April 1, 2020 – Dry and mild weather expected this week. Breezy north winds expected today and Thursday. A pair of storms move in over the weekend into early next week bringing rain, gusty winds and accumulating mountain snow and travel problems.
Discussion
An upper low over western Canada and the Pacific Northwest will shift eastward today. Dry weather is expected today except for a few lingering light showers possible this morning in the Sierra north of I-80. Dry northerly flow will develop behind the departing low as Pacific ridging extends eastward. This will increase the surface pressure gradient, with some breezy northerly winds today and tomorrow. Gusts up to 25-35 mph will be possible each day in the Valley.
Valley highs today are expected to be about 5 to 10 degrees cooler than yesterday, generally in the mid 60s. This is 3 to 5 degrees below normal for this time of year. Temperatures on Thursday and Friday will rise back to around normal levels.
A shortwave progresses towards the west coast Friday night, with precipitation chances beginning early Saturday morning north of I-80, then spreading southward. Exact timing of precipitation remains somewhat uncertain, with the ECMWF slower than the GFS, but ensembles and deterministic models agree by mid-afternoon that the possibility for precipitation will be widespread across the area. Snow levels are expected to be around 4000-5000 feet, with accumulating snow bringing potential travel problems.
Extended Discussion (Sunday through Wednesday)
Stronger Pacific storm drops down the West Coast Sunday into Monday bringing widespread precipitation over interior NorCal with significant snow expected in the mountains. Snow levels range from around 3500 to 4500 feet with 1 to 2 feet possible over the higher elevations of the Sierra Nevada. Deterministic models begin to diverge significantly by Tuesday with EC keeping strong closed low meandering off the CA coast through early Thursday while GFS weakens low and moves it through SoCal Tuesday. EPS/GEFS support EC solution so attm forecast leans towards this with unsettled weather advertised through midweek.