September 10, 2017
Summary: Our cut off low has moved southward and is now parked about 400 miles to the west/southwest of Santa Barbara. Along its eastern flank, showers are beginning to show up on radar over the Channel Islands up to the coast of Santa Barbara County. The flow aloft above central California is now out of the southeast. This is favorable for tracking monsoonal moisture into central California.
It appears the atmosphere is ripe for thunderstorms to develop this afternoon over the Kern County mountains, the Sierra Nevada, and even the Coast Range. With the low not far off, dynamic convection will be over the valley floor for the possibility of scattered showers and isolated thunderstorms. Interestingly enough, models have been showing a swath of moisture moving around the east and northeast sectors of the low, moving showers and thunderstorms over the Coast Range just west of the San Joaquin Valley. There are certainly a lot of wild cards that will be in the forecast through Tuesday night.
The low is projected to move back towards the north Monday then will shift inland through central California Tuesday night and Wednesday. The forecast for Wednesday is a bit shaky, but for now models show most of the precipitation wrapping around the low to our north.
So, it appears the best chance for activity over the valley floor will be later this afternoon through Monday night. Even a few nocturnal thunderstorms are possible due to the instability of the atmosphere. For now, we’ll keep the forecast dry for Wednesday, but as the low moves inland, a strong on shore flow will develop, pushing marine air into the valley for a cooling trend.
Models have been fairly consistent in showing temperatures below the 90 degree mark for Wednesday.
The flow aloft for midweek on will be westerly, which will efficiently move tropical moisture east of our region. Expect dry weather Wednesday night on.
Longer term, it does not appear hot weather will return any time soon as a weak trough of low pressure will remain over the Pacific Northwest, maintaining an on shore flow. This should keep temperatures near average through next week.
Forecast: Mostly clear this morning. Partly cloudy this afternoon with a chance of isolated showers and thunderstorms, mainly near the foothills. Variable cloudiness tonight through Monday night with a chance of scattered showers and isolated thunderstorms. A slight chance of isolated showers and thunderstorms Tuesday. Becoming partly cloudy Tuesday night and Wednesday with a slight chance of showers and thunderstorms, mainly north of Fresno. Mostly clear Wednesday night through Sunday.
Temperatures: Highs today will warm into the upper 90s. Lows tonight will cool into the upper 60s to the mid 70s. Highs Monday will again warm into the upper 90s with the lows Sunday night in the upper 60s to the mid 70s. Highs Tuesday will generally warm into the mid 90s.
Next update: September 10, PM