Hot and dry weather will continue this week with Moderate to Extreme HeatRisk persisting across much of the region. Elevated fire weather concerns will also continue. Cooler this weekend into early next week.

Excessive Heat Warning

Key Points

  • Long-duration, dangerous heat event persists this week.
  • Cooler today, then very hot again Wednesday into Friday, followed by some cooling over the weekend into next week

Discussion

Strong Delta breeze overnight, although limited associated cooling as marine layer depth remains relatively shallow at around 1K ft per Fort Ord Profiler. Morning temperatures running several degrees lower for most areas. Minor synoptic cooling expected today as upper ridge axis remains east into the Great Basin and weak upper troughing moves through. Flow through the Carquinez Strait remains strong today and tonight keeping the mercury below triple digits for Delta breeze influenced areas. NBM advertising upper 90s today for S Sac Valley while remainder of the Central Valley expected to see max T's from 100 to 110.

Upper high over the Great Basin builds back westward towards interior NorCal Wednesday pushing 850 mb temps back into the upper 20s to lower 30s Deg C. Flow through Delta also weakens Wednesday and marine layer depth trends down. Highs from 105 to 113 expected tomorrow in the Sac/Nrn San Joaquin Valley resulting in moderate to locally major heat risk.

HeatRisk WedFri

Heights/thicknesses continue to increase into Thursday, which looks to be the hottest day this week for most areas. Widespread major to locally extreme heat risk depicted for the Central Valley Thursday and in thermal belts of foothills. NBM forecasting near record highs for some locations in the Central Valley. Moderate heat risk continues for the Delta area and mountains.

587 DM cut-off upper low progged to approach the Central CA coast Friday providing minor cooling to the Delta and southern portions of the Central Valley. Highs however remain around 10-15 degrees above normal Friday and Excessive Heat Warning/Heat Advisories in effect through Friday evening.

Latest HeatRisk: wpc.ncep.noaa.gov/heatrisk/

Heat Safety Tips: weather.gov/safety/heat

Extended Discussion (Saturday through Tuesday)

HeatRisk Saturday

Synoptic cooling expected over interior NorCal next weekend as upper high resides over the Intermountain West and offshore upper low nudges towards the Central CA coast. Low progged to open to trough and lift NE over the CWA Sunday. NBM now picking up on weak forcing associated with this feature and favorable southerly mid level flow to support slight chance of an afternoon shower/thunderstorm over higher elevations of the Sierra Nevada, south of Highway 50. Low will also help to deepen marine layer and increase onshore flow. Mid 90s expected in the Delta Saturday, becoming more widespread into the S Sac Valley and N San Joaquin Valley Sunday into early next week. Triple digit heat continues in the Northern Sac Valley with mainly 80s to mid 90s for the mountains and foothills.