Unseasonably hot weather continues this week with the hottest temperatures expected today. This heat is expected to last through the weekend with Moderate to Major HeatRisk over the Valley and foothills.
Discussion
Well above normal temperatures continue today as widespread 100s are forecasted throughout the Valley and upper 70s to mid 90s across the mountains and foothills, respectively.
A Heat Advisory is in effect for elevations below 3000 feet through 11 PM tonight. Widespread Moderate to Major HeatRisk persists over the Valley/foothills with hottest temperatures across the Delta and Northern San Joaquin Valley. NBM probabilities show a 50-90% chance of afternoon highs greater than 100F degrees, highest over the Delta, Northern San Joaquin, and the Motherlode. EFI (Extreme Forecast Index) values continue to show the possibility of the need to extend the Heat Advisory through tomorrow afternoon as the Southern Sacramento Valley, Delta, Motherlode, and Northern San Joaquin Valley show above normal temperatures to persists. For areas north of I-80, HeatRisk and EFI values trend down tomorrow into the weekend.
Ridging over the Eastern Pacific will remain over CA through today before it shifts into the southwest US as troughing extends from the Pacific NW and a secondary trough off the far southern CA coast Thursday afternoon. The trough passing through the Pacific NW will help flatten the ridge briefly but high pressure resurges over the area this weekend. Ultimately, this will keep above normal temperatures in our forecast through the reminder of the week with 90s in the Valley and 70s to low 90s across the mountains to foothills respectively.
Additionally, dry conditions are expected each day this week, although we can see small incremental increases in moisture through Saturday. Afternoon humidities range from 10 to 25 percent, driest over the Northern San Joaquin.
Winds are not expected to be anything more than seasonal breezy weather at times, so forecast remains under Red Flag criteria.
Extended Discussion (Sunday through Wednesday)
Ridging will remain over the area, keeping above normal temperatures apart of our forecast into early next week albeit not as hot as this week. Late next week looks to be the first chance of any significant weather pattern change and cooler weather.