Dry weather with warm temperatures today. Cooler temperatures beginning Wednesday with a chance of precipitation over weekend.
Weak trough that has been over the area will flatten as it moves east towards the Great Basin today with a more weak zonal flow pattern replacing it. This will allow temperatures to rise a couple of degrees versus yesterday with Valley highs from the upper 90’s to low 100’s. These readings are 10 to 15 degrees above normal for this time year. Moderate heat risk will affect those engaging in outdoor activities today. Have opted to use the NBM 90 percent guidance for today’s high temps, as operational NBM has been running about 5 degrees too cool over the past few days. Went back with operational NBM for temps during the cooling trend heading into the weekend.
Trough will gradually deepen over the Pacific Northwest Wednesday through Friday with lowering heights and onshore flow developing over Northern California. This will bring a cooling trend with Valley highs cooling back into the upper 80’s to mid 90’s Wednesday and then 80’s Thursday and Friday. There will also be a gradual increase in mountain and ridgetop winds progressing towards the weekend. Fire weather threat will be mitigated somewhat by increasing relative humidity values.
Extended Discussion (Saturday through Tuesday)
Pacific frontal system progged through interior NorCal over the weekend. Models continue to differ with progression and depth of this wave. NBM slowing progress of baroclinic zone into the CWA with each run Saturday which is similar to deterministic models. Overall weekend QPF looks light with main precip chances over the mountains/foothills and northern/central Sacramento Valley. EPAC high begins to build back inland over NorCal early next week. Below normal high temperatures forecast through the extended forecast period.