textproduct: San Joaquin Valley

KEY MESSAGES

1. Below average temperatures continue for central California through the weekend before a warming trend next week.

2. Moisture over southern California brings a 50 to 60 percent probability of precipitation for the Kern County Desert Sunday.

3. Strong winds expected over the Sierra Nevada crest Saturday and Sunday.

4. Medium probability (40 to 50 percent) for Moderate Heat Risk in the San Joaquin Valley Thursday.

5. Additional chances Wednesday for rainfall in the Sierra Nevada.

DISCUSSION

A cut-off low pressure trough remains firmly centered over the Pacific Northwest, as has been the case for the previous few days. The trough is experiencing a weak deepening southward, forcing the prevailing flow over central California from the west to the south. The result will be warmer temperatures this afternoon across the region by a few degrees; while much of the Central Valley failed to reach 85 degrees yesterday, there is an 80 to 90 percent probability today. Similar probabilities are expected tomorrow as there will be little chance in the overall synoptic pattern to the north of the region; however, to the south, outflowing moisture from Hurricane Marie will push through southern California.

Most of this moisture will remain to the south of our CWA, though light rainfall is expected in the far eastern portions of the Kern County Desert. Between 5 AM Sunday and 5 AM Monday, there is a 60 to 70 percent probability for rainfall to exceed 0.01" for the likes of Edwards AFB, Boron, and Johannesburg, and between 40 and 50 percent for Mojave, Frazier Park, Tehachapi, and Ridgecrest. Probabilities for greater than 0.1" for the first of these locations is at 40 to 50 percent, and 20 to 30 percent for the latter. Any precipitation occurring Sunday and Monday is expected to be limited to the Kern Mountains and Desert, as there is less than a 10 percent probability for 0.01" for Bakersfield northward.

The aforementioned trough will result in gusty winds over the Sierra Nevada crests this afternoon and Sunday as mid-levels winds interact with the heights of the local terrain. For both Saturday and Sunday, there is a 60 to 70 percent probability for maximum gusts to exceed 45 mph above 10,000 feet, with the greatest of these chances in Madera and Fresno Counties uphill from Mammoth Lakes.

As we enter the new week, the trough will gradually begin to move eastward, weakening its influence over central California and creating a brief return to zonal flow. Between Tuesday and Wednesday, a second weak trough will develop in the wake of the current one, extending just north of Hurricane Marie's forecast track. The current consensus is the trough and tropical system will phase together, allowing another push of moisture to arrive from the south. However, recent model runs have indicated a high pressure ridge will build in from the east at the same time. Depending on the strength and positioning of the ridge, this moisture may ultimately remain offshore. Though, as it stands, the high-end scenario from the NBM (1 in 10 chance of occurrence) shows just under an inch of rainfall for the Sierra Nevada between 5 PM Tue and 5 PM Wed, and less than 0.1" for the San Joaquin Valley.

AVIATION

VFR conditions expected for the next 24 hours.

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.