Hot weather continues today with Major to Extreme HeatRisk persisting across much of the region. Elevated fire weather conditions will also continue. Isolated shower and thunderstorm chances thru Sunday, mainly near the Sierra crest. Not as hot beginning Sunday and into next week.
Key Points
- Long-duration, dangerous heat event persists today, then not as hot into the middle of next week.
- Isolated showers/thunderstorms thru the weekend, mainly along the Sierra Crest.
- Red Flag Warning for Fire Zones 221 and 269 for elevations greater than 6000 feet.
Discussion
Satellite imagery shows mid and high level clouds continuing to spread northward into NorCal around the periphery of the upper high to our east and the low off the coast. TPW forecast to increase to around 0.75 to 1 inch today as the elevated moisture moves into the region. Thunderstorm chances today and Sunday are expected to be mainly diurnal and terrain driven with the highest coverage along the Sierra crest with generally southerly steering flow. Given the moisture increase, these storms will likely be accompanied by some decent rain cores, but risk of lightning occurring outside the cores on fuels that have been heating and drying the past 2-3 weeks is the reason for the Red Flag Warning over the high Sierra into Sunday evening.
Elsewhere, some sprinkles or light showers will be possible, but lack of deeper elevated instability and lift (upper low forecast to remain far enough off the coast) precludes a more widespread thunder risk. The moisture lifts out of the area by Sunday evening.
Otherwise, hot weather will persist as the overall pattern remains relatively unchanged from Friday with widespread Major to Extreme HeatRisk continuing today (Heat Warning/Advisory products remain in effect thru this evening). The increase in clouds may shave a few degrees off highs today and a transition toward onshore flow will bring some modest cooling to the Delta and southern Sacramento Valley.
It won’t be quite as hot beginning Sunday and continuing into early next week as a weak trough develops along the coast nudging the strong ridge further to the south and east.
Extended Discussion (Wednesday through Saturday)
Weak upper troughing extends over interior NorCal midweek with near seasonal high temperatures projected by the NBM. Heights then slowly trend up through the remainder of the week into the weekend as the Desert SW high builds westward. High temperatures increase each day with triple digit heat returning throughout the Central Valley by Saturday. NBM keeps the forecast dry through the extended, but will need to watch for potential deep moist convection near the Sierra Nevada crest Friday afternoon as some guidance is hinting at.