Area Forecast Discussion

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National Weather Service - San Joaquin Valley / Hanford, CA
Issued: Friday, December 20 2024 - 9:10 PM PST

UPDATE...Updated Aviation.

KEY MESSAGES...

1. Temperatures will be 6 to 12 degrees above normal through Tuesday.

2. There is a 15 to 35 probability of any rain accumulating this weekend in the San Joaquin Valley from Fresno northward.

3. There is a 50 to 90 percent probability of a tenth of an inch of rain in the San Joaquin Valley on Tuesday.

4. There is a 30 to 50 percent probability of eight inches or more of snow above 7000 feet in the Sierra Nevada on Tuesday into early Wednesday. There is 20 to 40 percent probability on Thursday over the same area.

5. There is a 60 percent probability of wind gusts exceeding 45 mph along the Mojave Slopes on Tuesday. The rest of the Kern County Desert has a 10 to 35 percent probability of exceeding 45 mph during the same time frame.

DISCUSSION... Widespread dense fog formed in the San Joaquin Valley overnight and persisted in much of the valley this morning. Visibility imagery is indicating the fog is finally dissipating with noted improvement in visibility noted on the east aide and south end of the valley. SREF is indicating that the fog and stratus should clear out across the valley this afternoon. Elsewhere across our area, satellite imagery is showing some thin high clouds streaming across our area being pulled up from the southwest ahead of an upper low pressure system approaching the PAC NW coast.

The aforementioned upper low is progged to push inland across the PAC NW on Saturday afternoon and evening and bring a slight chance of light precipitation as far south as the northern portions or Merced and Mariposa Counties. In the meantime, some areas of fog might reform in the San Joaquin Valley this evening, but the low to our north might provide for enough mixing to inhibit widespread fog formation like we had in our area this morning. Will therefore hold off on issuing any highlights for fog at this time.

SREF is showing chances of some warm air advection precipitation associated with a weak system north of our area from Fresno County northward on Sunday with QPF progs indicating a tenth to a quarter inch of liquid precipitation for the Yosemite area and less than a tenth of an inch of precipitation elsewhere with areas south of Fresno County remaining dry. NBM is indicating a 15 to 35 probability of any rain accumulating this weekend in the San Joaquin Valley from Fresno northward.

This system will also likely provide for enough clouds to inhibit fog from forming in the valley on Satruday night and Sunday morning. Shortwave ridging is progged for Monday with dry conditions and above normal temperatures prevailing across our area.

Ensemble members are still in good agreement with a strong low pressure system moving through northern California on Tuesday which will bring a period of precipitation to our area between Tuesday morning and Tuesday evening. NBM is indicating a 50 to 90 percent probability of a tenth of an inch of rain in the San Joaquin Valley and a 30 to 50 percent probability of eight inches or more of snow above 7000 feet in the Sierra Nevada as well as a 60 percent probability of wind gusts exceeding 45 mph along the Mojave Slopes. This system is progged to move to the east into the Great Basin by Christmas Day with shortwave ridging prevailing over our area for a dry conditions and more seasonable temperatures. NBM is indicating another system will bring mostly cloudy skies and some light precipitation to our area on Thursday and Thursday night.

AVIATION...06Z Update:

San Joaquin Valley and West Side Hills: Mainly IFR until 18Z Sat, with areas of LIFR in fog. After 18Z Sat, mainly MVFR in mist and haze with areas of IFR in mist and haze.

In the High Sierra/Foothills and Tehachapi Mountains, VFR conditions are expected to prevail for the 24 hour period.

Kern County Desert remains VFR for the 24 hour period.

AIR QUALITY ISSUES... On Saturday December 21 2024, Unhealthy for Sensitive Groups in Kern County. Fireplace/Wood Stove Burning Status is: No Burning For All in Kern County. No Burning Unless Registered in Fresno, Madera, and Tulare Counties. Burning Discouraged in Kings and Merced Counties, and 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... None.