textproduct: San Joaquin Valley

KEY MESSAGES

1. High confidence in a change in the weather pattern over the next several days with below average temperatures likely after today and precipitation mid-week.

2. This is likely to be the first wetting rainfall in the Central Valley this fall with a 75-85% chance of at least a quarter inch of rain in 24 hours by around mid-day Thursday.

3. Snowfall is likely above 8,000 feet in elevation with a 60-70% chance of at least 4 inches of snow (probabilities increase further at higher elevations).

DISCUSSION

Today's highs were in the upper 70s to mid 80s at the warmest locations, including in the Central Valley and Mojave Desert portions of eastern Kern County. While maximum temperatures were around five degrees lower than yesterday's, highs remained several degrees above seasonal averages today, mainly from Fresno southward. Expect temperatures to continue on the downward trend on Tuesday and even more on Wednesday when highs reach below average. Precipitation chances begin late Tuesday in the Sierra Nevada and spread to much of the forecast area by Wednesday. The bulk of the precipitation is now for Wednesday evening until Thursday morning, although additional showers will develop on Thursday afternoon. A slight chance of thunderstorms exists for both Wednesday and Thursday, mainly in the afternoons. In terms of precipitation amounts, we're seeing a high probability (75-85% chance) of at least 0.25 inch for the San Joaquin Valley on Wednesday into Thursday. There is a 70-80 percent chance for at least 0.50 inch of precipitation for the Sierra Nevada and foothills for a 24 hour period ending Thursday afternoon. As for snowfall, at least a 60-70 percent chance for at least 4 inches of snow is shown for the higher elevations of the Sierra Nevada, mainly above 8,000 feet. The heaviest snow amounts will occur above 10,000 feet; the latest Winter Storm Severity Index from the Weather Prediction Center shows minor to moderate impacts for portions of the Sierra crest due to snow loading.

From Friday onward, cooler temperatures prevail (highs mainly in the 70s in the lower elevations), although precipitation is no longer forecast through early next week. Nonetheless, the latest outlooks from the Climate Prediction Center continue to show the odds tilted towards above average precipitation out to 8-14 days. Temperatures show a tilt towards above average (40-50% chance) for the 6-10 day period, but revert to below average (similar probability) on the 8-14 day outlook.

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.