National Weather Service - Discussion
Area Forecast Discussion
National Weather Service - San Joaquin Valley / Hanford, CA
Issued: Friday, December 8 2023 - 4:09 AM PST
SYNOPSIS... A cooling trend will continue over the forecast region into the weekend as northwesterly flow sets up aloft. Stronger winds are projected to continue in the Mojave Desert Slopes this morning with reasonable confidence of recurrence in the southern Tehachapi mountains on Saturday with the development of Santa Ana winds. Freezing temperatures are possible across the rural areas of the San Joaquin Valley late Friday night and each subsequent night through next Wednesday.
DISCUSSION... An upper level longwave trough will exit eastward from the region later today, setting up a cooling trend into the weekend. Cyclonic flow around the trough sets up northwesterly winds aloft on the western aspect of the retreating system, allowing cooler air to enter the Central Valley region from the north Pacific. Maximum temperatures as a result are projected to return to climatological normals in the upper 50s for the San Joaquin Valley and the Kern County Desert. The entrainment of cooler air will also cause morning lows to approach or fall below freezing in the rural areas of the San Joaquin Valley. This has led to the upgrade of a Freeze Watch to a Freeze Warning in effect from late Friday night until Wednesday morning. The following are chances from probabilistic guidance for sub-freezing morning temperatures for select areas of the San Joaquin Valley.
Madera 89% Hanford 74% Merced 74% Fresno 4% Bakersfield 0%
The northwesterly flow through the lower levels of the atmosphere are expected to continue the stronger winds in the Mojave Desert Slopes through this morning. Calmer winds are expected this afternoon into the overnight. However, there is medium confidence (60 to 70%) for winds to pick up again in the southern Tehachapi mountains Saturday as a surface high pressure system brings an increase in the Santa Ana winds. Otherwise, clear and stable conditions will be present through the weekend and entering next week, resulting from an upper level ridge that will progress over the region. This ridge will bring a slight increase in temperatures, with highs Sunday and Monday projected to be in the low 60s, around 5 degrees above normal.
Zonal flow will set up aloft over the Central Valley early next week which is expected to keep conditions relatively consistent from the weekend. Cluster analysis is trending towards a stronger upper level ridge developing midweek, bringing additional warming to the forecast area. Probabilistic guidance suggests a 30-60% chance for maximum afternoon temperatures to exceed 65 degrees in the San Joaquin Valley Wednesday and Thursday.
AVIATION... MVFR conditions in areas of mist/haze with local IFR/LIFR in fog possible until 18Z Friday. Otherwise, VFR conditions will prevail across Central California over the next 24 hours.
AIR QUALITY ISSUES... ISSUED: 12/07/2023 15:00 EXPIRES: 12/08/2023 23:59 On Friday December 8, 2023, 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.
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 7 AM PST this morning for CAZ338.
Freeze Warning from 2 AM Saturday to 8 AM PST Wednesday for CAZ301>303-305-306-309>312-315.