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

A ridge of high pressure continues to dominate in the West but a shortwave trough brought a slight tumble on Tuesday in temperatures. However, the ridge of high pressure begins to move east on Wednesday as the shortwave slides away to the Northeast. In the Valley, there is a 40 to 75 percent chance of triple digits on Wednesday.

As the ridge strengthens on Thursday into the weekend, temperatures will soar to above average. The Mojave Slopes and Desert are under an Extreme Heat Warning through next Monday as there is a 10 to 45 percent chance on Friday and a 45 to 85 percent chance on Saturday and Sunday of 110 degrees in the Desert. In the Valley, we are looking at a 10 to 25 percent chance of highs of at least 105 degrees before increasing to 25 to 40 percent on Sunday. These probabilities have lowered over the past few NBM model runs. However, a Heat Advisory remains possible for Saturday and Sunday in the Valley. The CPC continues to signal above average temperatures with a 60 to 70 percent chance in the 6-10 day outlook and a 50 to 60 percent chance in the 8-14 day outlook.

AVIATION

VFR conditions will prevail for the next 24 hours.

FIRE WEATHER

The warmup into this weekend brings some fire concerns due to well above average temperatures and lowering minRH values. The mean minRH values in the Mojave Slopes and Desert will persist in the single digits into next week. The foothills will drop slightly from the high teens and low 20s to the mid to upper teens. The winds will remain mostly diurnal and light in the Valley and foothills but gusty along the Sierra crest and the Mojave Slopes especially in the afternoon.

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.