Marine Weather and Tide Forecast for Mammoth Lakes, CA

KEY MESSAGES
1. Fog and low clouds will continue each night and morning across the San Joaquin Valley into this week. Dense fog will also develop at times in the lower Sierra foothills, coastal ranges, and the Grapevine.

2. A gradual warming trend will occur in the mountains and desert until next week, as the high pressure pattern continues over the region.

DISCUSSION
Conditions today remain in a "rinse and repeat" pattern, with low clouds spanning across the San Joaquin Valley and areas of fog and reduced visibilities in the foothill areas where these clouds encounter the local terrain. This pattern comes as the result of a strong temperature inversion extending to 6000 feet above ground level which is trapping saturated air between 1000 and 2000 feet. In fact, the warmer temperatures are anomalously warm for this time of year, running around five degrees celsius above average. Without warmer temperatures and/or drier conditions at the surface, or increased winds to mix out the low clouds, our valley stratus will look to continue at least through midweek.

As the mid to late week period approaches, the high pressure ridge over the eastern Pacific driving our stable conditions is projected to slide eastward, based on current ensemble forecasts. This pattern change is expected to cause increasingly anomalous temperatures, especially for the Sierra Nevada and surrounding foothills, and in the Kern County Desert.
Probabilistic guidance shows areas including Lake Isabella, Oakhurst, and Yosemite Valley have more than a 90 percent probability for maximum temperatures to exceed 70 degrees this coming Friday, when these locations average 50 to 60 degrees. It will remain to be seen what this system does for the San Joaquin Valley. Warmer temperatures caused by the ridge will bring afternoon highs nearer to season averages, which could lead to clearing conditions during the day, however the subsidence aloft caused by the high pressure would keep moisture trapped in the lower levels. These warm and dry conditions are likely to remain into the extended period, as the Climate Prediction Center expresses a 70 to 80 percent chance for above average temperatures and 33 to 50 percent chance for below average precipitation.




AVIATION
IFR to MVFR ceilings and visibilities are expected to prevail for much of the San Joaquin Valley. These conditions will continue through 18Z Monday. LIFR conditions will also persist in the coastal ranges, Sierra foothills, and the Kern County mountains due to the low stratus deck. Otherwise, VFR conditions will prevail in the Sierra Nevada and in the Kern County Mountains and Desert over the next 24 hours.

AIR QUALITY ISSUES
ISSUED: 12/07/2025 14:17 EXPIRES: 12/08/2025 23:59

On Monday December 8 2025, Unhealthy for Sensitive Groups in Fresno, Kern, Madera, and Tulare Counties. Fireplace/Wood Stove Burning Status is: No Burning For All in Fresno, Kern, and Madera Counties. No Burning Unless Registered in Kings, Merced, and Tulare Counties. Burning Discouraged in Kern (Greater Frazier Park Area) and Sequoia National Park and Forest.

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
Dense Fog Advisory until 11 AM PST Monday for CAZ300-304-308- 313-316>322-334>336.