September 1, 2018 – Dry with warming temperatures into Sunday, then gradual cooling next week. Areas of smoke and haze from wildfires will continue.
DISCUSSION
Upper troughing pushing into the Great Basin this morning with upper ridging off the CA coast. Marine layer has deepened to around 1800 feet at Ft. Ord in response to troughing and flow through the Carquinez Strait is strong attm. Delta breeze however is expected to decrease during the morning hours. Surface high pressure extends inland into OR. As a result, KMFR- KRDD pressure gradient has trended up overnight to over 6 MB.
Expect some northerly wind this morning in the Northern Sacramento Valley and locally in adjacent foothills. Wind speeds do not look very strong, typically 10 to 15 mph, as upper level support is lacking. Gradient weakens later this morning, then strengthens again tonight into early Sunday. Low level northerly wind may help to drive some smoke from the Hirz fire southward into the Central Valley this morning. Warming trend continues Sunday with above normal temperatures forecast.
Triple digit heat is possible in portions of Shasta county tomorrow. Breezy conditions expected in the Delta late afternoons and nights, especially Sunday night. Gradual cooling trend begins Monday and continues through next week. Heights trend down over NorCal and onshore flow increases as long wave troughing deepens off the West Coast.
EXTENDED DISCUSSION (Wednesday THROUGH Saturday)
NorCal is forecast to remain under upper level southwest flow between high pressure over the western U.S. and a deepening trough over the eastern Pacific. Daytime temperatures are forecast to start out just a bit above normal Wednesday then drop slowly to a little below normal by the end of the week. Stable southwest flow across the north state will keep any thunderstorm threat out of the forecast through the extended. Breezy afternoon winds are likely over the Sierra as the eastern Pacific trough moves closer to the coast then lifts into the Pacific Northwest Friday and Saturday.