textproduct: San Joaquin Valley

KEY MESSAGES

1. Red Flag Warning issued for the Sierra Nevada above 4000 feet due to high winds and low relative humidity from Thursday morning through Friday evening.

2. Wind Advisory has been issued for the Mojave Desert zones from Thursday AM through Friday night with wind gusting up to 55mph.

3. A warming trend continues through the weekend before a cooldown next week.

4. A pattern change may be upon us early next week as a disturbance crosses the West and introduces unsettled conditions.

DISCUSSION

Welcome to this morning's Forecast Discussion, our reader's favorite time of the day!

Today and Friday will be troublesome times for our mountain and desert communities. Strong high pressure (with 500 millibar heights above the 90th percentile climate record for today) has set up over Northern California and will remain near stationary through Friday afternoon. Meanwhile, a weak area of low pressure centered over the tri-point of AZ, CA, and Baja California is expected to deepen and slide southwest-ward off the coast tonight. Cutting to the chase, this will bring strong winds from the east across our region's mountains and high desert. More information on wind products and fire danger will presented in the Fire Weather section of the discussion.

Unfortunately, with strong high pressure also comes warmer temperatures. Across the San Joaquin Valley, temperatures will reach about 10 degrees above average Friday and Saturday. But while afternoon highs in the low 90s are expected, good overnight recovery cooling to the mid-50s to low-60s will limit any potential heat illness risk just to those very sensitive to heat. By the start of the work week, high pressure is expected to weaken, move eastward, and quickly transition back to pleasant, fall- like temperatures.

Along with quickly transitioning back to more typical fall weather, figurative and literal storm clouds return to California some time next week as a shortwave trough crosses into the area from the Pacific Ocean. The expected, 50/50 scenario according to this morning's run of the National Blend of Models (NBM) places light rain of a tenth to quarter inch in the Sierra Nevada Tuesday through Thursday. Wetter, more aggressive scenarios with a less than 50 percent chance of occuring also show light rain between a trace to quarter inch for the San Joaquin Valley. But as this event is 5-7 days ahead, specifics are yet to come.

AVIATION

VFR conditions will prevail for the next 24 hours.

FIRE WEATHER

Red Flag Warning in effect until 10 PM Friday evening for the Sierra Nevada, Tehachapi, and San Emigdio mountains above 4,000 feet due to strong winds from the east and low humidity. Confidence for easterly gusts exceeding 40 MPH is highest (70-90 percent chance) tonight into Friday morning, though isolated areas will experience gusts this fast through the entire warned period. Minimum relative humidity today and Friday expected between 15-25 percent in the warned areas, with dryer areas as low as 10 percent.

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

Wind Advisory until 10 PM PDT Friday for CAZ337>339.

Red Flag Warning until 10 PM PDT Friday for CAZ592>597.