Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
594 FXUS66 KSTO 082037 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 137 PM PDT Mon Jul 8 2024 .SYNOPSIS... Hot and dry weather will continue this week with Moderate to Extreme HeatRisk persisting across much of the region. Elevated fire weather concerns will also continue. Cooler this weekend and into early next week. && Key Points - Long-duration, dangerous heat event persists this week. - Brief reprieve through Tuesday with slightly cooler temperatures, then warmup again Wednesday-Friday, followed by a cooldown over the weekend into next week - Excessive Heat Warning is in effect for the northern half of the Sacramento Valley and foothills through Friday, and from Wednesday-Friday for the southern Sac Valley/northern SJ Valley. - Heat Advisory is in effect for the Sierra, southern Cascades, and Burney Basin through Friday, and from Wednesday-Friday for the Delta area. .Discussion... Current GOES-West visible satellite imagery shows clear skies with abundant sunshine being observed across interior northern California on this Monday afternoon. Temperature observations are currently trending approximately 2 to 8 degrees cooler than this time yesterday afternoon, valid at 130 PM PDT. Slightly cooler temperatures are forecast today, and Tuesday as well as high pressure weakens slightly over the region. By Tuesday, HeatRisk will mainly be in the Moderate category for our area of responsibility, with just areas of Major and Extreme HeatRisk. Increased onshore flow through the Delta will help moderate temperatures Tuesday, especially in the vicinity of the Delta and adjacent Valley locations. By Wednesday, the ridge will strengthen and extend westward bringing another warmup to the region through the end of the week with widespread Major to Extreme HeatRisk. Highs are expected to peak on Thursday for much of interior NorCal. On Thursday, there is a 40 to 80 percent probability of hitting at least 110 degrees in the Valley (excluding Delta area). The Excessive Heat Warning for the northern/central Sacramento Valley and adjacent foothills remains in effect through Friday, as does the Heat Advisory in the mountains. Another Excessive Heat Warning will go into effect Wednesday through Friday, for the southern Sacramento and northern San Joaquin Valleys, with a Heat Advisory in the Delta over the same timeframe to address the increasing heat mid to late week. Plan ahead for the hot temperatures and be prepared to practice heat safety! Latest HeatRisk: wpc.ncep.noaa.gov/heatrisk/ Heat Safety Tips: weather.gov/safety/heat && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Ensemble guidance and cluster analysis indicate high pressure shifting to the east, over the Four Corners region, allowing for a cool down over the area with increased onshore flow, as well as mountain thunderstorm potentail along and east of the Sierra Crest, and even up into the Lassen area. The National Blend of Models (NBM) suggests a 10 to 15 percent probability for thunderstorm development over the aforementioned areas in the afternoon and early evening hours over the extended forecast period. Hot temperatures persist on Friday, with Moderate to Extreme HeatRisk across the forecast area, but HeatRisk decreases over the weekend down to Minor/Moderate by Sunday/Monday due to increased onshore flow and lowering heights over the area as the ridge sits over the Desert Southwest. The Excessive Heat Warnings and Heat Advisories run through 8 PM PDT Friday. && .AVIATION... VFR conditions over interior NorCal next 24 hrs with surface wind at or below 12 kts with afternoon gusts 15 to 20 kts (00z-04z Tuesday). In the Delta, southwesterly winds 15-25 kts with gusts 20 to 25 kts 23z Monday-18z Tuesday. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM PDT Friday for Central Sacramento Valley-Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley- Shasta Lake Area / Northern Shasta County-Southern Sacramento Valley. Heat Advisory until 8 PM PDT Friday for Burney Basin / Eastern Shasta County-Carquinez Strait and Delta-West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$