textproduct: San Joaquin Valley

KEY MESSAGES

1. 5-15% chance of thunderstorms across the Sierra Nevada today and through the rest of the week.

2. Above average temperatures across the CWA on Friday and Saturday

3. A closed-low enters our area next week, with the best probability for weather impacts on Tuesday and Wednesday.

DISCUSSION

As with the previous few days, a cutoff low is slowly approaching southern California which will fully push through the region on Thursday. Moisture from the cutoff low combining with influence from a shortwave trough passing from the north will bring chances for thunderstorms along the central and southern Sierra Nevada tomorrow afternoon; chances stand at 10 to 15 percent for these areas. For Friday, a high pressure ridge is expected to build in with a 50 to 60 percent probability for afternoon temperatures to rise above 90 degrees in the western San Joaquin Valley. While there are similar probabilities in the south valley areas on Saturday, they are not as widespread through the valley as in previous day's model runs. This is mainly due to ensemble analysis placing the upcoming stronger cutoff low closer to central California earlier and beginning late Saturday.

Similar to previous cutoff low pressure systems that have moved through the region in the last month, this will be the areas next best opportunity to receive precipitation. Though for now, the precipitation appears mainly confined to the Sierra Nevada and portions of the surrounding foothills. Between Sunday and Monday, there is a 30 to 40 percent probability for more than one-tenth inch of precipitation over the central Sierra Nevada. Snow levels are projected between 7,000 and 8,000 feet, with a 60 to 70 percent probability for one inch or more of snowfall above these levels. However, there remains some uncertainty on these levels as cutoff low systems are difficulty to pinpoint exact location and timing in this time frame. Potential additional impacts from the upcoming system also include thunderstorm chances at 15 to 20 percent on Sunday and strong winds along the Sierra Crest and in the Mojave Desert.

AVIATION

VFR conditions will prevail for the next 24 hours over Central California.

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.