Showers are on track for this afternoon and tonight along with a little cooler temperatures. Rainfall will mainly be confined to the mountains and on the light side. Breezy northerly winds expected on the backside of the system for Tuesday and Wednesday will result in elevated fire weather conditions.
Discussion
Surface pressure gradients continue to trend toward increased onshore flow ahead of the approaching frontal system. Satellite imagery shows some frontal cloudiness entering northwest California, but the remainder of the region is under clear skies other than some stratus beginning to nose inland south of Travis AFB, and we may see a bit of this low cloudiness around the Sacramento region early this morning. Current temperatures are mostly a little cooler compared to 24 hours ago and range from the mid 50s to lower 60s across the Central Valley.
Quick moving system still on track to move through NorCal this afternoon through tonight, and be east of the area on Tuesday. Strong vort forecast to swing inland through the base of the trough (along 40N) this evening, and may see some moderate to brief heavier showers over portions of eastern Shasta and Tehama Counties as it does (HREF indicating 50-60 percent chance of greater than 40 dBZ). Otherwise QPF expected to be on the light side with generally a quarter to half an inch possible over the northern Sierra (mainly north of I-80) and Cascades with little or none over most of the valley.
Breezy south to southwest winds are expected over much of the area this afternoon and tonight as the front approaches and moves through. Gusts of 15-25 mph will be likely through the valley while the Sierra/Cascade crest may see gusts of 30-40 mph.
Elevated fire weather conditions will likely develop behind the system on Tuesday as northerly winds increase and humidity lowers. The MFR-SAC surface gradient is forecast to increase to around 6-8 mbs on Tuesday resulting in widespread gusts of 15-30 mph. Lighter northerly breezes will continue Wednesday and Thursday along with warming temperatures. Highs are likely to return to the upper 80s to lower 90s across the Central Valley by Thursday (around 5-10 degrees above average).
Extended Discussion (Friday through Monday)
Ensembles and clusters in good agreement with weak flow pattern developing over NorCal this weekend into next week, as broad ridging develops. Weak trough along the west coast will likely cut-off within the ridge and drift south towards SoCal through the period. Dry conditions with near to slightly above normal temperatures and light winds are expected in this pattern.