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

Upper level disturbance now exiting the Pacific Northwest and moving through the upper Mid-West. While too far to provide Central California with weather, the disturbance will flatten the high pressure area as max temperatures across Central California approach 100 degrees. Upper 90s across the San Joaquin Valley is highly unlikely as Probability of Exceedance (PoE) of reaching 100 degrees is in the range of 80-95 percent. Therefore, confidence is low on any significant cool-down this week. The question now is can the heat products (Extreme Heat Warning and Heat Advisory) be allowed to expire before the next heat-up later this week.

A look at the Probability of Exceedance (PoE) of reaching 105 degrees continues to shifted up from analysis down over the weekend. While the south end of the San Joaquin Valley is still favored with Merced County now showing percentages in the 30-50 percent range. There is a high likelihood of maintaining heat advisory criteria for the entire San Joaquin Valley throughout the week and into the weekend.

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 Wednesday with a new set of heat products later this week. Climate Prediction Center still 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 8 PM PDT Wednesday for CAZ337>339. Heat Advisory until 8 PM PDT Wednesday for CAZ301>317-319-321- 332-334>336.