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 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 through Monday.

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

DISCUSSION

With the help of the deep upper low dropping into the Great Lakes region, the Heat Dome Weak disturbance continues to round the ridge as the heat dome is now over the West Coast. The position of the Heat Dome will now allow the region to heat up as widespread triple digit temperatures were observed this Saturday afternoon. Temperature trends, while small, continues rising today. Therefore, confidence is high that we will Heat Advisory criteria across the San Joaquin Valley and Extreme Heat Warning across the Kern County Desert this weekend. A look at the Probability of Exceedance (PoE) of reaching 105 degrees has the south end of the San Joaquin Valley more favored with Merced County in the 20-40 percent range. Will continue to evaluate Merced County during the event to update that areas likelihood of maintaining heat advisory criteria. Otherwise, a hot weekend and early next week as the ridge axis resides over the West Coast.

Looking further out into the long term, while PoE of reaching 105 degrees remains below 40 percent, PoE of 100 degrees will range from 70 to 90 percent across the San Joaquin Valley for much of next week. Therefore, well stay on the warm side as hazardous heat will be the main concern for Central California extending through the first week of August. In addition, Climate Prediction Center has the first week of August with a 65 percent chance of having temperatures likely going above normal for that period. Furthermore, ensembles have the monsoon moisture staying well to the east during the period with dry conditions prevailing at least through the middle part of next week.

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 until 11 PM PDT Monday for CAZ301>317-319-321- 332-334>336.