textproduct: San Joaquin Valley

UPDATE

Updated Aviation Section.

KEY MESSAGES

1. Early season heat arrive early next week with expected temperatures rising to triple-digit values Monday and Tuesday in the San Joaquin Valley.

2. Moderate Heat Risk expected for the valley areas, with a medium chance for Major Heat Risk.

3. Practice safety around area lakes, rivers, and streams as waters are running cold.

DISCUSSION

Today's high temperatures reached into the mid to upper 80's in the San Joaquin Valley to the 90's in the Kern County desert. Slightly warmer high temperatures will take place on Friday. The warming trend continues until early next week with a high probability (85-95 percent) of triple digit heat in the Central Valley on Monday and Tuesday. Overnight temperature recoveries will not be great in many locations during this period, especially in the larger cities and thermal belts in the lower Sierra foothills and over the coastal ranges, where low temperatures struggle to fall below the mid to upper 60s. Unfortunately, the warming trend will come with low humidity coupled with breezy conditions and will bring a moderate risk of wildfires in the Kern County desert and Mojave Desert slopes. A large wildfire has already developed southwest of Ridgecrest in the El Paso Mountains and continues to burn at this time.

A lowering trend in temperatures occurs during the middle of next week. However, highs will remain at least ten degrees above seasonal averages. The probability of a high at least 95 degrees falls to 30-40 percent in the Central Valley by Wednesday of next week.

Latest CPC outlooks show continued high probabilities of above average temperatures, with near to above average (although a slight tilt in the odds towards the above average category) precipitation in both the 6-10 day and 8-14 day outlooks.

AVIATION

VFR conditions will prevail for the next 24 hours over Central California.

FIRE WEATHER

Warming temperatures through this weekend and early next week will result in lowering relative humidities across the region. Beginning Friday, minimum RHs in the Mojave desert will fall below 20 percent, and below 15 percent on Saturday. For Sunday through Tuesday, minRHs are expected between 5 and 10 percent in this area. RHs will fall below 20 percent in the San Joaquin Valley and Sierra Nevada Friday afternoon and continue at these values into the weekend. RHs at 15 percent or less are expected for these areas on Monday and Tuesday, with the Tehachapi Range and southern Kern Mountains at or below 10 percent. A downtrend in 100- and 1000-hr dead fuel moistures is anticipated with this warming trend, however both parameters are expected to remain above critical thresholds. Additionally, subsidence from the high pressure ridge will keep winds relatively light across the region.

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

None.