Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA
Issued by NWS San Joaquin Valley, CA
596 FXUS66 KHNX 220012 AFDHNX Area Forecast Discussion National Weather Service Hanford CA 412 PM PST Thu Nov 21 2024 .UPDATE...Updated air quality issues. && .KEY MESSAGES... 1. Temperatures will warm to around 5 to 10 degrees above climatological normals today and Friday. 2. A strong storm system is forecast to impact Central California Friday night through this weekend. Portions of the San Joaquin Valley and the Sierra Nevada foothills may see moderate to heavy rainfall rates at times with moderate to heavy snowfall rates in the Sierra Nevada. 3. A Winter Storm Warning has been issued for the Sierra Nevada above 6,500 feet valid from 4 PM Friday through 4 PM Tuesday. Accumulations 10 to 24 inches are possible with up to 4 feet at the highest elevations. Wind gusts could reach up to 50 miles per hour. The probability of receiving 18 inches of snow by 4 PM Saturday is 68% for Tuolumne Meadows and 74% for Tioga Pass. 4. The probability of receiving between one-half and one (0.5-1.0) inch of rain by 4 PM Saturday is 90% in Merced decreasing towards the south to 70% in Fresno, 50% in Visalia, and 15% in Bakersfield. && .DISCUSSION... A strong upper level low pressure system is currently located in the eastern Pacific, just off the coast of the Pacific Northwest region. Cyclonic flow around this system is driving moisture into northern California, Oregon, and Washington. Much of this moisture is not reaching central California as of yet due to a ridge of high pressure in place over the area, extending from the Desert Southwest. The subsiding air associated with the ridge is propagating dry conditions for central California with above normal temperatures expected today and tomorrow. Ensemble guidance from the National Blend of Models indicates a 60 to 90 percent chance for afternoon high temperatures to exceed 70 degrees each day in the San Joaquin Valley before falling to less than 10 percent through the end of next week. As the weekend approaches, the ridge will begin to weaken, allowing a stream of moisture to entrain over central California, beginning over the northern San Joaquin Valley and Sierra Nevada near Yosemite National Park, and tracking south through the weekend. The approaching trough will have two major waves associated with it as the center of the system remains mostly stationary off the coast of Washington state.The first wave will occur Friday evening through Monday morning. The following are probabilities for 72 hour rainfall totals to exceed one inch in the San Joaquin Valley ending at 4 AM PST Monday, November 25th. Bakersfield 15% Coalinga 35% Fresno 70% Hanford 40% Madera 80% Merced 90% Visalia 40% The system will also result in heavy snowfall in the Sierra Nevada, mainly above 6,500 feet, with the National Blend of Models expressing a 100 percent chance for snowfall greater than 12 inches for Tioga Pass, Tuolumne Meadows, and White Wolf Mountain. The Winter Storm Watch has been upgraded to a Winter Storm Warning for the Sierra Nevada above 6,500 feet from Yosemite National Park to the mountains north of Lake Isabella. This warning is valid for the entire event from 4 PM PST Friday, November 22nd until 4 PM PST Tuesday, November 26th. Accumulated snowfall between 10 and 24 inches is possible with high elevation snowfall up to 4 feet through the entire event. Southwest wind gusts could reach up to 50 miles per hour. The initial wave will also bring a chance for elevated winds in the Kern County Desert, including the Mojave Desert Slopes. There is a 50 to 80 percent chance for maximum wind gusts Saturday overnight into Sunday morning to exceed 30 miles per hour in this area. The second wave of this system is expected to move through central California Monday afternoon through Tuesday evening, continuing the stream of moisture through the region. Snow levels for the event early next week currently are forecast to be around 7,000 - 7,500 feet at the start of the event Monday, then falling to around 6,500 by Tuesday. Model guidance currently does not have this 2nd system early next week being quite as wet as the first; with rainfall amounts in the San Joaquin Valley currently projected to be around one quarter to one half of an inch. In the Sierra Nevada, another foot of snow is conceivable above 7,000 feet. This additional snow can lead to exacerbated snowload impacts due to it happening right on the heels of the weekend storm system. In terms of wind, right as the storm begins to encroach upon the region late Sunday/Early Monday, a reinforcement of a strong gradient across the mountains in Kern County may lead to strong winds through and below pass level. By Wednesday morning, some lingering moisture/cloud cover banked up against the northern facing slopes of the Tehachapi Mountains is forecast, leading to light rain and potential visibility issues through Highway 58 and Tejon Pass/I-5. The system is forecast to completely exit the area by late Wednesday. Ensemble guidance has been trending drier in the latter portion of the forecast (Wednesday and after). This is due to high pressure aloft that will shunt moisture from reaching Central California. However, the return of Tule Fog cannot be ruled out late next week due to high pressure and wet soil that enhance fog potential. && .AVIATION... There is a 2-5 percent probability for IFR conditions between 12Z and 15Z Friday morning. Otherwise, VFR conditions will prevail across the central California interier for the next 24 hours. && .AIR QUALITY ISSUES... On Friday November 22 2024, Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno and Kern Counties. Burning Discouraged in 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 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... Winter Storm Warning from 4 PM Friday to 4 PM PST Tuesday for CAZ323-326>331. && $$ public...SM/ab/BSO aviation....SM IDSS.......DAS weather.gov/hanford