Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
246 FXUS66 KSTO 292006 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 106 PM PDT Sat Jun 29 2024 .SYNOPSIS... Critical fire weather conditions for portions of the Valley Tuesday and Wednesday. Dangerous heat with major and extreme heat risk values Tuesday through late next week. && Key Points - Long-duration, major heat event expected this week impacting holiday outdoor events. - Excessive Watch has been upgraded to Excessive Heat Warning for the Valley, Delta and foothills from Tuesday morning through Saturday evening. - The Fire Weather Watch has been upgraded to a Red Flag Warning and is in effect for the western side of the northern and central Sacramento Valley and adjacent elevations below 3000 feet Tuesday morning into the evening. .Discussion... No big changes to forecast with main impacts coming from first critical fire weather conditions expected late Monday night through Wednesday. Also, no changes really for the heat risk starting on Tuesday through the end of the week...of course including July 4th. Tonight and Sunday...very good agreement with ensemble data a trough will push across the Pacific Northwest with the southern weaker end of it across Northern California. No real instability and lift to worry about for thunderstorms for our area. This trough will keep the temperatures on the not hot side through Sunday. That trough then pushes out into Montana and allows the mid level flow to turn from the northwest. This will cause typical breezy conditions in the valley as well as very very dry air Tuesday and Wednesday. In respect to fire weather conditions burning index and ERC values will be near record values for this time of the year and when combined with the hot temperatures and very poor relative humidities in the single digits in the day and recovery only into the teens and 20s...we went ahead and upgraded the fire weather watch to a red flag warning. The worse conditions look to be in the lower elevations....below 3000 feet during those times. In regards to the heat. Confidence in hot conditions has increased further for Tuesday and Wednesday with the NBM spread on maximum temeratures very small both those days. Most valley locations will be pushing 110 degrees. ECMWF EFI data also showing high values and some lower shift of tail values to support it. With this in mind we also upgraded the excessive heat watch to a warning starting Tuesday. HeatRisk has large area of major conditions and good chunk of area in extreme heatrisk values. && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday)... In the extended...ensemble and cluster data showing the strong upper level ridge to slide over the top of California to keep the heat going. NBM and EC ensemble data are suggesting a very slight possible cooling Thursday and Friday...but not much keeping temperatures from 100 to 110 across most of the valley. Certainly less confidence that far out and if needed we may be able to tweak the current excessive heat warning a bit in the Delta and Sacramento valley but looking at location of ridge and strength of it leaning to side of hotter right now makes sense to issue the excessive heat warning out this far. Rasch && .AVIATION... VFR conditions next 24 hours. Surface wind mainly below 12 knots except vicinity west Delta southwesterly local gusts 15-25 kts. Local northwesterly wind gusts 15-20 kts across the northern Sacramento Valley 00z-12z Sunday. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 11 PM Monday to 8 PM PDT Wednesday for Carquinez Strait and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft- Eastern Mendocino NF-Eastern Portion of Shasta/Trinity NF- Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units-Southeast Edge Shasta- Trinity NF and Western Portions of Tehama-Glenn Unit-Southern Sacramento Valley in Yolo-Sacramento Far Western Placer, southern Sutter and Solano County Below 1000 Ft. Excessive Heat Warning from 11 AM Tuesday to 8 PM PDT Saturday for Carquinez Strait and Delta-Central Sacramento Valley- Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley-Southern Sacramento Valley. && $$