Above normal temperatures with dry conditions continues this week. Widespread Moderate HeatRisk with isolated areas of Major across the foothills and Valley. A reprieve from the hot weather begins late this weekend into early next week.
Discussion
A relatively quiet day is expected across Northern California, outside of smoke continuing to affect portions of the Northern Sacramento Valley and adjacent foothills. THe HRRR Near Smoke 05/00z run shows the concentration lessening throughout the morning hours before thickening in the afternoon and evening hours, still flowing to the north-northeast.
Today will see similar temperatures with highs in the upper 90s to low 100s in the Valley, albeit 1-3 degrees F cooler than yesterday. Moderate HeatRisk continues throughout the Valley this week with isolated areas of Major HeatRisk south of Hwy. 50 Tuesday and Wednesday. NBM probabilities show a 40-75% chance of exceeding 100 degrees F, primarily across the foothills and Northern Sacramento Valley. For Tuesday and Wednesday, chances increase to 50-95% with widespread 100s for the Valley expected. The warming trend settles on Thursday with slightly cooler temperatures, although still a couple degrees above normal for this time of the year.
The daily afternoon and evening threat weakens today as models project a much weaker push of monsoonal moisture, limiting the potential of any organized convection. Breezy conditions with gusts up to 15-25 MPH continues with strongest winds near the Delta and along areas of high elevation.
The Valley will see a short drying trend develop early this week with minimum afternoon humidities lowering to the low teens to low 20s across Northern CA and widespread teens by tomorrow. Incremental influxes of moisture begin midweek with areas of the Delta and Sacramento Valley seeing min. RH values up to 40%.
Extended Discussion (Friday through Monday)
Slightly cooler, near-normal temperatures persist over the area on Friday, as upper-level troughing offshore deepens and the upper-level ridging weakens. This will prompt a gradual cooling trend that will last through the weekend. Moderate HeatRisk will still be widespread throughout the Valley and foothills Friday, but areas of Minor HeatRisk start to appear beginning on Saturday. The NBM is showing a 50-85% chance of high temperatures less than 95 deg Friday- Sunday everywhere except the northern Sacramento Valley, with probabilities greater than 70% in the Vicinity Delta. As this troughing deepens and moves over Northern California late week, periods of breezy onshore flow will follow generating gusts 15-20 mph in the Valley, with gusts up to 25 mph in the Vicinity Delta. This pattern will also bring increased daytime humidity values in the upper teens to upper 20s to the Valley and foothills, and lower 30s around the Delta.