Cold, Windy Week Ahead

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While it’s already been a fairly cool (to cold) past few days – we’re about to face an even colder pattern beginning Monday. A trough will begin carving itself into the Great Basin/Rockies over the weekend, then stretching out to extend from the central plains westward to the west coast. The trough’s jet and axis will stretch out and originate from central and northern Canada, rather than from anywhere in the Pacific, thus making this system quite dry – but cold. Currently looks like the cold front will begin sliding through far northern California late Monday night, venturing southward through Tuesday morning. Models aren’t in very good agreement with any potential precipitation from this front at the moment, with the ECMWF bringing some scattered showers through, while the GFS is nearly dry. The ECMWF’s solution would bring some snow down to about 2000ft Tuesday, with some snow locally down to 1500ft. Accumulations wouldn’t be much, but the ECMWF has been on a slow trend upping precipitation totals, but given the differences, there is potential this solution is off.


Temperatures on Monday before the frontal passage look to climb into the low to mid-50s in the valley, with continually lower temperatures the higher in elevation you go up – with lows in the 30s Monday night. Tuesday highs may be limited to the upper 40s in the valley, 30s and 40s in the foothills, and 20s in the sierra. As the trough continues digging further south, into southern California by later Tuesday, a surface low forms and strengthens in southern California & Arizona. This wouldn’t do much usually, but in this case strong surface ridging in the northern Plains into Canada makes for a very tight pressure gradient on the north side of the low, where northern California lies.


Winds begin to increase from north to south through the day Tuesday as the front continues it’s southward plunge. By afternoon, from Sacramento north, wind gusts of 30  – 35mph+ look likely. This continues through Wednesday, though winds will slowly weaken through the day in the lower elevations. The sierra & western slope will likely receive the strongest winds due to the katabatic (downslope) nature. The direction of this wind event will be out of the east to east-northeast. A bit unusual… as most of these inside-slider systems deliver more of a north to northwest wind. Thus, some places that don’t normally receive as strong of wind from northerly wind events may pick up some stronger winds. West to east and northeast to southwest facing canyons and ridges will likely receive the strongest winds as they’ll be parallel with the strong low/mid-level flow.

Forecast mean winds for Tuesday & Wednesday.

Forecast mean winds for Tuesday & Wednesday.

Tuesday and Wednesday nights the wind should keep valley areas warmer than they could be cold, even then valley lows will dip into the 30s. The breezy to gusty winds will also make wind chills a real factor, with valley wind chills in the mid to upper 20s Tuesday & Wednesday night, with potentially dangerous wind chills in the sierra in the -10 to -25 range. Valley air temperatures will likely plunge into the low 30s to upper 20s Wednesday night, with similar lows continuing through the weekend, making for what will likely be the first nights of sub-freezing temperatures for much of the valley and even inland coastal valleys, with highs in the upper 40s to low 50s.

There’s currently no significant storms being modeled through the next 7 days or so. The GFS is hinting at a change way out toward perhaps a pattern change out around the 7th of January, but the ECMWF weeklies don’t indicate much, with lots of ridging in the weeks ahead. I’ll update this post or post again in a couple days when models come into better agreement regarding any potential cold frontal snow late Monday into Tuesday.

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