September 6, 2020 – Dangerous, record-breaking heatwave will impact the region through the weekend into Tuesday. Critical fire weather concerns will return Monday night through early Wednesday with north to east wind and low humidity. Smoke and haze from wildfires will continue to impact air quality and temperatures.


600 DM upper high centered over the Great Basin expands NW into NorCal today resulting in height and thickness rises. Thus AMS will further heat up today under increased subsidence, however smoke from wildfires will likely continue to have some impact on max temperatures. Record highs likely to occur today at select locations as 850 mb temps rise to around 30-32 deg C. Today looks to be the hottest day of the heat wave for most locations.

Upper high shifts into Central CA tonight and weakens slightly into Monday. Record heat continues Monday with most locations within a degree or two of todays max temps, barring any smoke influence.

EPAC surface high builds through Oregon into the Great Basin Monday night into Tuesday as short wave troughing digs into the Intermountain West. North to east surface wind increases over interior NorCal late Monday night into Tuesday morning in response to tightening low level pressure gradient.

Given hot temperatures low RH, and dry fuels, the increased wind will result in critical fire weather conditions over much of interior NorCal late Monday night through Tuesday. 850 mb temperatures lower about 1 to 2 Tuesday, but triple digit heat will continue in the Central Valley. Guidance suggest highs Tuesday will be anywhere from about 3 to 8 degrees lower, with more significant cooling in the mountains.

Extended DiscussioN (Thursday through Sunday)

Hot and dry pattern continues later in the week as strong ridge remains over NorCal. Temperatures will remain well above average (around 10 degrees).