textproduct: San Joaquin Valley

UPDATE

Aviation and Air Quality Sections Updated

KEY MESSAGES

1. Moderate Heat Risk will be present for much of the lower elevations today and Wednesday.

2. There is a 5 to 10 percent chance for thunderstorms in the Sierra Nevada this afternoon and evening. Near-zero chances for the remainder of the week.

3. Drier air will cause minimum relative humidity to fall between 15 and 20 percent for much of the San Joaquin Valley through the forecast period.

4. A minor cooling trend arrives later this week, then expect steady and seasonably warm temperatures into the weekend.

DISCUSSION

High pressure building over central California today will cause temperatures to warm up to ten degrees above season averages for this date. For the San Joaquin Valley south of Fresno, there is a 40 to 80 percent chance for maximum temperatures to reach 100 degrees or more this afternoon. A small amount moisture due to southwest flow in the mid levels may result in thunderstorms over the crests of the Sierra Nevada later today, though chances are only at 5 to 10 percent.

The central area of high pressure is expected to move further off the Pacific coast overnight, setting up a zonal flow pattern and subsequent cooling trend through Friday. For the weekend, the ridge of high pressure is favorable to slide over the Four Corners region, allowing a trough to pass through the Pacific Northwest and Northern California regions which will cause a stronger decrease in temperatures to near normal.

With the upcoming pattern, minimum relative humidity is anticipated to decrease as well, with widespread 15 to 20 percent across the San Joaquin Valley through into next week. These conditions paired with cured fine fuels across the area will continue the threat for grass fire development. Minimum RH values will also lower under 15 percent in the Sierra Nevada closer to the weekend. Drying 100 hour fuels will increase the risk for fire development in these areas, though 1000 hour fuels still remain near average.

AVIATION

06Z Update:

VFR conditions will prevail for the next 24 hours across the Central California Interior.

AIR QUALITY ISSUES

ISSUED: 06/10/2025 14:18 EXPIRES: 06/11/2025 23:59 None.

CERTAINTY

The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information and/or to provide feedback.

HNX WATCHES/WARNINGS/ADVISORIES

None.