April 16, 2020 – Dry with above average temperatures through Friday, except for a chance of late-day showers and thunderstorms over the Sierra Nevada. Cooler over the weekend with an increasing chance of precipitation early next week.
Discussion
The area is sandwiched between an upper low off the coast and an upper trough that extends from the Rocky Mountains into the Great Basin. This will tighten the gradient to bring gusty northerly winds over the Northern and Central Sacramento Valley this afternoon into early Friday. Gusts up to 20 to 30 mph are expected in that area this afternoon, up to around 20 mph Friday.
Afternoon/evening showers and thunderstorms are possible today over the northern Sierra south of I-80 as the low draws in some moisture. This potential increases Friday as the upper low off the coast moves inland through Socal, with the potential for isolated thunderstorms expanding through the Motherlode and potentially into the northern San Joaquin Valley. Elsewhere, this will bring increased clouds and cooler temperatures from Friday into the weekend. Additional mountain showers are possible over the weekend, but the forecast is trending dry, per ensembles and NBM.
Ahead of this system Valley high temperatures will be near 80 degrees today, 70 to 75 Friday and Saturday, then cool to 65 to 70 Sunday.
Extended Discussion (Monday through Thursday)
A Pacific trough is progged to push inland early next week, bringing mostly light precipitation on Monday. Precipitation totals from this system will be less than 0.05″ in the Valley, with 0.10″-0.25″ over the foothills and mountains. A few inches of high elevation snow could be possible in the Sierra and Lassen National Park, generally above 7,000 feet. Minimal mountain travel impacts are anticipated. Confidence in this precipitation event is still low at this time due to significant model spread, but it appears that best precipitation chances will be over the Sierra. While a few Sierra showers could linger into Tuesday, much of the region will dry out as ridging builds in after the system departs. Daytime temperatures will be on the rise heading toward the middle of next week, with mid to upper 70s in the Valley. A weak system may brush across the far north by midweek, and bring some light showers to the northern mountains.