Hot weather will continue this week with breezy winds through the Delta. Isolated thunderstorms are possible across the area today and across the Sierra the rest of the week. Monsoon moisture will push northward this week with isolated thunderstorms possible in the Valley/Foothills today and across the Sierra for the rest of the week.
Discussion
KDAX radar is spinning in precipitation mode this early Tuesday morning as elevated convective showers impact portions of the Sierra around/south of Tahoe as well as the northern San Joaquin Valley. Weak upper-level low spinning counterclockwise off the Central Coast has promoted northbound moisture advection, helping spark some of these showers. Now, instability isn’t the greatest, therefore think we’ll be limited to isolated showers/thunderstorms. With the dry low-levels, very little precipitation is expected to make it to the ground — if any.
Best chance for any measurable precipitation (as little as it may be) would be in the Sierra. As of this discussion publication time, have not observed any cloud- to-ground lightning strikes in our area; only a handful of cloud- to-cloud strikes in San Joaquin County. This is something that will be monitored very closely through the rest of the overnight hours and into the day as convective chances continue.
Outside the slight chance of showers/thunderstorms, main story for the next several days will be the heat across the northern third of California. Upper-level ridge will setup residence over northern Nevada, and will bring above-normal temperatures to the Pacific Northwest and south into northern California.
Most impacted areas in our area would be much of Shasta County and into parts of Tehama County (i.e., northern Sacramento Valley), as well as the adjacent foothills.
Day-to-day forecast trends with the National Blend of Models have nudged upward by a few/several degrees. Thursday appears to be the hottest day with the National Blend of Models giving Redding a 60% percent chance of hitting at least 110 deg F.
The hot afternoon highs and very warm overnight lows in the 70s will result in moderate to high heat risk. Consequently, have opted to issue an Excessive Heat Watch from approximately Red Bluff and points north for both Thursday and Friday. Temperatures in the southern Sacramento Valley and northern San Joaquin Valley are not forecast to be as anomalously hot with highs in the middle 90s to low 100s through the work week.
Extended Discussion (Saturday through Tuesday)
Cluster analysis continues to show broad ridging over much of western North America through the weekend. This will result in triple digit heat continuing for the northern/central Sacramento Valley, though likely not as hot as Thursday/Friday.
Redding currently stands at 16 consecutive days at/above 100 deg F, and the present forecast looks to add at least 7 more. All-time record for the most consecutive triple digit days for Redding area is 26, from Jul 17 – Aug 8, 1978. Afternoon/evening showers and isolated thunderstorms will be possible through the weekend generally along/south of I-80.