Moderate to heavy rain Wednesday through early next week

Dry and milder today. Precipitation chances return tonight through at least the weekend. Moderate impacts possible for Thursday into Friday due to moderate to locally heavy rain. Major impacts possible late Saturday into Monday due to heavy rain and snow.

Discussion

We’re in between weather systems with mostly clear skies covering interior NorCal early this morning. Current temperatures are mostly cooler compared to 24 hours ago with most of the Central Valley in the lower to mid 40s. The foothills and mountains are mostly in the 30s.

The break in precipitation will be short-lived today as the short-wave ridge is quickly displaced eastward by the next approaching trough. Frontal precipitation will move into the western portions of the forecast area this evening and across the remainder of interior NorCal overnight.

Breezy south to southwest winds can be expected as the surface gradient tightens. Light snowfall accumulations will be possible across the northern Sierra crest. Lighter warm-advection precipitation likely to continue across much of the area on Wednesday.

Progressively wetter systems are expected later this week with another system later Thursday into Friday. Heaviest QPF initially will be north of I-80. Snow levels will be much higher, above 9k ft, limiting snowfall accumulation to just the highest peaks. Precipitation totals for Thursday-Friday are expected to be around 2-6 inches in the mountains north of I-80 with around half an inch up to 2 inches across much of the valley and foothills.

More rain on the way over the weekend into next week!

Extended Discussion (Saturday through Tuesday)

Periods of moderate to heavy precipitation look probable during the extended forecast period as 170+ kt zonal polar jet extends across the Pacific with LFQ extending over NorCal. Large scale synoptic ascent with upper diffluent flow will result in strong UVM. Combined with associated PW plume in excess of 1.5 inches within main core will lead to significant precipitation, especially during the Sun/Mon time frame when IVT exceeds 500kg/(ms).

Liquid precip estimates at this time for the period 12z Sat through 00z Tue equate to about 1 to 4 inches in the Central Valley with 3 to 8 inches in the foothills and mountains.

Snow levels remain above pass levels over the weekend, lowering to around 5000 to 6000 feet Mon/Tue. Potential for several feet of snow over higher mountain terrain by early next week.