textproduct: San Joaquin Valley

KEY MESSAGES

1. Triple digit heat continues for San Joaquin Valley and Mojave Desert. 50 to 60 percent for Major Heat Risk in the Southern San Joaquin Valley at the start of this week. Heat Advisory issued valid Monday through Wednesday

2. A 5 to 15 percent probability for extreme heat risk in the Mojave Desert toward the end of the week and starting September. Extreme Heat Warning issued valid Monday through Wednesday.

DISCUSSION

Little change in the current synoptic pattern is expected as we enter a new week. A ridge of high pressure is currently situated over the Four Corners region of the desert southwest which will continue to keep the warmer, above average temperatures present across much of Central California. Each day through at least Wednesday, there is a 90 to 100 percent probability for temperatures to exceed 100 degrees in the southern San Joaquin Valley, mainly from Fresno southward. For the north valley areas, there is a 50 to 60 percent probability. Meanwhile in the south valley, there is an 80 to 90 percent probability for overnight lows to exceed 70 degrees, primarily in the foothill areas where the thermal belt is at its strongest and in the urban areas where the heat island effect will take hold. Due to both of these factors, widespread Moderate Heat Risk is expected across the valley, with some areas of Major Heat Risk. A Heat Advisory has been issued for the southern San Joaquin Valley valid from Monday through Wednesday evening.

Over the same time frame, temepratures in the Mojave Desert have an 80 to 90 percent probability to exceed 105 degrees in the afternoons and a 70 to 80 percent probability for overnight lows to exceed 75 degrees for the communities of Inyokern, Mojave, and Ridgecrest. An Extreme Heat Warning has been issued for the desert areas also from Monday through Wednesday evening.

While still around a week away, there are indications in NBM cluster analysis that a trough will drop south into the Pacific northwest region. As of now, the trough is not expected to move into central California, however the influence of the trough may have an effect on the local temperatures, cooling the region down near season averages as the flow begins to prevail from the west. However, dry conditions will remain.

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

Extreme Heat Warning from 5 AM Monday to 11 PM PDT Wednesday for CAZ337>339. Heat Advisory from 5 AM Monday to 11 PM PDT Wednesday for CAZ304>316.