textproduct: San Joaquin Valley

KEY MESSAGES

1. Warming trend through the week into the weekend.

2. 5 to 15 percent chance of thunderstorms in the Sierra Nevada through Thursday.

3. Next best chance of rain for the San Joaquin Valley comes next week.

DISCUSSION

Relatively benign conditions have set up across central California with temperatures in the San Joauqin Valley near season averages. Weak moisture influences from a shortwave upper level trough brought isolated showers to the Sierra Nevada today, of which there will be additional chances through Thursday as a weak cut-off low pressure system tracks through southern California. Cyclonic flow around the low will bring moisture to the region which is likely to condense as it moves up the terrain. Chances for thunderstorms are five to ten percent for Wednesday and ten to fifteen percent for the high elevations from Yosemite National Park to Sequoia and Kings Canyon National Parks.

In the latter part of the week, a weak high pressure ridge is favored to build over central California, resulting in a warming trend across the region as well as lowering relative humidity values. On Friday, there is a 50 to 60 percent probability for afternoon temperatures to exceed 90 degrees in the western San Joaquin Valley, with these probabilities extending to the majority of the valley areas on Saturday. Probabilities for these temperatures are 70 to 80 percent for the valley portions of Kern County.

However, as the late weekend approaches, a pattern change will take hold as a stronger cut-off low pressure system slides southward along the Pacific coast. This system will be the next best chance for precipitation in the San Joaquin Valley and Sierra Foothills as warm, saturated air is forced northward from the tropical areas. Over a 48 hour period ending next Wednesday morning, there is a 40 to 50 percent probability for the valley areas to recieve measurable rainfall (>0.01"), increasing to 70 to 80 percent for the mountain areas. Over the same time frame, there is a 50 to 60 percent probability for more than one inch of snowfall for the mountain areas as snow levels are projected to be around 7,000 feet.

AVIATION

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

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

None.