textproduct: San Joaquin Valley

KEY MESSAGES

1. Major Heat Risk for the Indian Wells Valley, Mojave Slopes and Desert, with an Extreme Heat Warning in effect through next Monday.

2. Prolonged heat is expected to affect the SJ valley and adjacent foothills this weekend into early next week with a Heat Advisory in effect from Saturday afternoon through next Monday.

3. Drier conditions will develop with the warming temperatures, leading to increased fire weather concerns into this weekend.

DISCUSSION

A ridge of high pressure is in the process of tracking westward and will build over central and southern California for the coming weekend. The increasing pressure over the region will bring warmer temperatures to the region, particularly for the lower elevations of central California, including the San Joaquin Valley and the Mojave Desert. Across the entire region, afternoon highs are expected between 5 and 10 degrees above season averages. For Sunday, there is a 50 to 60 percent probability for valley temperatures to exceed 105 degrees, which increases to 80 to 90 percent for the desert. Minimum temperatures in the Mojave in the mid-to-upper 70s will provide little relief at night and has a Major Risk for heat-related illnesses for much of the population. A Heat Advisory will go into effect for the San Joaquin Valley Saturday at noon and remain in effect until 11 PM Monday; additional foothill areas such as the Coastal Range and Lake Isabella are included. An Extreme Heat Warning remains in effect for the desert areas until 11 PM Monday.

Warmer temperatures will result in a drop in relative humidity across the region, with valley and Sierra minimums ranging between 10 and 20 percent each afternoon starting Saturday. MinRH values in the Kern Desert are expected to be in the single digits through most of the upcoming week. While winds will largely be light and diurnal, the hot temperatures and low relative humidity brings about elevated concerns for fire weather, with ERCs (Energy Release Component) approaching the maximum so far this year. Downsloping winds along the Mojave Desert Slopes in conjunction with the high pressure will further highlight to risk for fire development, as there is a 70 to 80 percent probability for maximum gusts to exceed 35 mph on Monday.

The aforementioned ridge will maintain its hold over central California for much of the upcoming week, eroding slightly towards the middle of the week. This will lead to a slight cooling trend, but only by a degree or two. Afternoon highs will continue to be above season averages across the region. In the San Joaquin Valley, there is an 80 to 90 percent probability for highs to exceed 100 degrees each day through at least Friday.

AVIATION

VFR conditions will prevail for the next 24 hours.

AIR QUALITY ISSUES

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

Extreme Heat Warning until 11 PM PDT Monday for CAZ337>339. Heat Advisory from noon Saturday to 11 PM PDT Monday for CAZ301>317-319-321-332-334>336.