January 17, 2019 – Showers, thunderstorms, heavy mountain snow and breezy conditions today. Precipitation chances continue through the weekend, then a pattern change to dry weather is expected for next week.
Discussion
Post-frontal airmass has settled across interior NorCal with radar indicating the bulk of shower activity now mainly over the mountains. Upslope flow and strong mid-level flow pushing around the base of the offshore trough is organizing the precipitation into lines of moderate to heavy showers over the west slopes of the northern Sierra.
Surface pressure gradients have relaxed considerably compared to last evening, but enough gradient remains for breezy to windy conditions (20-30 mph in the Sacramento Valley and 40-60 mph in the Sierra).
Runoff from yesterday’s and last evening’s heavy precipitation will continue to result in some local flooding of creeks and small rivers this morning, especially along the edge of the Central Valley and into the foothills.
Scattered showers and thunderstorms today as the upper trough lifts across the region. Higher resolution models indicate potential for several lines of showers and thunderstorms to move through the Sacramento region today beginning around late-morning and continuing into early this evening. Flash flood watch continues for the recent burn scars for potential issues with high rainfall rates associated with thunderstorms.
Heavy snow will continue across the northern Sierra for about another 24 hours with lowering snow levels. Snow levels will lower to around 5000 feet this morning and to 4000 feet tonight. 12-18 inches of accumulation is forecast around BLU with an additional 2-3 feet across the northern Sierra passes.
A brief period of improving conditions are anticipated thereafter as a transient upper ridge moves through. By Saturday morning, a shortwave moving through the Pacific Northwest will lead to some increasing precipitation chances along the trailing cold front. This is primarily a concern north of I-80 although amounts will be nothing like this current storm. An additional precipitation chance lurks in the wake to conclude the weekend.
Extended Discussion (Monday through Thursday)
Precipitation ends early Monday morning with upper level ridging rapidly building in bringing dry weather and northerly winds. Dry weather with above normal temperatures are expected through next week. High temperatures in the Valley warm up to the lower 60s with high temperatures in the mountain and foothills in the 40s.