been slowly reducing its snow forecast for our area.  Here’s the current NBM snow forecast for Tuesday 8 PM:

It’s likely the NBM forecast is over-done, even with its low snow totals of a coating of snow.

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…from yesterday (Thurs)—

[su_note note_color=”#d9f2da”]Updated Thurs 8 AM:  There’s still much uncertainty with a potential snowfall early Tuesday morning.  The Canadian CMC GDPS (Global Deterministic Prediction System) has sleet changing to snow here, while the GFS jumps the energy off the coast, mostly missing us.  Here’s the current Canadian model, showing the rain/snow line in red, moving over our area, changing sleet/rain to snow. Precip starts before daybreak and continues through Tuesday.  The current GFS forecast is very different with light showers, flurries.

Here’s the current GFS forecast for 8AM Tuesday, showing the precipitation has departed by the time the cold air moves in (lines depicted by arrows.)

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…from earlier this week:

As I mentioned over the weekend,  the period around Tuesday, November 12th looks to be interesting weather-wise.

Following the cold outbreak this coming Friday through Saturday, another cold outbreak is expected next Tuesday.  While this weekend’s dip in the jet stream will be broad and positively tilted, next week’s outbreak is likely to feature a highly amplified jet stream allowing development of a coastal storm.

The current Canadian model has a deep coastal storm with snow and sleet for us next Tuesday. The GFS had predicted something similar, but has recently backed away from this forecast scenario.

So there’s much uncertainty, but next Monday through Wednesday looks to be interesting.  Stay tuned.

[su_note note_color=”#d9f2da”]Friday Update 7:30AM:  Earlier Forecast Outlook is on track.

Saturday will have considerable high and high middle level cloudiness.  Some sunny breaks possible, especially during the early morning and  later at times during the early afternoon.   Clouds thicken late afternoon.  Showers possible north and west of Philadelphia during the evening.   High 68.

Sunday: Rain, starting early morning, ending mid to late afternoon.  Rain may be heavy.  Mild. High 71 [/su_note]

from earlier in the week:

I was tempted to post the weekend outlook earlier this week and I’m glad I didn’t.  The GFS weekend forecast has changed  since yesterday.

Low pressure moving up from the south was expected to approach on Saturday.  The latest GFS has slowed the approach of this system down to late Saturday— while the Canadian CMC and the European ECMWF hold the rain off until Sunday.

(When the GFS model was updated this past June to what was previously called the FV3-GFS in development, there were known biases in the new model which allowed some systems move up from the south too fast. 

The GFS is being updated on Nov 7th; it’s not clear whether this bias has been fixed.)

Currently, Saturday looks to be a decent day, with clouds moving in during the afternoon.  High 64.   Some showers possible Saturday late afternoon and evening.

Sunday looks to be rainy, especially by early afternoon.  High 67.

There is still some uncertainty with this outlook; the large spread in forecast high temps for Sunday from the EKDMOS captures the uncertainty:

[su_note note_color=”#d9f2da”]A week ago, I spoke of very cold weather arriving around Halloween.   The models still show this. Expect a winter-like cold to affect us around the end of this month. [/su_note]