textproduct: San Joaquin Valley

KEY MESSAGES

1. Red Flag Warning in Effect through Saturday 11 PM for the following Fire Weather Zones: Indian Wells Valley, Kern County Desert, and Lake Isabella.

2. Dry and windy conditions create significant fire risk this weekend, particularly in Eastern Kern and Southeastern Tulare Counties.

3. Cool down through the weekend will bring below normal temperatures.

4. Practice safety around lakes, rivers and streams, as water is still running cold.

DISCUSSION

A deep low pressure system is located over the Pacific Northwest this morning, with a strong pressure gradient extending southward across much of California, with a 200 to 250 meter drop between the south and northern portion of the state. This strong pressure gradient has resulted in a upper level jet tracking over central California with air originating from cooler regions in the Gulf of Alaska. As a consequence, temperatures are expected to gradually fall near 10 degrees below averages for the weekend; there is less than a 20 percent probability for temperatures to warm above 90 degrees in the San Joaquin Valley both days. Meanwhile, the stronger winds will continue downsloping along the Tehachapi Mountain Range into the Kern County Desert, leading to a Wind Advisory that remains in effect until 5 AM Sunday. In this area, there is an 80 to 90 percent probability for maximum gusts to exceed 50 mph.

As we progress through the rest of the weekend and into early next week, the center of the aforementioned trough will track into the northern Rockies, but remain extended over California. The continued northwesterly flow will keep temepratures near average, but drier air will gradually move in with minRH values near 20 percent in the San Joaquin Valley starting Monday and values between 10 and 15 percent in the Kern Desert.

Ensemble cluster analysis expresses favorability for a continuation of this troughing pattern through the upcoming week, albeit not as strong as this weekend's system. As a result, temperatures across central California are expected to remain below season averages through next Saturday. Probabilities to exceed 95 degrees are less than 20 percent each day until next weekend for the San Joaquin Valley.

AVIATION

VFR conditions expected across the area for the next 24 hours. 60-70% probability for surface wind gusts reaching 35kts across the Sierra Nevada Crest through 00Z Sun. 80-90% probability or surface wind gusts to reach 45kts for the Mojave Desert through 12Z Sun.

FIRE WEATHER

Red Flag Warning continues for the Kern County Desert and Lake Isabella area through 11 PM tonight due to strong winds and low, but improving, relative humidity. For the desert areas, there remains an 80 to 90 percent probability for maximum wind gusts to exceed 50 mph today with expected minimum relative humidity between 12 and 20 percent. At Lake Isabella, there is a 70 to 80 percent probability for wind gusts greater than 30 mph this afternoon, but with minRH values at 30 to 35 percent. Winds will gradually diminish into early next week as upper level winds weaken. However, flow will continue from the northwest due to an extended troughing pattern which will continue to result in lower RH values across the region. RHs in the San Joaquin Valley are expected around 20 percent through midweek, with 10 to 15 percent in the Kern Desert.

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

Red Flag Warning until 11 PM PDT this evening for CAZ298-299- 595. Wind Advisory until 5 AM PDT Sunday for CAZ337-339.