December 11, 2018 – Another weak weather system will brush across far northern California tonight, otherwise dry weather will continue until the end of the week when a more active storm pattern returns.
Satellite imagery shows an extensive area of fog and stratus along the eastern edge of the Central Valley from south of KMYV southward into the San Joaquin Valley. Elsewhere, skies are mostly clear other than some low clouds over portions of the northern Sierra. Northerly winds are helping to keep the north end of the Sacramento Valley fog-free and is leading to milder temperatures. Readings elsewhere across the valley are cooler compared to 24 hours ago and are currently in the mid 30s to lower 40s.
Dry weather pattern continues for the most part over the next several days. Another weather system will brush the far northern portion of the state tonight bringing a chance of showers. North winds will increase in its wake on Wednesday becoming locally breezy through portions of the Sacramento Valley.
Wetter pattern expected to initially return beginning Friday as a somewhat stronger system spreads precipitation chances further south.
Extended Discussion (Saturday through Tuesday)
Start of extended period Saturday looks dry under brief upper ridging over the western U.S. Can not rule out all precipitation chances completely, however, as ECMWF slips a shortwave over the ridge bringing some light precipitation to the northern mountains. GFS remains dry on Saturday but either way impacts will be minor as qpf will be quite light. Precipitation is forecast to begin pushing in from the west overnight Saturday as a Pacific frontal system pushes on to the coast. Impacts to the coast range should be fairly minimal as snow levels are above 5000 feet in this area but moderate rainfall is indicated. This slow moving system is forecast to begin pushing into the central valley by Sunday afternoon and into the Sierra Cascade range by Sunday night. Timing and strength of this system varies by model somewhat so confidence is not high. Current snow levels and QPF however would indicate several inches to over a foot of snow possible at pass levels or in other words a reasonably impactful weather system. Breezy southwest winds ahead of this system will add to the mountain travel impacts.
GFS drys things out Monday while slower ECMWF lingers showers over the region on Monday. Both GFS and ECMWF indicate ridging next Tuesday for drying most areas but both bring overrunning precip across the northern zones so some areas to the north may not see drying on Tuesday.