textproduct: San Joaquin Valley

KEY MESSAGES

1. Minor Heat Risk through the weekend as temperatures cool to early fall normals.

2. Low pressure trough approaches California Sunday, bringing cooler temperatures and a possibility for precipitation along the Sierra Nevada moutains.

3. Low but notable chances (10-12%) for thunderstorms across the Sierra Nevada Monday.

DISCUSSION

Central California will be under the influence of a disturbance currently moving through the Pacific Northwest. While no precipitation will be observed from this passage, due to the distance the disturbance, it will influence our temperatures. This disturbance will allow for an increase in the onshore over the district for the next day (Tonight and Saturday). Again, due to the distance of the disturbance to Central California, the cool-down will be minimal as Probability of Exceedance (PoE) of reaching 90 degrees will range from 70-90 percent of Saturday. In addition, PoE of reaching 35 mph across the Mojave Desert (Wind favored spot) will only rise to around 30 percent on Saturday as some locations will see breezy winds Saturday Afternoon.

This disturbance will precede a second disturbance expected to arrive during the day on Sunday. The second disturbance is expected to enter California and begin affecting Central California during the day. While the center of the disturbance will reside over Sacramento, enough energy will push into Central California and provide the district will a significant cool-down and strong winds. By Sunday, PoE of reaching 90 degrees drops below 30 percent (outside of Bakersfield) with most afternoon high values in the upper 80s. At the same time, Wind Gusts PoE of reaching above 35 mph increases over the favored spots as places like Mojave and Ridgecrest are expected to have percentages in the 50-70 percent range.

Monday will be a different story as moisture from Hurricanes Polo and Odalys surge into the Baja California and Desert Southwest area. The interaction between the second disturbance and the hurricanes will limit the amount of moisture able to enter the Central California area. Currently longer-term analysis does show wrap-around moisture able to push northwest and into the the Sierra Nevada as the mountains will see an increase in moisture. Again, while limited, ensemble precipitation analysis does placed a chance of showers (and thunderstorms) on Monday. At the same time, PoE of reaching 90 degrees bottoms out at near zero as the cooler air overspreads much of the district. Therefore, with less of a temperature gradient from the valley to the desert, winds are also expected to diminish starting on Monday.

Ensemble model consensus has the disturbance east of the region by Tuesday as ridging returns to the West Coast. A warming trend with dry conditions will enter on Tuesday and persist for much of the period. Climate Prediction Center is placing Central California in the Likely Above Normal Temperatures categories for both 6 to 10 Day and 8 to 14 Day periods. At the same time, Precipitation is expected to remain at Near Normal values.

AVIATION

VFR conditions will prevail 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.