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 with a Heat Advisory in effect through Monday.

3. Drier conditions will develop with the warming temperatures, leading to increased fire weather concerns for most of the week.

DISCUSSION

With the heat dome overhead, hot temperatures were observed across Central California. Another disturbance is round the area of high pressure and expected over the Upper Mid-West Monday Afternoon. While slight temperature changes will be observed on Monday, the strength of the high pressure will keep triple digit heat over Central California at the start of the work week. Again, temperature trends, while small, continues in a steady state fashion for the next several days. Therefore, confidence is high that we will see Heat Advisory criteria across the San Joaquin Valley and Extreme Heat Warning across the Kern County Desert on Monday. The question is how level the heat will continue over the West. Will evaluate if the Advisory and Warning need to be extended beyond Monday.

A look at the Probability of Exceedance (PoE) of reaching 105 degrees has shifted up from several days ago. While the south end of the San Joaquin Valley is still favored with Merced County now showing percentages in the 40-60 percent range. Will continue to evaluate Merced County during the event to update that areas likelihood of maintaining heat advisory criteria. Otherwise, a hot start to the week as the ridge axis resides over the West Coast.

Looking further out into the long term, while PoE of reaching 105 degrees shows a drop in percentages around mid-week, the values than trend up later in the week. Current thinking is to have the heat products go through Tuesday with a new set of heat products later this week. Climate Prediction Center has the 6 to 10 day period with a 60 percent chance of having temperatures likely going above normal for the 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 this 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.