January 6, 2019 – Wet weather continues today with Valley rain and periods of moderate to heavy mountain snow. Strong gusty winds in the central valley and foothills expected this afternoon and evening. A brief break in precipitation on Thursday and early Friday with a possible return of precipitation next weekend into early next week.
Latest radar imagery indicates a brief lull in precipitation across most of interior NorCal ahead of the next storm system. Lighter winds have been observed this morning, with a few gusts up to 25 mph in the northern Sacramento Valley.
Widespread precipitation will spread across the forecast area today as a storm system approaches from the west. QPF amounts suggests 0.50-1 inches in the Valley, and about 2-3.5 inches over higher terrain through early Monday.
Periods of moderate to heavy snow will develop this afternoon into the evening, with travel impacts likely.
A Winter Storm Warning continues until 10 pm Sunday for 2000 feet and above for the mountains of northern Shasta County and the far northern Coastal Range.
Storm total amounts for the northern Sierra still look to be from 25 to 40 inches, with up to 55 inches over the peaks.
A Winter Storm Warning is in effect through 4 am Monday. Mountain travel is strongly discouraged.
Another round of strong southerly winds is expected this afternoon into the evening hours as pressure gradient tightens, with gusts up to around 40-50 mph possible in the Valley and surrounding foothills.
Ridge of high pressure builds slightly on Monday, with mainly dry conditions. Some lingering light showers could be possible over higher terrain. Winds will be a little lighter, but still rather breezy.
The next storm system will impact the region Tuesday afternoon into Wednesday. This system will bring another round of widespread precipitation, but with higher snow levels. This system will be less wet as well, but accumulating snow could bring some travel delays at the pass levels.
Extended Discussion (Thursday through Sunday)
Upper ridge starts building over the western U.S. Thursday in response to an upper low digging in off the coast over the eastern Pacific. Therefore, should be a shift northward in Precipitation threat northward during the day on Thursday into the evening. Even with mostly cloudy skies Thursday, daytime highs are forecast to come in a little above normal thanks to warm air advection ahead of the offshore low.
Frontal band associated with this offshore low could begin spreading some light precipitation into the coast range by Friday morning. Timing varies a bit with this system with ECMWF a bit faster than GFS which would keep Friday morning dry. Precipitation should be spreading across the CWA Friday afternoon and night as the frontal band moves west to east across the state. As for NorCal, at this time, precipitation appears fairly limited as main energy with this system appears will track south of the CWA.
Little if any break expected early Saturday before precipitation from next Pacific frontal system starts pushing in to the north state Saturday afternoon. This time, GFS is the faster model while ECMWF would probably leave Saturday morning mostly dry, at least over the lower elevations.
Either way, Saturday night and Sunday will see another round of moderate to heavy precipitation as this frontal band pushes through. Snow levels look low enough that mountain travel impacts are likely again. Gusty southeast winds will likely add to mountain travels impacts as well.