February 27, 2019 – Showers and mountain snow will continue into Thursday with hazardous mountain travel persists into Thursday. Mainly dry Friday, then more wet weather for the weekend.
Discussion
Satellite and radar indicating warm sector with its persistent light to moderate (occasionally heavy) precipitation finally nudging east as cold front and upper trough reach the coast. Record daily rain set Tuesday in Sacramento and Stockton. Moderate to heavy snow continues in the Sierra above about 4500 feet (per observations and profiler data) where KBLU has been inundated with several feet of snow over the past 36 hours.
Southerly winds continue to howl across the Central Valley early this morning ahead of the approaching front. Gusts of 40 kts have been reported in the past hour from Sacramento northward, and several reports of downed trees and power lines have been received.
Precipitation will quickly become more scattered this morning post-front. Upslope flow will continue abundant showers across the foothills and northern Sierra. Forecast soundings indicate some steepening of lapse rates, but lack of deeper instability and limited potential for surface heating will likely preclude much thunderstorm potential.
Flood threat will continue into Thursday as runoff works its way downstream. Many of the hydrographs for the creeks and smaller rivers have seen their peak earlier in the night, but several in the Sacramento area are seeing renewed rises early this morning resulting from last evening`s heavy rain.
Winds will also likely drop off somewhat for much of the valley (but remain rather breezy), but lingering gradient across the far northern portion of the state will likely continue gusty southerly winds for the Redding and Chico areas through the afternoon.
Cyclonic onshore flow will keep lingering showers into Thursday, mainly over the eastern portions of the Central Valley, extending into Motherlode and Sierra. Snow levels lower Thursday afternoon to around 4000 feet.
Drier weather forecast for most of the area Friday as short wave ridging moves through, then another Pacific storm tracks inland over the weekend.
Extended Discussion (Sunday through Wednesday)
The wet pattern will continues through the extended period as multiple weather systems are expected to impact NorCal. The first system moves in overnight Friday, bringing Valley rain and mountain snow through Sunday. Although model consistency is still pretty low on specifics at this point, this storm does not look to be nearly as wet as the current weather system. Liquid precipitation amounts of a third of an inch up to an inch are possible in the Valley with one to two inches possible in the foothills and mountains. Snow levels will be rising to 4000 to 5500 feet by Saturday afternoon.
A few mountain showers will linger into Monday but overall dry weather is expected as we see short wave ridging. Another wet system looks to take aim on NorCal on Tuesday into the middle part of next week. This one looks to have more moisture than the weekend system and could bring another extended period of widespread rain and snow. Confidences is low with this system at this time given how far out it is and some model disagreement but is something to keep an eye on.