textproduct: San Joaquin Valley

KEY MESSAGES

1. Lake Wind Advisory continues for West Side Coastal Mountains north of 198 and San Luis Reservoir through 11 PM PDT Saturday, July 4th, beware of unsettled waters.

2. Dry and breezy conditions create elevated fire risk into next week, especially in the Mojave Desert.

3. Near-normal temperatures expected across the area today, then a warming trend over the holiday weekend.

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

DISCUSSION

A slightly warmer day is on tap for today with highs in the mid 90s at the warmest valley locations and mid to upper 90s in the Kern County desert. An upper-level trough prevails over much of the Western U.S., although with a zonal flow over our forecast area. This pattern will give way to high pressure ridging over the next several days, but with shortwave troughs embedded in the flow aloft at times. This will lead to a gradual warmup in temperatures, but with diurnal winds remaining breezy towards the Coastal Ranges and West Side Hills. Will keep the Lake Wind Advisory for San Luis Reservoir and nearby areas until 11 PM Saturday with gusts to 30 mph each afternoon and evening. The chances for 25 mph gusts remain at 50-60 percent for this particular area during this afternoon into the evening, according to latest high resolution ensemble guidance. Breezy conditions will also occur along the Mojave Desert slopes and lee side of the southern Sierra Nevada. In addition, a 10-15 percent chance for thunderstorms exists again this afternoon and early evening along the Sierra Nevada crest, mainly north of Fresno County. Otherwise, a dry pattern prevails with low daytime humidity in many locations, including near 10 percent minimum humidity in the Mojave Desert and teens and lower 20s for the San Joaquin Valley and southern Sierra Nevada in Tulare County southward. The low humidity combined with afternoon breezes will contribute to an elevated fire weather risk each day.

Heat becomes more of a concern as we progress. Probabilities for high temperatures above 100 degrees rise to 10-20 percent in the San Joaquin Valley by Independence Day and 50-60 percent in the Mojave Desert in eastern Kern County. The chances lower a bit on Sunday and Monday, but rise back to 15-25 percent by Tuesday for the Central Valley and 70-80 percent for the Mojave Desert. The upward trend in probabilities will last through the end of next week and likely beyond. We see little or no precipitation for the period, other than the slight chance for afternoon high Sierra thunderstorms each afternoon.

Latest CPC outlooks favor above average temperatures for both the 6-10 day and 8-14 day periods. The CPC also continues to mention a Moderate Risk of hazardous temperatures for July 12-15th over much of California with a Slight Risk on the 10th until the 16th. Basically, this means widespread triple digit heat for a prolonged period and strong high pressure in control. We will continue to monitor as we get closer, and if confidence increases further, we are looking at the hottest period of the year so far.

AVIATION

VFR conditions expected across the area for the next 24 hours. Slight (10-15%) chance of thunderstorms along the Sierra Nevada crest Devil's Postpile and north 21Z Fri-03Z Sat.

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

Lake Wind Advisory until 11 PM PDT Saturday for CAZ300.