Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
290 FXUS66 KSTO 110949 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 249 AM PDT Tue Jun 11 2024 .SYNOPSIS... Hot temperatures through Wednesday with Moderate to Major HeatRisk. Temperatures will trend cooler late in the week and over the weekend. Isolated shower/thunderstorms over the Sierra Crest south of Highway 50 this afternoon. Elevated fire weather conditions this weekend. && .DISCUSSION... Key Points - An Excessive Heat Warning for areas north of I-80 remains in effect through Wednesday evening with Major HeatRisk and widespread triple digit highs. - A Heat Advisory for areas south of I-80 remains in effect through Wednesday with widespread Moderate HeatRisk and areas of Major HeatRisk. - Local waterways are still running cold and fast from snowmelt Short-Term Discussion (Today THROUGH Friday)... Current GOES-West satellite imagery shows generally clear skies across interior northern California early on this Tuesday morning. Current temperatures are trending approximately 3 to 10 degrees warmer than this time yesterday morning, valid at 230 AM PDT. The forecast largely remains on track for hot temperatures to impact the area today, with forecast highs in the triple digits for much of the lower elevations. Overnight temperatures will also be warm, in the 60s to mid 70s for the Valley and foothills. Moderate to Major HeatRisk has warranted an Excessive Heat Warning (mainly north of I-80), and a Heat Advisory (mainly south of I-80) that both remain in effect through Wednesday evening. The extent of the Delta Breeze influence and increased onshore flow on Wednesday may allow for part or all of the advisory (not the warning) to be dropped earlier tomorrow. There is a 10-20% probability for a shower/thunderstorm over the Sierra Crest south of Highway 50 this afternoon and evening. Elsewhere, dry conditions prevail over the next several days. For later this week, temperatures are expected to trend cooler as a low pressure area approaches from the Gulf of Alaska. Increased onshore flow and cooler temperatures are expected from the influence of the low. In terms of HeatRisk, over the Thursday and Friday timeframe, mainly Minor HeatRisk prevails across our area of responsibility, with just some localized Moderate HeatRisk mainly in the northern/central Sacramento Valley. Forecast highs in the Valley are projected to be in the 80s to 90s later this week, which will be cooler than today-Wednesday, but still trending above normal for mid June climatology. Additionally, area waterways continue to run fast and cold from snowmelt, creating dangerous conditions for those seeking relief in rivers and lakes. Be sure to practice heat and cold water safety this week! 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 (Saturday THROUGH Tuesday)... Long wave trough sets up along the West Coast over the weekend and persists into early next week as several short wave troughs move through 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 resulting in some gusty northerly wind in the Central Valley and elevated fire weather conditions. && .AVIATION... Generally VFR conditions over interior NorCal next 24 hrs except possible isolated MVFR in tstm over higher terrain of Alpine and Tuolumne counties btwn 20z-03z. Sfc wind mainly below 12 kts except vcnty of Delta aft 00z Wed SWly sfc wind up to 20 kts possible. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning from 11 AM this morning to 8 PM PDT Wednesday 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. Heat Advisory from 11 AM this morning to 8 PM PDT Wednesday for Carquinez Strait and Delta-Motherlode-Northern San Joaquin Valley-Southern Sacramento Valley. && $$