Cooler through Thursday – dry & windy conditions to increase fire weather concerns this weekend

June 27, 2018 – Cooling today into Thursday with highs near to slightly below normal. Warming Friday with hot, dry, and breezy conditions over the weekend. Cooling returns early next week. Fire Weather Watch from late Saturday night through Sunday evening

DISCUSSION

Upper troughing in the EPAC approaches today and moves through Thursday. This will result in synoptic cooling with increased onshore flow and deepening marine layer. Strong Delta breeze will bring enhanced cooling into the Central Valley. High temperatures today into Thursday expected to be near to slightly below normal with 70s to 80s in the Delta and Southern Sacramento Valley with lower to mid 90s elsewhere in the Central Valley. Highs in the foothills and mountains will be mainly in the 70s to 80s.

Potential for some morning stratus in the Southern Sacramento Valley Thursday morning. Breezy southwest wind will be possible over higher mountain terrain through Thursday. Upper trough shifts east Thursday night then EPAC High builds inland Friday into the weekend. This will result in significant warming with triple digit heat returning to the Central Valley Saturday.

NAEFS Standardized Anomalies show values above 3 on Saturday with a 10 year return interval. Highs expected from 100 to 109 in the Central Valley, hottest in the Northern Sacramento Valley. Breezy northerly wind develops over portions of Interior NorCal by early Friday and persists into the weekend with lowering humidity. This will lead to significantly increased fire potential.

EXTENDED DISCUSSION (Sunday THROUGH Wednesday)

Locally breezy north winds may continue across the northern portions of the Valley into Sunday, continuing the potential for critical fire weather conditions. Onshore flow should begin to increase through the Delta at some point during the day Sunday, helping to cool locations adjacent to the Bay Area. The cooling trend becomes more pronounced next week as an upper trough sets up across the West Coast. Current model guidance has temperatures within a few degrees of normal across the region on Monday, then cooler than normal Tuesday into Wednesday.