textproduct: San Joaquin Valley

UPDATE

Updated Aviation Section.

KEY MESSAGES

1. Warm conditions continue today with temperatures 5-10 degrees above normal.

2. Moderate fire risk with minimum relative humidity below 20% in the foothills, Sierra Nevada and desert on Sunday.

3. High confidence in a pattern change early next week.

4. Temperatures well below average next week with moderate confidence of rain and high Sierra snow early Wednesday morning through Thursday.

DISCUSSION

Another warm day will take place on Sunday, although the chances for highs at or above 90 degrees in the Central Valley are relatively low (10-20 percent, except 40-50 percent towards the south end and along the adjacent higher terrain). Dry conditions once again prevail, but humidity will improve beginning Monday as noticeably cooler temperatures arrive.

Besides further cooling on Tuesday and the remainder of the week, the big story will be the chances for widespread precipitation on Wednesday into Thursday morning. Probabilities have risen to 70-80 percent chance of at least a tenth of an inch in the San Joaquin Valley. Amounts of 0.50 inch or greater are currently at a 60-70 percent chance for the Sierra Nevada. There is also a 70-80 percent chance for the desert and Sierra foothills for a tenth of an inch and a 30-40 percent chance for at least a half inch. There is also a slight chance of thunderstorms for much of the region. However, considerable model uncertainty remains regarding heavier amounts due to slow moving storms over the desert as mentioned in the previous discussion; confidence is low regarding this scenario. Around 3-6 inches of snow above 8,000 feet in the Sierra Nevada has a moderate chance of occurrence (including a 40-50 percent for at least 4 inches) from Yosemite to Sequoia NP. Temperatures will remain near 70 degrees from Wednesday onward, with the greatest chances on from Wednesday until Friday (45 to 55 percent chance to reach 70 degrees or lower). Another chance for precipitation occurs later next weekend. Confidence is high regarding the cooler temperatures to persist for much of next week and the following weekend. In addition, the CPC (Climate Prediction Center) mentions below average temperatures (near 40 percent chance) and above average precipitation (40-60 percent) for the 6-10 day and 8-14 day periods.

AVIATION

VFR conditions and light winds 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.