Moderate heat risk with above average temperatures continue for the next week except for near normal temperatures today and Saturday. Periods of locally breezy onshore winds continue in the afternoon and evening hours, strongest in the Delta region and over the mountains.
Discussion
Onshore flow has not been as strong last evening through today’s early morning hours as yesterday, so Valley temperatures are running hotter than 24 hours ago, especially in the northern Sacramento Valley. As of 12 am, temperatures for most Valley locations in Western Colusa County and north into Shasta County were still reading in the 80s to low 90s. Delta influenced Valley areas were much cooler in the 60s to low 70s.
A week upper level trough is still slated to move through Northern California today through Saturday, which will allow temperatures to cool a few degrees today back to near the daily normal. Onshore winds will also become more elevated this afternoon and evening as the trough passes, with strongest winds in the Delta and mountains. Ensemble guidance is in good agreement that high pressure will quickly build back over the West Coast and Eastern Pacific.
Temperatures will warm back above normal Sunday into early next week with the Northern Sacramento Valley in Tehama and Shasta Counties warming the most from highs around 102 degrees today to 105-108 degrees Sunday.
Elsewhere, temperatures will remain fairly stable into early next week with temperature fluctuations of only a couple of degrees each day. Onshore flow will continue, though it will be weaker, so overnight temperatures will be warmer than previous nights, especially in the far northern Sacramento Valley and foothills.
Extended Discussion (Tuesday through Friday)
Upper level ridging is expected to continue building over the West Coast and Eastern Pacific next week with good agreement in ensemble guidance. Temperatures will remain fairly steady with only minimal day to day fluctuations. Daytime temperatures are forecast to be in the mid 90s to 106 degrees for the Valley, upper 80s to low 90s in the Delta region, upper 90s in the foothills, and 70s to low 90s in the mountains.
Monsoon moisture may make a push north into Central California late next week as the monsoon high builds to the northwest. Latest NBM has increased probability of precipitation and thunderstorms over the Sierra south of Highway 50 for Thursday and Friday, though uncertainty remains high at this time.