textproduct: San Joaquin Valley

KEY MESSAGES

1. Heat Advisory issued for the San Joaquin Valley and for Lake Isabella valid from 11 AM Monday, May 11th through 8 PM Tuesday, May 12th.

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

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

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

DISCUSSION

The warming trend continues, as high pressure builds over our forecast area. Today's highs were a few degrees warmer than yesterday's. Further warming will continue this weekend into early next week. There remains a moderate to high probability (55-65 percent) for widespread triple digit heat across the San Joaquin Valley into the Kern County desert on both Monday and Tuesday. Low temperatures will also remain in the mid to upper 60's in the largest cities in the SJ Valley and the typical thermal belts of the Sierra Nevada foothills, lower Tehachapi mountains, the coastal ranges, as well as the Kern County desert. Elsewhere in the lower elevations, low temperatures will generally be pleasant. Dry conditions will prevail over this weekend into early next week. By Tuesday, there is a slight (10-15 percent) chance for thunderstorms over the higher elevations of the Sierra Nevada as a low pressure system approaches the West Coast. Otherwise, expect winds to once again pick up over the Sierra Nevada crest and into the Kern County desert. In addition, humidity will continue to lower until early next week in the desert and the thermal belts in the foothills and coastal ranges each day as we heat up, and overnight recovery will worsen.

Noticeably cooler temperatures will take place by the middle of next week, but highs remain above seasonal averages with temperatures in the upper 80's to near 90 degrees in the warmest locations. Daytime humidity will remain low in these locations through much of next week, although overnight recovery will improve.

Latest CPC outlooks show continued above average temperatures with a slight tilt in the odds towards above average precipitation at both the 6-10 day and 8-14 day periods.

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. Minimum RHs in the Mojave desert will fall below 15 percent on Saturday. For Sunday through Tuesday, minRHs are expected between 5 and 10 percent in this area. RHs will fall to or 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. 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.