Elevated fire weather conditions through Friday morning from locally gusty winds and low relative humidity. Next week, another weather system is set to bring widespread precipitation chances and isolated thunderstorms. Slight warming through the end of the week followed by more cooling.
Discussion
Current satellite imagery shows mostly clear skies across interior northern California early on this Thursday morning. Temperatures are currently in the 50s to 60s in the Valley and foothills, and in the 40s to 50s in the mountains, valid at 230 AM PDT. The weather system from yesterday continues to shift eastward and exit the region today, leaving some residual breezy to gusty conditions.
Behind the passage of this system, increased northerly winds are in the forecast for today. The National Blend of Models (NBM) suggests a 40 to 90 percent probability of wind gusts of 25 mph or greater through the day today, mainly along the I-5 corridor and in the higher elevations of the Coastal Range and Sierra Nevada where winds are the strongest. Elevated fire weather conditions continue through Friday morning from dry conditions and periods of gusty winds.
Winds become more northeasterly/downslope overnight tonight. These winds will be locally gusty, especially in the typical wind-prone areas such as gaps and canyons. These gusty conditions, combined with locally poor relative humidity recoveries will lead to several hours of Red Flag conditions overnight, mainly for the foothills and mountains. These conditions will not meet the temporal requirements for a product issuance, as winds are expected to weaken moving into the afternoon and evening hours with increasing humidity values into the weekend.
Temperatures warm slightly through the end of the week (but still remain around normal for mid September climatology), and then cool over the weekend and into next week due to an approaching weather system. Forecast highs for the Valley are generally in the mid 80s to low 90s through Saturday, and then around the mid 70s to low 80s on Sunday. Precipitation chances then return to the forecast on Sunday afternoon as the aforementioned weather system approaches the area, with unsettled weather continuing into the extended forecast period as well.
Extended Discussion (Monday through Thursday)
Ensembles support a cool and unsettled weather pattern for the region much of next week with both the GEFS and EC pointing at Monday and Wednesday as seeing the best potential for showers and thunderstorms. Clusters also show pretty good agreement for the Monday system with more uncertainty by the middle of next week.
Current QPF is generally for less than 0.25″ in the valley with 0.25″ to 0.50″ over the mountains. Portions of the High Sierra may see a few inches of snowfall accumulation. Additionally, temperatures are forecast to be around 10-15 degrees below normal.