textproduct: San Joaquin Valley

KEY MESSAGES

1. Changing weather patterns bring cooler weather and the next regional chances for rain this week.

2. Potential for thunderstorms across the area again tomorrow, ranging from 5 to 10% in the San Joaquin Valley up to 40% along the Sierra Nevada crest.

3. Threat of damaging wind from strong thunderstorms along the San Joaquin Valley and Sierra Nevada.

DISCUSSION

A trough off the coast of California will be responsible for a noticeable cooldown across the region through this week as highs dip below normal for the first time in several weeks. This will coincide with a marked increase in thunderstorm chances and activity across the Sierra Nevada mountains and may reach into the San Joaquin Valley as seen earlier this morning. This activity may also be increased due to a small area of stronger vorticity that is modeled to move through Central California ahead of the trough. Current chances for this activity is around 30-40% along the Sierra Nevada crest and about 5-10% in the Valley, mainly from 11am through 8pm tomorrow. There is also a 10% chance for isolated dry thunderstorms in the Sierras from Madera County northwards, which may produce little wetting rain with frequent lightning, increasing the chance for new fire starts.

From Friday onwards, thunderstorm chances drop off a cliff and will remain less than 10% through the rest of this week as the trough broadens and loses its energy through that time. Temperatures will also remain below normal through Friday before a small warm up of a few degrees takes place over the weekend due to the broadened trough, while still remaining a few degrees below normal. Looking to the long term, temperatures may become above normal once again by the weekend after next, as the Climate Prediction Center has our area under leaning above normal temperatures by the Day 8 through 14 outlook, along with a leaning above normal for precipitation, suggesting another monsoonal moisture push is possible during that time period.

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.