Below normal temperatures today, with a gradual warming trend beginning Wednesday and continuing through the rest of the week and into next week. Onshore flow persists, with breezy to gusty late day winds, strongest in the Delta.
Key Points
- Below normal high temperatures today, then gradual warming trend arrives Wednesday through next week.
- Smoke and haze from California fires will continue to impact the northern Sacramento Valley and adjacent foothills.
Discussion
We will see slightly cooler than normal high temperatures around the region once again today as weak troughing to our north continues to move off to the east. Today will be our final day of below normal temperatures before a gradual warming trend begins tomorrow for NorCal. Upper level ridging is forecast to fill in over our area as the vacating trough will move near Montana. The increase in heights will usher in a gradual warming trend for the area through the rest of the week. While the warming trend begins, overnight recoveries will help keep overnight temperatures in the low 60s to mid 70s, which will help keep HeatRisk in check in the short term. HeatRisk will remain Minor through Wednesday, then Thursday and Friday widespread Moderate HeatRisk will return to the region.
The ridging will continue to build in the desert SW as we move through the rest of the week. Monsoonal moisture will attach itself to the peripheral of the ridge and move towards the north Friday and introduce chances of showers and isolated thunderstorms along the Sierra Crest. Ensemble precipitable water anomalies show modest moisture content (150-180%) along the Sierra crest, and medium range forecast soundings show some elevated instability as well.
The National Blend of Models is currently projecting around a 10-15% probability of thunderstorms Friday afternoon and evening as a result of the previously mentioned factors. The ridge is forecast to persist as we enter the extended forecast period and keep shower and thunderstorm chances along the Sierra crest as we move into the weekend.
Extended Discussion (Saturday through Tuesday)
The weekend will bring much of the same weather wise as the work week, warming temperatures and isolated (10-20%) chances of thunderstorms in the northern Sierra. The return of widespread triple digit temperatures appears most probable on Saturday, where the NBM is showing a 45-95% chance of exceeding 100 degrees across the Sacramento and northern San Joaquin Valleys.
Temperatures will continue to be in the triple digits around the area as we move into next week as well. Widespread Moderate HeatRisk will continue through Monday, then on Tuesday areas of Major HeatRisk in the Foothills will begin to enter the forecast. Ensemble guidance and cluster analysis are in good agreement of this pattern continuing beyond the forecast period, so a potential extended stretch of triple digit temperatures and afternoon/evening mountain showers/storms is appearing likely.