An extended period of dangerous heat expected for the holiday weekend into next week. Excessive Heat Warning from 11 AM Saturday to 8 PM Tuesday. Record heat along with very low daytime humidity will lead to increased fire weather conditions.

Discussion

Clear skies cover interior NorCal early this morning. Surface pressure gradients are nearly identical to 24 hours ago, and satellite imagery shows some stratus along the coast. Current temperatures are within a couple of degrees of what was observed 24 hours ago, ranging from the 60s to mid 70s across the Central Valley.

Southwest flow will persist for another day as a short-wave passes to our west and north. Highs today are expected to be pretty similar to Tuesday’s. Stronger warming develops Thursday and continues into the weekend as the western US ridge extends westward.

An extended period of very hot weather will continue into next week. By Saturday, widespread highs of 105-110 are likely across the Central Valley with warm overnight lows.

The Excessive Heat Watch has been upgraded to a Heat Warning in effect from midday Saturday until at least Tuesday evening.

Extended Discussion (Sunday through Wednesday)

Anomalously strong high progged over interior NorCal through the extended forecast period. Heights progged in the mid 590s DM with 850 temps in the lower 30s deg C. Highs forecast around 110 in the Central Valley Sunday and Monday with record highs likely, and potential for all time high temperatures to be set.

Overnight lows will mainly be in the 70s to 80s. As a result widespread high heat risk will occur.

Uncertainty in forecast early next week as EC bringing deep short wave trough into the PacNW Tue/Wed, weakening high over NorCal and allowing for minor cooling, while GFS maintains strong high over NorCal through midweek.