Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
805 FXUS66 KSTO 102120 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 220 PM PDT Wed Jul 10 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 into early next week. && Key Points - Long-duration, dangerous heat event persists this week. - Very hot today into Friday, followed by some cooling over the weekend into next week .Discussion... Ensembles show the upper high strengthening and building back westward towards interior NorCal, with very hot temperatures continuing through late week. This will result in widespread Major to Extreme HeatRisk across the Valley and foothills, with Major HeatRisk over the mountains through late week. Highs will peak on Thursday, with NBM probabilities depicting 85-100% chance of highs greater than 105 deg F in the Valley. Valley highs will range from 105 to 115 degrees through Friday. Limited overnight relief is expected with lows mainly in the upper 60s to lower 80s. An Excessive Heat Warning remains in effect for the Valley and foothills until 8 PM Friday. Additionally, a Heat Advisory remains in effect for the Delta, Sierra, southern Cascades, and Burney Basin until 8 PM Friday. Ensembles and clusters show the upper high pressure system shifting to the Four Corners region and an offshore low nudging towards the Central CA coast, allowing for a gradual cooling trend over the weekend as onshore flow increases. However, Saturday Valley highs will range from 100 to around 110, with some areas of Major to Extreme HeatRisk in the Valley and foothills. Moisture surging northward will support a slight chance of an afternoon shower/thunderstorm over higher elevations of the Sierra Nevada, with best chances occurring on Saturday. NBM indicates a 10-25% probability of thunderstorm development over the Sierra crest Saturday afternoon and evening, mainly south of I-80. Any thunderstorms that develop could be capable of gusty winds, and possible fire starts due to lightning. Latest HeatRisk: wpc.ncep.noaa.gov/heatrisk/ Heat Safety Tips: weather.gov/safety/heat && .EXTENDED DISCUSSION (Sunday THROUGH Wednesday)... Ensembles and clusters show the upper high pressure system shifting to the Four Corners region and an offshore upper low nudging towards the Central CA coast, allowing for a gradual cooling trend next weekend as onshore flow increases. The NBM depicts lightly cooler temperatures are still on track for Sunday- Wednesday, with mid 90s to around 104 deg F in the Valley and some lingering areas of Moderate HeatRisk. This cooling trend is expected to continue through mid-week, however, temperatures will remain a few degrees above normal through Wednesday. && .AVIATION... VFR conditions over interior NorCal for the next 24 hrs. Surface wind mainly below 12 kts except in the vicinity of the Delta where there will be southwesterly surface wind around 15-20 kts at times. && .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. && $$