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November 16, 2020 – Dry weather today. Rain, high elevation snow, and gusty wind Tuesday and Wednesday with drier weather returning towards the end of the week.

Discussion

Scattered high clouds are moving across the region early this morning as the upper ridge moves overhead. IR difference imagery indicates patches of fog have developed in the mountain valleys, but the Central Valley remains fog-free so far. Light northerly winds have developed thru much of the valley, and temp dew point spreads are higher than 24 hours ago. Only patchy early morning fog is expected around sunrise, mainly from the Sacramento area southward.

Dry weather, with milder temperatures, is expected across the area today as the ridge shifts east ahead of the approaching trough. Highs today will be unseasonably mild, around 5 to 15 degrees above average for mid-November.
Upstream trough continues to dig which is slowing its eastward progression, but it’s also tapping deeper moisture between the West Coast and Hawaii. Winds and precipitation will pick up on Tuesday, across the northern half of the forecast area in the morning and spreading south across the remainder of the region by early Tuesday evening.

This will likely be the wettest system so far this season for much of the region. 2-3 inches of rain will be possible Tuesday and Wednesday across the foothills and northern Sierra west slopes.

We’ll take a closer look at the potential for impactful QPF as HREF short duration probabilities come into focus, particularly for the burn scars over eastern Butte and western Plumas Counties.

Significant snow and wind will also be likely across the higher elevations (mainly above about 6-6.5k ft) by Tuesday afternoon and continuing Wednesday.

The winter storm watch has been upgraded to a warning as significant travel impacts are forecast. The period of heaviest snow and wind over I-80 is expected from late Tuesday afternoon through Tuesday night with 12-18 inches possible at pass level.

Initial frontal system moves south by early Wednesday morning, but another wave moves in Wednesday continuing showers over the mountains with a chance in the valley. Showers chances continue Wednesday night and Thursday, mainly over the mountains, before tapering off early Friday.

Extended discussion (Friday through Monday)

Weak upper trough moves through Friday with little impact, followed by upper ridging Saturday. Models differ with progression of next Pacific storm with GFS bringing system inland Sunday although GEFS doesn’t really support this.

Forecast leans towards slower EC during this time frame with frontal precipitation spreading into the CWA Sunday night into Monday.