textproduct: San Joaquin Valley

KEY MESSAGES

1. Temperatures will be normal to slightly below normal through the weekend before below average by the middle of next week.

2. Remaining moisture over the region bring a 5-15% chance of thunderstorms from the foothills to the Sierra Nevada Crest this afternoon.

3. Precipitation chances return again in the middle of next week.

DISCUSSION

Heat Dome shifting east as the district will now see afternoon highs in the 90s for several days. A broad Trough Pattern over the West Coast forcing the heat over the Mid-West will persist for most of the week with pieces of energy flowing through it. The next piece will push through the area on Monday with very limited moisture. Therefore, the next disturbance will introduce a cooling trend in temperatures with limited precipitation over the Sierra Crest. This weather pattern is expected to remain over the West Coast through at least the end of the week.

While Probability of Exceedance (PoE) of reaching 100 degrees is almost non-existence, PoE of reaching 90 degrees across the San Joaquin Valley show a sharp drop from this weekend through mid-week. Ensemble surface analysis show probabilities of 90 degrees dropping to 10 to 35 percent from Tuesday through Thursday for most of the Valley. Therefore, confidence is high at widespread temperatures in the 80s will be observed around the mid-week period.

Across the Eastern Pacific, satellite imagery and surface marine analysis is showing Tropical Storm Karina some 1200 miles south of Southern California. While Karina is expected to drift northwest for several days (Wednesday) some moisture will be pulled toward California and transported to Central California. This prognosis will lead toward a 5 to 15 percent chance of measurable precipitation (accumulation) between Wednesday and next weekend for a large majority of the district. With the uncertainty in the influx and trajectory of the moisture, ensemble Thunderstorm probabilities will remain very this far in advance.

AVIATION

VFR conditions prevailing 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.