textproduct: San Joaquin Valley

KEY MESSAGES

1. Heat Advisory remains in effect for the San Joaquin and Kern River Valley until 11 PM Tuesday.

2. Widespread Moderate Heat Risk, including triple-digit heat, in the lower elevations through Wednesday. Some pockets of Major Heat Risk, particularly near urban areas.

3. Hot and dry conditions will create increased fire risk across the region this week.

4, 15-25% probability for thunderstorms in the Sierra Nevada the next few days, which may include dry lightning.

5. Practice safety around lakes, rivers, and streams, as water is still running cold.

DISCUSSION

Flat high pressure ridge still holing off the Pacific Coast as Central Californias Heat Wave continues this Tuesday. While ensemble upper-air analysis does show the flatness due to zonal flow over the Pacific Northwest and British Columbia, the heat remains as triple-digits will be seen again this afternoon. Yet, the pattern is changing as the ridge of high pressure retrogrades further into the Pacific and an area of weakness under-cuts the ridge. This area of weakness will cross the region later this week as mountain convection go into an increasing trend with a near 30 percent change of thunder near Yosemite by Thursday. While convection will be on the up-tick, the San Joaquin Valley will see some relief from the heat going into next weekend.

Current ensemble surface temperature analysis has Probability of Exceedance (PoE) of San Joaquin Valley (SJV) temperatures reaching 100 deg in the 60 to 90 percent range with higher percentage values over the Kern County portion of the SJV and near 30-40 percent for Merced County. These percentages the then see a downward trend going into Wednesday and Thursday. By Friday, will expect afternoon high temperatures at near seasonal normal values as PoE of reaching 95 deg remains below 10 percent and PoE of 90 deg hits the 30-60 percent range (with higher percentage over Kern County). Conditions will remain static during the weekend with the high pressure ridge axis shift east and over the West Coast by Tuesday. Therefore, the area will return to near triple-digits early next week.

Precipitation-wise, will see isolated convection over the Sierra Crest today and Wednesday. With better lift on Thursday from the passage of the weak disturbance (weakness), will see a rising trend to near 30 percent along the Sierra Crest near Yosemite on Thursday. While percentage do drop slightly on Friday, will expect little change in coverage on Friday before we hit the back end (wake) of the disturbance on Saturday. At that point moving forward, will see a decreasing trend in Convection through early next week.

AVIATION

VFR conditions expected in the San Joaquin Valley 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 CAZ300>321-332.