Fall not far off in CA

A brief update is in order this evening. A side note: the Seasonal Outlook will be completed by this coming Sunday, and likely by Friday afternoon. Thank you for being patient.

 A significant change in the long -prevailing slate summertime pattern will occur this week. Yesterday, some mid-level moisture and dynamics in NorCal led to scattered elevated convective activity, with scattered very brief showers and very isolated cloud to ground lightning strikes. Up to 30 lightning-started fires have been reported thus far.

Prominently features in satellite imagery this evening is a fairly strong cut off low in the far E. Pac. off the CA coast. This low has some convective activity developing on the cold front trailing from it, and from satellite trends it does appear that scattered showers are occuring over the water and probably some isolated lightning strikes. This low is expected to pass inland over far NorCal and the N. Sac. Valley tomorow and Friday, but will weaken somewhat as it does so. Scattered showers and thunderstorms are likely over the North Coast, the Coastal Range, and the Sierras. Isolated showers or thunderstorms are possible from the North Bay to the Northern Sacramento valley, as well, but are not likely by any means. Most significantly and probably most noticably, this low will bring much cooler temperatures and some breezy NWly winds. After the cut off low moves off to the east by the weekend, we will see some warming temps, but nothing like the last few weeks. The GFS is indiciating a very fall-like pattern for next week and beyond, with increasingly strong pacific storms moving into the Pac. NW and leaving CA essentially dry from Eureka southwards. Fall, I think, is not too far away–but the real story this winter is going to be how much precipitation falls in the North…