textproduct: San Joaquin Valley

KEY MESSAGES

1. Heat Advisory issued for the San Joaquin Valley, Sierra Foothills and West Side Hills along the Coastal Range.

2. High probability (70 to 80 percent) for triple digit highs in the San Joaquin Valley on Thursday.

3. Medium probability (30 to 50 percent) for measurable rainfall in the Sierra Nevada near Mount Whitney both Wednesday and Thursday.

4. Stronger winds expected to develop in the Mojave Desert Slopes later this week.

DISCUSSION

A small amount of moisture continuing to move through Southern and Central California is currently producing high level clouds that may last through the night and into the next few days as the post-tropical system Marie moves northwest. This moisture may also cause isolated thunderstorms along the highest portions of the Sierra Nevada as it runs into said range, though the chances for measureable precipitation is about 30-50% on Wednesday and 20 to 40% on Thursday, both days around Mt. Whitney. Along with that is a 5-15% chance for thunderstorm development both days.

At the same time, due to an incoming ridge, temperatures in the Valley are expected to reach triple digits by tomorrow afternoon and peak around 101 to 103 degrees on Thursday, while the Mojave Desert will likely see highs of 102 to 104 degrees on Wednesday, increasing to 106 degrees on Thursday. This combined with lows in the upper 60's and into the mid 70's in the Valley and into the upper 70's and approaching 80 degrees in the Desert, widespread Moderate Heat Risk with large areas of Major Heat Risk is expected both tomorrow and Thursday, which poses a risk to much of the population, especially those without proper cooling overnight. Due to these conditions, a Heat Advisory has been issued for the San Joaquin Valley, West Side Hills and Sierra Nevada foothills from tomorrow at 10 AM through 10 PM Thursday.

Thankfully, these temperatures are expected to be short lived as the ridge is pushed out of the southwest by an incoming trough from the Pacific Northwest, leading to a rapid cooldown to below normal highs and around normal lows. This trough will likely also cause strong winds across the Mojave Slopes when the pressure gradients become much stronger as it passes over Central California from Friday into Saturday. Current chance for 45 mph wind gusts along the Mojave SLopes are 50-70% on both of those days.

Looking into the long term forecast, the center of the trough mentioned before is expected to move east and leave behind a weaker trough by Monday next week. This would raise temperatures a couple degrees, but this pattern looks to hold for several days, leading to consistent near normal temperatures from Monday into the later week. This is reflected in the 6 to 10 day outlook from the Climate Prediction Center, as they have our CWA in likely near normal temperatures for that time period, though the 8 to 14 day outlook moves to leaning above normal for temps. Precipitation is similar in both outlooks at near to leaning above normal, though rainfall isn't expected after Friday into early next week.

AVIATION

VFR conditions expected 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

Heat Advisory from 10 AM Wednesday to 10 PM PDT Thursday for CAZ300>317-319-321.