Area Forecast Discussion

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National Weather Service - San Joaquin Valley / Hanford, CA
Issued: Tuesday, April 1 2025 - 4:07 AM PDT

UPDATE... Updated Aviation Section.

KEY MESSAGES...

* Precipitation will continue to move through the forecast area through midweek, with only eastern Kern County not seeing 100% probability of measurable rainfall. Eastern Kern County probabilities range from 60% over the mountains to 25% along the county line.

* Moderate to heavy snow expected in the Sierra through midweek, with 1-3 feet of snow in Mariposa, Madera, and Fresno (north of the Kings River) Counties and up to 10 inches in Fresno, south of the Kings River, and Tulare Counties.

* Winter Storm Warning in effect for Sierra north of the Kings River and a Winter Weather Advisory south of the river.

* Snow levels will drop on Tuesday from 6kft to 3500 ft, though the majority of the snowfall will occur before the snow levels drop. Light snow accumulations down to 3500 ft will be possible.

* Strong winds expected Monday through Wednesday across the Sierra Crest, the lee slopes of Kern County Mountains and the Kern Desert. 80% probability of greater than 70 mph max gust on Tuesday for Mojave.

* High Wind Warning in effect for the lee slopes of the Tehachapi Mountains and a Wind Advisory for the Kern Desert.

DISCUSSION... We have a trough sliding into California slowly today and tomorrow. This trough is bringing showers to the valley and snow to the Sierra Nevada. A Winter Storm Warning is in effect for most of the Sierra Nevada with 1 to 3 feet of snow expected and 6 to 12 inches of snow expected in the Southern Sierra south of the Kings River. In the Valley, we are looking at a 45 to 70 percent chance of a quarter inch or more of rain total with this system with the foothills having a 30 to 80 percent chance of an inch or more of rain.

This trough also is bringing strong winds to the Mojave Slopes and Desert due to the positioning which favors downslope winds and a very tight gradient which increases wind speeds. A High Wind Warning is in effect for the lee slopes of the Tehachapi Mountains and a Wind Advisory is in effect for the Kern Desert through 5 AM Wednesday. There is a 80 percent chance of max wind gusts of at least 70 mph in Mojave on Tuesday from this system.

The trough will slowly slide south Wednesday and Thursday before a ridge slides in Friday into the weekend. This ridge will bring dry conditions and warming temperatures. Sunday has a 35 to 70 percent chance of high temperatures reaching the 80s again. The long term outlooks have a 40 to 60 percent chance of above average temperatures for the San Joaquin Valley and goes from a 33 to 40 percent chance of below average precipitation to equal chances of above and below average precipitation.

AVIATION... 12Z Update: Across the San Joaquin Valley, mainly VFR conditions. Will see -SHRA with a 15%-20% chance of isolated TS after 18Z Tuesday and -RA can be expected until 06Z Wednesday.

Over the Sierra Nevada and Kern County mountains, widespread IFR with areas of mountain obscuring LIFR conditions in clouds and precipitation for the next 24 hours.

For the Kern County Desert, strong winds will continue through the forecast period. Surface wind gusts greater than 50 kts are expected in the Mojave Slopes from 00Z through 12Z Tuesday and after 18Z Tuesday.

Otherwise, VFR for the next 24 hours.

AIR QUALITY ISSUES... None.

CERTAINTY...

The level of certainty for days 1 and 2 is medium. 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... Wind Advisory until 5 AM PDT Wednesday for CAZ337-339. High Wind Warning until 5 AM PDT Wednesday for CAZ338. Winter Storm Warning until 11 PM PDT Tuesday for CAZ323-326- 327. Winter Weather Advisory until 11 PM PDT Tuesday for CAZ328>331.