April 15, 2020 – Dry with above average temperatures through Friday, except for a chance of late-day showers and thunderstorms over mainly the Sierra Nevada. Cooler over the weekend with an increasing chance of precipitation early next week.

Discussion

Other than a few high clouds moving down from the north, skies are clear across interior NorCal. Northeast winds are considerably lighter across the northern Sierra compared to 24 hours ago with local gusts only in the teens mph early this morning. Current temperatures range from the lower 30s in the mountain valleys, to the upper 40s to mid 50s across the Central Valley. Milder locales in the foothills thermal belts are in the upper 50s to mid 60s.

Mild temperatures will continue across the region through Friday with highs running around 5-10 degrees above average. The weak closed low off the PacNW will drop southward the next several days, but it will stay offshore NorCal just inside 130W. The system will bring enough cooling aloft for a chance of late day showers and thunderstorms over the mountains on Thursday and Friday.

Stronger onshore flow will bring a return of cooler temperatures beginning Saturday as westerly flow begins to undercut the eastern Pacific ridge.

Extended Discussion (Sunday through Wednesday)

Model guidance indicates increasing precipitation chances late Sunday into Monday, as a trough moves into the region. This system could bring Valley rain and high elevation mountain snow, as well as some cooling. Preliminary QPF amounts indicate generally less than 0.10″ in the Valley, and 0.25″-50″ of liquid precipitation over the mountains. Confidence in this precipitation event is low at this time due to significant model spread. At this point, minimal mountain travel impacts are expected as snow levels will remain relatively high, generally above 7,000 feet. Except for some lingering mountain showers on Tuesday, dry conditions return to most areas as the system pushes into the Four Corners region. Some light showers are possible across the northern mountains Wednesday afternoon, as a weak system skirts the far north.