Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
736 FXUS66 KSTO 121030 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 330 AM PDT Wed Jun 12 2024 .SYNOPSIS... Hot temperatures through this evening with Moderate to locally Major HeatRisk north of I-80. Temperatures will trend cooler late-week and over the weekend. Isolated shower/thunderstorms over the Sierra Crest south of Highway 50 Thursday afternoon. Elevated fire weather conditions this weekend into early next week. && .DISCUSSION... Key Points - Hot temperatures continue through this evening, mainly north of I-80 where there is widespread Moderate HeatRisk with local Major HeatRisk today - Cooler Thursday, with closer to normal temperatures through the weekend - Slight chance of shower/thunderstorm over the Sierra Crest south of Highway 50 Thursday afternoon - Elevated Fire Weather Conditions later this weekend into early next week from gusty northerly wind and low RH - Local waterways are still running cold and fast from snowmelt Short-Term Discussion (Today THROUGH Saturday)... Current GOES-West satellite imagery shows mostly clear skies across interior northern California on this early Wednesday morning. Temperature observations are currently trending approximately 2 to 10 degrees warmer than this time 24 hours ago, valid at 330 AM PDT. Hot temperatures are expected to continue today, mainly in the lower elevations north of Interstate 80 where triple digit temperatures are still likely again for the daytime high, and Moderate HeatRisk and local Major HeatRisk are forecast. For areas south of Interstate 80, mainly Minor to Moderate HeatRisk is expected for today as temperatures will be trending cooler than Tuesday with the assistance of increase onshore flow. As a result, the Heat Advisory has been cancelled. The Excessive Heat Warning north of I-80 remains in effect through this evening. Cooler temperatures return to the area Thursday and continue into the weekend with increased onshore flow late-week. High temperatures during this time are expected to be in the 80s to 90s in the Valley, 80s to around 90 in the foothills, and 60s to 80s in the mountains. These temperatures will be trending closer to normal for this time of year, with primarily Minor HeatRisk Thursday through Saturday. There is also about a 10-20% probability of shower/thunderstorm over the Sierra Crest south of Highway 50 on Thursday afternoon. Beginning Saturday, increased northerly flow and lowering relative humidity are expected over the Valley, with increasing concerns later in the weekend. On Saturday, northerly wind gusts up to 15 to 25 mph are forecast in the Valley, strongest in the northern Sacramento Valley, and northern San Joaquin Valley. Minimum relative humidity values are currently projected to be in the 10-20% range in the Valley, with poor recoveries Saturday night, lowest in the northern and central Sacramento Valley and adjacent terrain. Elevated fire weather conditions continue into the extended forecast period. To view the latest HeatRisk, please visit www.wpc.ncep.noaa.gov/heatrisk/ To view current water temperatures, please visit www.cnrfc.noaa.gov && .EXTENDED DISCUSSION (Sunday THROUGH Wednesday)... Long wave trough sets up along the West Coast over the weekend and persists through midweek as several short wave troughs move across the PacNW. Synoptic cooling with increased onshore flow expected. High temperatures in the Central Valley projected in the upper 80s to lower 90s with upper 60s to 80s for the mountains and foothills. Low level north-south pressure gradient strengthens over interior NorCal this weekend. Upper level support then increases early next week. This will result in gusty north to east wind in the Central Valley and adjacent foothills Saturday into Tuesday with elevated fire weather conditions. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. Sfc wind mainly below 12 kts except in S Sac aft 21z areas Sly sfc wind up to 20 kts and N San Joaquin Vly aft 21z, areas NWly sfc wind up to 15 kts. Vcnty Delta SWly sfc wind 15-30 kts. Lcl gusts up to 40 kts possible aft 18z. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM PDT this evening for Central Sacramento Valley-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley- Northern Sacramento Valley-Shasta Lake Area / Northern Shasta County. && $$