Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
158 FXUS66 KSTO 242132 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 232 PM PDT Tue Sep 24 2024 .Synopsis... Hot weather with Moderate HeatRisk is expected today, before temperatures cool down tomorrow and Thursday. Warmer and drier conditions return on Friday and continue into early next week. && .Discussion... GOES-West visible satellite imagery shows clear and sunny skies across interior Northern California this afternoon. Temperatures in the Valley (as of 1:11 pm) are well into the 90s with slightly cooler highs in the mid 80s to low 90s around the Delta and light southwesterly winds. We`re still on track to see high temperatures in the upper 90s across the Valley and the potential for triple digit temperatures this afternoon. These above-normal high temperatures combined with elevated Valley/foothills overnight lows in the 60s to low 70s, widespread Moderate HeatRisk is expected across the Delta, Valley, and foothills through this evening. So be sure to stay hydrated and practice heat safety! HeatRisk drops down to Minor tomorrow and Thursday with near- normal temperatures, as closed low located offshore begins to phase with descending longwave from the Pacific Northwest bringing in cooler air. As this feature deepens into Wednesday, westerly winds will increase through the Delta tonight with gusty southwesterly winds (15 to 25 mph) developing through the Valley by tomorrow afternoon. NBM probabilities indicate a 50 to 70% chance of gusts greater than 30 mph through the Delta, and a 20 to 40% chance of gusts greater than 25 mph throughout the Valley. Humidity values will also increase Wednesday as cooler, more moist air intrudes into the Valley. By Thursday, temperatures increase slightly as broad upper level ridging begins to set up. Winds return to a diurnal pattern as more zonal upper level flow overtakes the area. A weak closed low off the Baja California coast and the aforementioned ridging will lead to somewhat stagnant heights and another slight warming trend Friday and into the weekend. A brief period of northerly winds and daytime humidity values in the teens and low 20s, may lead to another period of elevated fire weather conditions on Friday. && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... The extended forecast period looks to be fraught with variability in terms of the overall pattern. Some ensemble and cluster solutions show elevated 500 mb heights throughout the extended period, while others show brief interludes of troughing over interior NorCal. Currently, Saturday does appear to be the warmest day between this weekend and Tuesday of next week; NBM has probabilities of temperatures at or over 95 degrees at 40 to 75%. Sunday and beyond will depend on how much influence is exerted by low pressure to the southwest and northwest on the overall upper level pattern. In general though, we can expect temperatures to be about 5 to 10 degrees above normal for the time of year. Some areas of Moderate HeatRisk can also be expected in portions of the Valley. In general, we can also not discount some level of Elevated Fire Weather Concerns early next week either. Between very dry daytime conditions, poor overnight recoveries in humidity, and potential for breezy winds depending on the exact placement of the upper level pattern early next week, it will be important to keep an eye on things as Fire Weather Concerns have the potential to change over the next few days. && .AVIATION... VFR conditions persist across interior NorCal next 24 hours. Surface winds generally less than 12 kts expected. Some gusts up to 30 kts possible across the Delta vicinity from 05Z to 16Z Wednesday. Gusts up to 20 kts are possible for few hours across the Valley after 18Z Wednesday. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$