textproduct: San Joaquin Valley

UPDATE

Updated Aviation Section.

KEY MESSAGES

1. Minor Heat Risk through Tuesday as temperatures remain at or below seasonal normal values.

2. A warming trend in temperatures starts on Wednesday as the region will see the return of heat during the latter part of the period. Thursday looks to be the hottest day with a greater than 70% chance of a Moderate Heat Risk.

3. A disturbance will cross the region on Monday and Tuesday with a slight chance of showers and thunderstorms across the Sierra Nevada Monday afternoon.

DISCUSSION

The passage of a disturbance that brought cooler conditions and a slight increase in winds continues to push out as a high pressure ridge takes over. While winds have diminished, temperatures remain on the cooler side as another disturbance expected on Monday will hinder any significant warm-up. Furthermore, the disturbance on Monday will introduce a chance for mountain showers and thunderstorms, along with an increase in cloud cover over most of Central California. After its passage, ridging returns to the area as the current minor heat risk elevates to moderate heat risk levels later next week.

Taking a closer look, while the Probability of Exceedance (PoE) of reaching 90 degrees goes into the 70-80 percent range by Tuesday, the PoE of reaching 95 degrees does not break above 30 percent until next Wednesday. Therefore, confidence is high that a warming trend will occur and peak out on Thursday. At that point, PoE of reaching 100 degrees rises to above 50 percent for area in the San Joaquin Valley from Fresno County, southward.

In addition, ensemble analysis begin to increase the Probability of Thunder (PoT) across the Sierra Nevada on Monday. With an increase from near zero to above 10 percent from Sunday to Monday, respectfully, confidence grows toward the likelihood of afternoon mountain convection on Monday afternoon. Furthermore, the Probability of Measurable Precipitation for at least a tenth of an inch (0.10) climbs up to 30-50 percent on Monday as ensemble analysis targets the Sierra Nevada from Fresno to Tulare Counties for the period in question.

AVIATION

MVFR with local IFR conditions will exist across the Sierra Nevada and adjacent foothills as smoke from the Dome Fire in Yosemite continues through 08Z Sunday. After 08Z, MVFR visibility in the vicinity of the Dome Fire. Otherwise, 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.