textproduct: San Joaquin Valley

UPDATE

Updated for 12Z Aviation.

KEY MESSAGES

1. Strong system moves in through Thursday bringing moderate rain and heavy snow to the region.

2. Winter Storm Warning in effect through 10 PM Thursday for the Sierra Nevada and through 10 PM Wednesday for the Kern County mountains.

3. Winter Storm Warning in effect through 9 AM Thursday for the I-5/Grapevine area.

4. Strong wind gusts expected along area mountain ranges, along with the Mojave Desert and portions of the southern San Joaquin Valley. Wind Advisory in effect through 4 pm Wednesday for the West Side Hills and Mojave Slopes.

5. General risk of thunderstorms for much of the region this afternoon and evening.

DISCUSSION

Numerous showers will continue to affect the area tonight into Tuesday. Gusty mainly S winds will also impact portions of the area, strongest over the westside mountains and into the mtns and deserts. Advisory level gusts of up to 50 mph are expected and Wind Advisories are in effect for these areas.

With increasingly cold air aloft (down to -28 deg C at H5 this evening), cyclonic flow and the area near a 100 kt jet exit region, there is a slight chance of thunderstorms lingering this evening mainly over northern portions of the forecast area. Some thunderstorms could have heavy rain, small hail and strong, gusty winds.

As the main energy with this first storm system moves E tonight, it looks like rainfall will taper off some over the San Joaquin Valley but with moist WSW flow at mid levels levels persisting, additional significant precipitation is expected in the Sierra, with snow levels continuing to lower down to near 3000 feet north to 4000 feet south by early Tuesday morning. Snow levels will also lower to near 4000 feet in the Tehachapi Mtns by early Tuesday morning.

A second storm system and cold upper level trof will affect the area generally from Tue afternoon through Wed. Additional significant rain and mountain snow are expected, along with a slight chance of thunderstorms Tue afternoon and evening for central and northern parts of the forecast area.

The most significant concern with the storms this week is the snow and its impacts. This is especially true Tue into Wed as a stronger, colder second trough slides through the area, lowering snow levels to 2000 to 2500 feet by 7 AM Wed. The best case (low end) snow amounts shows a 90 percent chance of 2 to 3 feet of snow above 5000 feet and 3 to 4 feet above 7000 feet. On the other extreme, the worst case shows 5 to 6 feet above 5500 feet and 6 to 8 feet above 7000 feet. The lowering snow elevations also brings the potential for snow on the passes as there is a 21 percent chance of 4 inches of snow on Tejon Pass and a 5 to 20 percent chance of 4 inches of snow on Tehachapi Pass. There also is a 5 to 10 percent chance of a trace even in the Valley.

The second storm system will bring a 45 to 60 percent chance of another half an inch of rain ending 4 PM Wed for the Valley. As the trough lifts on Thu and Fri, a shortwave trough slides across northern California bringing another chance of showers, but lighter. Temperatures will remain below average heading into the weekend. In the long term, the CPC shows a change. The temperature outlooks go from a 33 to 40 percent chance of below average temperatures in the 6-10 day outlook to near normal in the 8- 14 day outlook. Both the 6-10 and 8-14 day outlooks continue to favor above average precipitation at 40 to 50 percent for the Valley.

AVIATION

CIGs continue around FL050 with occasional periods with CIGs around FL020. Precipitation will continue across all TAF sites through the forecast period, with heavier precip rates causing periodic MVFR conditions through 12z Wednesday. IVR to MVFR conditions in the mountains due to precipitation. 10 to 20% chance for thunderstorms until 12Z Wednesday. Winds at the TAF sites primarily near or below 12 kts until around 17z Tuesday when gusts will increase to 25-30 kts.

AIR QUALITY ISSUES

On Tuesday February 17 2026, Fireplace/Wood Stove Burning Status is: Burning Discouraged in Fresno, Kern, Kings, Madera, Merced, and Tulare Counties, and Kern (Greater Frazier Park Area) and Sequoia National Park and Forest.

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

Wind Advisory until 4 PM PST Wednesday for CAZ300-308-313- 337>339. Winter Storm Warning until 10 PM PST Thursday for CAZ318-320- 322>331. Winter Storm Warning until 10 PM PST Wednesday for CAZ333-334- 336. Winter Storm Warning until 9 AM PST Thursday for CAZ335.