Mostly dry with near seasonable temperatures into next week. A few isolated thunderstorms mainly near the crest south of highway 50 this afternoon.
Upper high is over the Rockies with upper low moving into British Columbia and a trough extending south along the West Coast. monsoon moisture is streaming north between these features into California. A weak low pressure wave embedded within this flow is tracking across SoCal.
The upper trough along the coast has trended deeper and farther east over the past few model runs. This has pushed the best moisture and instability into Nevada instead of allowing it to flow northward into Northern California. As a result, very little thunderstorm activity has moved northward overnight. Current Cams/simulated radar ensemble model runs keep convection confined to the Sierra crest south of highway 50 today. Also, with PWAT values near 1.50 inches any thunderstorms that develop are likely to be wet. After coordination with surrounding California and Nevada forecast offices we have decided to cancel the red flag warning for dry and abundant lightning, given the minimal threat.
Upper trough will remain off the coast and transition a bit east and gradually flatten through the week. The proximity of the trough will keep some afternoon gusty winds through the Delta with onshore flow and also over ridges and up mountain valleys with enhanced gradient through the week. High temperatures will remain near normal through Friday with readings 90 to 100 for valley locations. We are currently near the climatological warmest time of the year.
Extended Discussion (Friday through Monday)
Ensemble guidance keeps NorCal under broad upper-level ridging with a weak trough off the coast late this week and next weekend maintaining southwesterly flow over the region. Highs will be close to average, and this pattern will be favorable for a decent Delta Breeze into the Central Valley, but mild overnight lows will persist in the thermal belts. Another surge of elevated monsoonal moisture may lead to an increasing chance of late day thunderstorms over the northern Sierra early next week.