September 24, 2020 – Chance for a few showers over the northern Coast Range early today, otherwise dry weather expected. Temperatures close to average thru Friday, then hot weather returns over the weekend and continues next week. Breezy northeast winds develop Saturday and persist into Monday leading to critical fire weather conditions.
Discussion
Clear skies cover the region early this morning. A band of lower clouds, and a few showers, is moving through NW California early this morning associated with the approaching cold front. Onshore flow continues to spread moderating humidity inland with most areas reporting RH up around 10-30 percent compared to 24 hours ago. A few foothill thermal belts continue to see moderately poor RH with current RH only around 35-40 percent.
Cold front will washout across NW California today with perhaps a few light showers making it as far inland as western Shasta County early this morning. The remainder of interior NorCal will remain dry today with a little cooler temperatures expected as onshore flow continues.
Flow become more zonal across NorCal on Friday as troughing continues over the PacNW. A transition to light northerly flow is expected as onshore gradients slacken, and temperatures will bump up a bit inland.
The Pacific high will begin to build in Saturday and this will increase the northerly surface pressure gradient resulting in breezy north winds down the Central Valley. By Saturday evening we should see a 10-11 mb pressure gradient from MFR to SAC with breezy north winds gusting up to 30 mph into Sunday. Overnight, the northeast gradient will build in over the Sierra and this will bring increased downslope winds. These gusty winds along with hotter temperatures and lower RH will bring increased fire weather concerns for the weekend and a Fire Weather Watch is in effect Saturday morning into Monday morning.
Extended Discussion (Monday through Thursday)
Dry weather and summer like temperatures return as high pressure originating in the eastern Pacific resides over NorCal next week. Above average highs are expected each afternoon with some locations seeing multiple days of 100+ degree temperatures. Widespread moderate heat risk is expected in the Valley and foothills which could impact any sensitive groups including outdoor workers.
As high pressure amplifies through the week, winds should become lighter by mid-week with clear skies prevailing (with the exception of any smoke or haze from area wildfires). Looking a bit further, dry weather and warmer temperatures are likely to continue into the weekend.