textproduct: San Joaquin Valley

KEY MESSAGES

1. Early season heat arrives 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 highs were similar to yesterday's high temperatures, and the warmest locations in the San Joaquin Valley reached into the lower 90s. Highs in the Kern County desert were a bit higher today; a high of 97 degrees was recorded at China Lake NAWS. Sunday's highs are on track to reach the mid 90s to near 100 degrees in the valley and desert. More widespread triple digit heat also remains on track to occur on Monday and Tuesday, with high probabilities of these readings in much of the Central Valley and thermal belt locations. The Heat Advisory will remain in effect for the SJ Valley, Coastal Ranges, and the Lake Isabella/Kern River Valley areas. Low daytime humidity and afternoon breezes will accompany the warm temperatures, which will bring an elevated threat of grass and brush fires to much of the region until at least early next week. Any fires that develop have the potential to spread rapidly. Also, remember to practice cold water safety if venturing into the waterways and lakes!

A slight chance for afternoon and evening thunderstorms will occur on Tuesday along the Sierra Nevada crest as the low pressure trough approaches. Otherwise, dry conditions prevail. More noticeable cooling arrives on Wednesday throughout the region, although high temperatures remain above average. Similar temperatures will continue until late next week and the following weekend, including those much like today's highs.

Latest CPC outlooks continue to show a moderate to high probability of above average temperatures for the 6-10 day and 8-14 day periods. However, a slight tilt in the odds (33-40 percent chance) for below average precipitation is now shown for the 6-10 day outlook, while the 8-14 day out look shows a return to above average precipitation with also a slight tilt in the odds.

AVIATION

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

FIRE WEATHER

Warming out of shade temperatures through this weekend and early next week will result in lowering relative humidities across the region. Minimum RHs in the Mojave desert will fall below to 5 to 10 percent from Sunday through Tuesday. RHs will fall to or below 15 percent in the San Joaquin Valley and Sierra Nevada again Sunday afternoon and continue at these values until Tuesday, while the mountains in southern Kern County fall to 10 percent or less. An elevated risk for grass fires and brush fires will continue in the Central Valley, Coastal Ranges, Sierra Nevada foothills, as well as the Kern County mountains and desert. 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. Upsloping winds from the southeast along the eastern Sierra can help to further dry fuels, especially in the portion of the range in southern Tulare County. New fire starts may also spread more quickly with increased gusts along the southern Sierra.

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

Heat Advisory from 11 AM Monday to 8 PM PDT Tuesday for CAZ300>317-319-321-332.