textproduct: San Joaquin Valley

KEY MESSAGES

1. Wind Advisories and a Lake Wind Advisory in effect through Monday for the Kern River Valley, Indian Wells Valley, and Mojave Desert. Wind Advisory for the Mojave Desert Slopes in effect through Tuesday morning.

2. 15 to 35 percent chance of thunderstorms over the Sierra Nevada Monday, decreasing to 10 to 15 percent on Tuesday. 5 to 15% chance across the Valley and into the foothills during this period.

3. Cooler, unsettled weather until Tuesday with snow above 7,000 feet in the Sierra Nevada.

4. Warm up anticipated late this weekend into early next week with high confidence for at least Moderate Heat Risk in the valley areas.

DISCUSSION

A cutoff low pressure system is currently positioned over the central California coast resulting in cool, cloudy conditions over the Central Valley and Sierra Nevada this morning. Due to the low's location, winds over the region are flowing from the east-southeast. Ample moisture associated with the system is moving across warmer ground in Mono County, developing a few scattered showers which are expected to track into the central Sierra Nevada, mainly around Yosemite NP. As afternoon temperatures warm over this area, these showers have the potential to strengthen into thunderstorms with probabilities for this area sitting around 25 to 30 percent today. A few of these showers may track into the surrounding foothills, and as such there is around a 15 to 20 percent probability, though chances diminish considerably into the valley areas. Snow levels around 7,000 feet with this system will bring additional snowfall accumulations to these areas, albeit with 72 hour totals only up to an inch at these elevations; the highest elevations of the Sierra an expect to see an additional three to five inches.

This system will continue to bring stronger winds to the desert areas as well as the mountainous areas of Kern County today. Through 11 PM tonight, there is an 80 to 90 percent probability for maximum wind gusts to exceed 40 mph in the Mojave Slopes including Mojave, Jawbone, and Walker Pass, as well as the open desert areas including Edwards AFB, California City, and Randsburg. A Wind Advisory is in effect for these locations through 11 PM tonight (Desert) and through 8 AM tomorrow (Slopes). Additionally, a Lake Wind Advisory remains in effect for Lake Isabella until 11 PM tonight due to wind gusts up to 40 mph as well.

This low pressure system will gradually track into southern California and Arizona tomorrow before being absorbed by a longwave trough moving through the eastern half of the country on Wednesday. At that time and trough the remainder of the week, a high pressure ridge will build in over central California and strengthen into the weekend and early next week. A warming trend will take hold as a result, with afternoon highs near season averages on Wednesday, but warming close to ten degrees above average on Saturday. The trend will continue into next Monday, at which point highs will be approaching twenty degrees above average, in large part due to the center of the ridge moving directly over north central California and western Nevada. For Monday, there is a 70 to 80 percent probability for maximum temperatures to exceed 100 degrees in the San Joaquin Valley, leading to Moderate Heat Risk expected across the area with a few isolated pockets of Major Heat Risk.

AVIATION

VFR conditions will prevail for the next 24 hours over Central California, except in and near thunderstorms, where MVFR and IFR conditions can be expected. Surface Wind Gusts G35KT expected across the Tehachapi Range and Mojave Desert through 12Z Tuesday.

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 8 AM PDT Tuesday for CAZ338. Lake Wind Advisory until 11 PM PDT this evening for CAZ332. Wind Advisory until 11 PM PDT this evening for CAZ337-339.