Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
047 FXUS66 KSTO 052129 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 229 PM PDT Sat Oct 5 2024 .Synopsis... Well above normal temperatures persist through the weekend, with Moderate to Major HeatRisk in the Valley, Delta and foothills. Slight chance of high elevation mountain showers Sunday and Monday afternoon over the Sierra Crest. Gradual cooling trend next week with shower chances mainly north of I-80 and over higher terrain. .Discussion... Current GOES-West visible satellite imagery shows clear skies with abundant sunshine being observed across interior Northern California on this Saturday afternoon. Current temperature observations are trending approximately 2-5 degrees higher than this time 24 hours ago, in the 90s in the Valley, Delta, and lower foothills, and 70s-low 90s in the upper foothills and mountains, valid at 230 PM PDT. Upper level ridging is allowing for unseasonably hot temperatures and dry conditions to prevail through the weekend. Widespread Moderate to Major HeatRisk is expected through Sunday in the Valley, Delta and foothills. Forecast highs remain in the 90s to low 100s, with warm overnight lows in the 60s to mid 70s. The Heat Advisory remains in effect through 11 PM PDT Sunday evening for those aforementioned locations. Temperatures cool slightly on Monday but are still unseasonably hot, with Moderate HeatRisk across the Valley and foothills. A few isolated mountain showers will be possible over the Sierra Crest on Sunday and Monday afternoons as a subtle trough approaches the region. By Tuesday, temperatures look to be on a gradual downward trend with highs in the 90s in the Valley, 80s in the foothills and 70s to 80s in the mountains. HeatRisk lowers to the Minor category with just some localized Moderate HeatRisk. Low daytime relative humidity continues, in the teens and 20s through Tuesday, with moderate to poor overnight recoveries. && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday)... Ensemble guidance and cluster analysis indicate upper level troughing developing over the Eastern Pacific and approaching from the west mid to late next week, bringing a cooling trend through the end of the week with increased onshore flow. HeatRisk is expected to decrease and remain in the Minor category over the extended forecast period. The troughiness will also bring a chance for showers toward the end of the week. There is still some uncertainty in exact timing and details, however the National Blend of Models (NBM) currently advertises a 10-25% probability of a tenth of an inch of precipitation or greater on Friday, mainly north of Interstate 80 and over higher terrain. On Saturday, upper level ridging looks to build back in behind the trough resulting in slightly warmer temperatures and increased northerly flow. && .AVIATION... VFR conditions are expected over interior northern California for the next 24 hours. Surface winds are generally expected to be below 12 knots except for locally northeast or northwest surface wind up to 15 knots with gusts up to 20 knots in the Delta, foothills and mountains after 10Z Sunday. && .STO WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 11 PM PDT Sunday for Carquinez Strait and Delta-Motherlode-Northern San Joaquin Valley-Southern Sacramento Valley. && $$