Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
064 FXUS66 KSTO 172021 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 121 PM PDT Tue Sep 17 2024 .Synopsis... Dry today then cooler unsettled weather tonight through Wednesday. Lingering showers over the Sierra Nevada Thursday, otherwise drier and warmer conditions into early next week. && .Discussion... A quiet weather day expected with dry and cool conditions over Northern CA. Highs today and Wednesday will be in the mid 70s to low 80s in the Valley with upper 60s to mid 70s over the foothills as cooler weather continues ahead of our next weather system. Our next weather system moves in from the Pacific NW tonight through Thursday AM. Compared to Sunday`s system, this system is tracking further south and is warmer. This translates to as a weaker thunderstorm signal for our area and lesser chances for snow along the peak of the Sierra. Current probability is 15-30% of thunderstorm development over the Sierra and adjacent foothills with highest chances along the ridge of the Sierra Wednesday afternoon and evening (Wed 21z - Thu 03z. Forecast show around 0.10-0.50 over the Sierra and foothills, up to just under an inch along the Sierra crest. Probabilities of exceeding 0.25" for the aforementioned area is 55-80% over the Sierra with 40-60% over the foothills. The lower portions of the Valley (below 1000 feet) have 10-30% chance, which is more so indicating the slight chance of showers moving through the Valley than any organized stratiform precipitation. This weather pattern will bring another chance of debris flow issues over the Park Fire burn scar, albeit less synoptic support compared to last weekend. One hi-res model simulations shows isolated thunderstorms tracking over the burn scar early Wednesday afternoon from east to west until Wednesday evening around 8pm local. After Thursday morning, heights are expected to rise behind the weather system, returning temperatures to near normal by weekend`s end. Thursday and Friday will see afternoon highs warm to the mid 90s to low 90s in the Valley with upper 60s to mid 80s across the mountains to foothills areas. With the warming temperatures, afternoon humidities lower back to 20-30% over the Northern Sacramento Valley. && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... Dry weather expected through the extended forecast period as high pressure extends inland over NorCal. Warming trend forecast over the weekend into early next week with 90s returning in the Central Valley and 60s to 80s for the mountains and foothills. && .AVIATION... Mainly VFR conditions and surface winds below 12 knots over interior Northern California. Isolated MVFR/IFR conditions may happen due to rain showers. Southwestrly winds up to 20 knots are possible in the Delta region. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$