textproduct: San Joaquin Valley

KEY MESSAGES

1. Lingering moisture will continue producing showers from time to time through this afternoon. Showers may produce excessive runoff with flooding.

2. High confidence of heavy snow above 7000 feet, with snow load impacts on roofs in the high Sierra continues. Snow will diminish by this evening. Travel will be difficult with winds gusting up to around 25 mph.

3. Thunderstorms are possible through this afternoon across the Joaquin Valley.

DISCUSSION

A mid-level jet will eject through the main trough today as the trough axis finally moves inland. This process will allow for a weakening trend in the upper level support, while orographic lift diminishes with the loss of mid-level flow. The inland transition of the upper level trough will steepen low to mid- level lapse rates and allow for another shot of shower activity with isolated thunder this afternoon. With heavier rainfall rates possible with this convective activity today, a Flood Watch remains in effect through this afternoon. The Winter Storm Warning also continues through this evening until the main trough swings through. Up to around a foot of additional accumulation in the High Sierras remains likely based on the recent 12Z HREF run.

The upper level pattern this weekend into next week will likely see broad ridging develop over the Pacific Northwest with positive height anomalies drifting into California. The subsidence pattern will bring near to just below normal temperatures with light and variable winds. Later in the week, an upper low over the tropical Pacific may lift north toward southern CA as another trough approaches from the north. Recent NBM runs over the previous 24-48 hours have seen precipitation chances for the second half of the work week increase, though details remain to be worked out.

AVIATION

Showers will gradually decrease in coverage through 00Z-06Z, with lingering isolated showers late. Some isolated TS may be possible, confidence is less than 20 percent thus was not mentioned in the TAFs. Brief MVFR cigs and visibility possible with any of these showers.

With a moist boundary layer in place and winds becoming light and variable after 06Z, visibilities may fall to MVFR levels with the best potential from VIS to MCE.

Winds generally light and under 10 kts, with an occasional gust to 18 kts through the early evening especially near showers. Surface winds remain light tomorrow and turn to the northwest after 16Z.

AIR QUALITY ISSUES

On Friday December 26, 2025, 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

Flood Watch until 4 PM PST this afternoon for CAZ300>339. Winter Storm Warning until 10 PM PST this evening for CAZ323- 326>331.