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. Precipitation chances may return again by next weekend.

DISCUSSION

Heat Dome continues its eastward shift as noted on afternoon highs Today. While the south-end of the San Joaquin Valley saw minimal cooling from lingering heat, the entire valley will begin cooling on Monday. Yet, slight cooling will be observed on Monday (ahead of the next disturbance) with better cooling on Tuesday. The next disturbance will allow surface pressure gradients to tighten during the next 24 hours. However, ensembles place the KSFO-KLAS peak gradient around 8mb. This will result in breezy winds (especially over the wind favored locations) but, below advisory levels. In addition, disturbance will introduce dry air into the region which will limit convection and heighten fire weather concerns.

As we approach the mid-week period, ensemble surface temperature analysis indicate a sharp drop in values in the wake of the Pacific Northwest disturbance. Therefore, Probability of Exceedance (PoE) of reaching 100 degrees is almost non- existence, PoE of reaching 90 degrees across the San Joaquin Valley show the sharp drop occurring on Tuesday. At that point, ensemble surface analysis show probabilities of 90 degrees in the 60-80 percent range on Monday and dropping to less than 10 percent on Tuesday. Ensemble analysis show a rebound back to 90 degrees by Saturday and Sunday as probabilities reach near 20 percent.

Across the Eastern Pacific, satellite imagery and surface marine analysis is showing Tropical Storm Lowell, Hurricane Karina and Invest 95E (which is southwest of Acapulco). Lowell is already near Hawaii with Karina trending towards the Islands. Therefore, Integrated Water Vapor Transport show minimal effects over Central California from Lowell and Karina. Long term analysis does show a concern for Invest 95E. Even with the uncertainty of its track (95E), moisture flow pushing toward California and is trending toward entering the region during the weekend. In the meanwhile, ensemble thunderstorm analysis show minimal percentage values until Sunday when the surge of subtropical moisture overspreads the region.

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.