Dry, mild and somewhat breezy today, weekends storm systems lined up to bring rain and snow

April 2, 2020 – Dry and mild weather expected this week. Breezy north winds expected today. A pair of storms move in over the weekend into early next week bringing rain, gusty winds, heavy mountain snow, and travel problems.

Discussion

The area remains between eastern Pacific ridging and a departing trough. A fairly tight north to south pressure gradient (7 mb between Medford and Sacramento) will bring breezy northerly winds today, with gusts between 20 and 30 mph.

Temperatures today and Friday will rise back to around normal levels. For the Valley, highs will be in the mid to upper 60s.

A cool shortwave from the Gulf of Alaska approaches the Northern California coast Friday night with clouds spreading across the area. Confidence on precipitation timining has improved, moving into the northern Coastal Range around midnight, then spreading southward to I-80 by late Saturday morning. Ensembles and deterministic models agree by afternoon that precipitation will be widespread across the area. Snow levels are expected to be around 3500 feet over Shasta County, 4000-5000 feet elsewhere, with accumulating snow bringing likely travel problems by afternoon.

A colder, stronger system approaches Saturday night and spreads inland Sunday. Heavier mountain snow showers are expected by Sunday afternoon, with up to around an inch an hour accumulating. This will likely make mountain travel difficult and dangerous at times. Afternoon thundertorms are possible in the Valley, especially on the west side.

Late Sunday night, snow levels could lower into the upper foothills (3000 feet), bringing some possible accumulations down to that level.

Latest guidance has a storm total of 1 to 2 feet of snow from Saturday morning through Monday morning in the mountains above 5000 feet. For the Valley and foothills, rainfall totals of 0.75 to 2 inches are possible.

Extended Discussion (Monday through Thursday)

Deterministic models have come into better agreement with handling of closed upper low along the CA coast early next week. However, differences in its meandering exist, typical for closed lows, and how quickly it progresses. This results in differences in how far north the precipitation chances extend Tuesday through Thursday. For now, forecast follows NBM guidance which keeps the forecast unsettled with the best chances for precipitation over the mountains.