textproduct: San Joaquin Valley

KEY MESSAGES

1. Below average temperatures expected for the next several days.

2. A trough moving South along the Pacific Northwest is expected to join forces with a low pressure system off the SoCal coast, potentially bringing rain on Halloween weekend.

DISCUSSION

Some higher clouds were observed Today as temperatures continue their cooling trend. Will expect below to near-seasonal temperatures as the cooling trend will be exist through early next week. Probability of Exceedance of reaching 70 degrees remains low ahead and during the next storm this weekend. Upper- air moisture analysis is showing an increasing trend in water vapor. Therefore, while minimal lift will be observed over the San Joaquin Valley, oro-graphic lift will allow for isolated afternoon shower over the higher terrain on Thursday and Friday. Furthermore, the limited intrusion of moisture will allow for the continuation of mist (lower surface visibility) across the San Joaquin Valley before unsettled conditions during the weekend.

Ensemble models continue to show strong consensus for a significant storm developing off the Pacific Northwest coast on Saturday, bringing another round of precipitation to Central California starting late Saturday into early Sunday morning. The heaviest precipitation is expected later in the day on Sunday. While confidence in precipitation is high, model variability remains regarding exact accumulation totals due to a split flow weather pattern. Current guidance indicates:

* 48-Hour Probability of Precipitation (Late Saturday Early Monday): 25-45% chance of receiving 0.50 of an inch across the Sierra Nevada. * 48-Hour Snow Probabilities (Late Saturday Early Monday): 20-40% chance of receiving 4 inches across the Sierra Nevada above 7,000 feet. * 50th/Mean Percentile: Precipitation is very likely across the region this weekend. * 90th Percentile: (Worst-Cast Scenario): Up to 2 inches of liquidequivalent (rain/snow) across Central California.

We will continue to monitor and evaluate the potential for heavy rainfall. Current guidance from the Weather Prediction Center is indicating a Marginal Risk (5 percent) probability of excessive rainfall leading to flash flooding on Saturday and across Kern County and a small portion of Tulare County.

AVIATION

There is a potential for visibility to be slightly reduced over KBFL early tomorrow morning resulting in MVFR conditions. Otherwise, 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.