A rather impressive late-September heat wave will envelop all of CA by Monday. An unseasonably strong high pressure are will build in from the Desert Southwest in the coming days, bringing very warm to hot temperatures to much of CA. Highs will not be extremely high, but in many warmer places will probably eclipse the century mark. More notable will be the long duration of the expected heat event (7 days or more), the widespread nature of it, and the fact that overnight temperatures may not fall below 70 degrees, even in the normally ocean-cooled Bay Area. Fire danger will be extremely high, despite recent precipitation in the North, due to extremely low humidity and occasional moderate offshore winds up to 25-35 mph. Record high temps and record high minimum temps are likely to be set in many parts of NorCal. The ECMWF and GFS both show deep southerly/southeasterly flow over CA next week, but only the ECMWF shows a possible subtropical moisture tap. We’ll see. Attm…there are few indications of rain of any sort for the next 2-3 weeks.