textproduct: San Joaquin Valley

KEY MESSAGES

1. High pressure over the region will maintain temperatures near seasonal averages for the remainder of Central California today through Wednesday, with a warmup commencing Thursday.

2. Major Heat Risk developing Thursday for the Indian Wells Valley, Mojave Slopes and Desert, with an Extreme Heat Warning through next Monday.

3. Prolonged heat is expected to affect the SJ valley this weekend and a Heat Advisory or Extreme Heat Warning is likely.

4. Seasonably dry conditions to prevail through the week, with no monsoon moisture expected in the mountains. Along with well above normal temperatures, this will produce elevated fire weather concerns late this week into early next week.

DISCUSSION

Weak disturbance moving through the Northwest within the next 24 hours. This disturbance has introduced a strong westerly wind keeping the monsoon moisture across the Desert Southwest and well east of Central California. Another thing expected with the traveling disturbance is the retrogression of the High pressure area from the Mid-west back to the West Coast. Current thinking has the heat dome over the Desert Southwest on Thursday (including the Mojave Desert) and shifting further west on Friday. Therefore, a heat wave is about the start with some uncertainty on the extent and if it can make into the San Joaquin Valley.

Probability of Exceedance (PoE) of reaching 105 degrees are high and into the 70-90 percent range for the Mojave Desert. Moreover, PoE of reaching 110 degrees remains high for the Mojave Desert and will therefore add confidence toward the expected Extreme Heat Warning this weekend. Still on the fence on the Heat Advisory for the San Joaquin Valley as PoE of 105 degrees stays below 50 percent. Will continue to monitor the situation to see if an advisory will be warranted. Upper-air model analysis has the axis of the high pressure area over the West Coast this Saturday which look to the peak heating day of the heat wave event. Afterward, while PoE of 105 degrees do not drop off toward the middle part of next week, PoE percentage hold steady with minimal change through next Wednesday. Therefore, the heat, while not super hot, will continue for at least the next seven days. Furthermore, Probability of Thunder remains below 10 percent (also not existence) for the next seven days.

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 from 11 AM Thursday to 11 PM PDT Monday for CAZ337>339.