Elevated fire weather today in the lower elevations, Sierra showers and thunderstorms possible

April 21, 2021 – A few showers and thunderstorms linger in the Sierra south of Tahoe today. Otherwise, dry and warmer weather returns through the end of the week. Chance of precipitation returns this weekend.

Discussion

Satellite imagery shows the low now to the southeast of the Sacramento area continuing to gradually move southeast. Radar still indicating scattered showers over the Sierra Nevada from about the Lake Tahoe area southward. A few of these showers are working their way west down into the foothills before dissipating. Otherwise, skies are clearing out across the remainder of the region. Current temperatures are running around 5 degrees cooler compared to 24 hours ago across most of the region.

Low moves into southern Nevada by this afternoon, but weak trough hangs back into NorCal today. Highs today will be up a bit across most of the area, and the Sierra south of Tahoe will continue to see a threat for showers and a few late day thunderstorms.

The northerly surface pressure gradient will increase across NorCal resulting in gusts up to around 30 mph across the northern Sacramento Valley and along the western edge. Combined with low humidity (minimum RH in the upper single digits and low teens), this will result in elevated fire weather conditions as most of this area saw only spotty light showers yesterday.

Upper level ridging builds in Thursday and that will bring a period of quiet weather with warm and dry conditions into Friday with less wind. A short wave trough will approach the northern part of the state Friday night and we could see a few light showers develop over the Shasta County Mountains overnight. Precipitation chances may spread south to about I-80 by later Saturday.

Extended discussion (Sunday through Wednesday)

A trough axis will be approaching the California coast on Sunday, moving across the area through early next week. Much cooler weather is expected along with Valley rain and mountain snow chances during this time. The best chances for widespread precipitation looks to be Sunday, with the foothills/mountains favored for Monday into Tuesday.

Snow levels do look to be slightly below pass levels so some mountain travel impacts are expected for Sunday into Monday.

After Monday, clusters vary a bit between continued troughing across the area or ridging briefing building back over Northern California. Would expect some warmer temperatures to occur if the latter did occur.