textproduct: San Joaquin Valley

KEY MESSAGES

1. Moderate Heat Risk on Thursday.

2. Elevated Fire Weather Concerns across portions of the San Joaquin Valley and West Hills of the Coastal Range for increased winds and low humidity on Thursday.

3. Seasonally average weather returns this weekend. Next warm-up expected later next week.

DISCUSSION

Heat Dome making its eastward push as a disturbance moves into the Pacific Northwest. The disturbance will force the high pressure to move east and taking with it the heat and moisture. At this point, Central California will see stronger surface winds and a cool down of temperatures. The stronger onshore winds will also shift the moisture (monsoonal) east as heavy precipitation and higher humidity will now exist over the Great Basin (Desert Southwest) and Rockies. Probability of Exceedance (PoE) of reaching 105 degrees will stay below 10 percent through next Wednesday with a slight rise by Thursday. PoE of 100 degrees does take a downward turn through Saturday and slowly rises through the middle of next week. Therefore, will expect near seasonal normal temperature for a good portion of the period with a little uncertainty on the timing of the next heat wave.

Winds will be on the increase Today as the Pacific Northwest Disturbance provides some weather influence on Central California. Along with temperatures, Probability of surface winds reaching 25 mph or greater will have about a 50-80 percent chance of occurring. Those chances do drop-off on Friday with a 40-70 percent before wind speeds diminish as the disturbance mover further away and the ridge pattern rebuilds over the West.

Outside of the Sierra Nevada Crest, will expect dry conditions through the weekend with a return of the monsoon moisture early next week. Current guidance indicates a slight (less than 10 percent) probability for thunderstorms across the crest through the rest of the work week. Furthermore, without the abundant mid and upper level moisture observed in days past, any thunderstorms that do form are not favorable for severe weather impacts such as heavy rainfall and large hail. At this point, Probability of Measurable Precipitation above 20 percent is expected to the Mojave Desert by next Wednesday and spread further toward Central California later next week. Longer range ensemble analysis has the heat dome centered closer to the Mid-West as the associated flow pattern pushes the monsoon moisture back toward Central California late in the weekend. Climate Prediction Center (CPC) is indicating that the extended time frame of the 6 to 10 day period will remain on the warm side. Current CPC analysis has a 40-50 percent chance that temperatures will lean toward above normal conditions.

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 until 11 PM PDT this evening for CAZ305>307- 309>316-319-321.