Triple digit heat returns to the Central Valley through the weekend, peaking today and Wednesday. Monsoon moisture may produce isolated showers and thunderstorms over the high Sierra south of Highway 50 late this week. Heat Advisory from 10 AM this morning to 10 PM PDT Wednesday.
Discussion
Skies are clear across interior NorCal early this morning as water vapor imagery shows the closed low now drifting south of the Bay Area. Surface pressure gradient is now solidly offshore with just a trickle of onshore gradient lingering through the Delta.
Northerly wind gusts of 15-25 mph are present in the northern Sacramento Valley and along the western edge. In the northern Sierra, local northeast to east gusts of 25-45 mph are present in the usual windy spots over the west slopes. Current temperatures are quite mild, ranging from the mid 60s to around 80 across the Central Valley (considerably milder in most areas compared to 24 hours ago.
Hot weather expected the next several days as the low drifts south off the central California coast. Widespread moderate, to locally high, heat risk is expected across the valley and foothills. Offshore (north to east) winds will peak this morning, then subside this afternoon as surface pressure gradient relaxes.
Risk of elevated convection increases Wednesday night and continues Thursday morning across the northern San Joaquin Valley and Motherlode as the low draws monsoonal moisture northward as it edges closer to the coast. There’s potential for some lightning with limited rainfall with this activity, but at this time it appears the best potential will be south of the area. Enough moisture lingers late in the week for daily diurnal deep convection along the Sierra crest beginning Thursday.
The summer solstice was at 2:13 AM PDT.
Extended Discussion (Saturday through Tuesday)
Cluster analysis advertises broad ridging over most of western North America in the extended. This will result in Valley highs holding in the upper 90s/100s through the weekend and into early next week.
Occasional afternoon/evening onshore breezes may help moderate temperatures in the vicinity of the Delta.