Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
398 FXUS66 KSTO 282039 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 139 PM PDT Fri Jun 28 2024 .SYNOPSIS... Seasonably warm temperatures and periodically breezy weather through the weekend. Widespread Major to Extreme HeatRisk next week with triple digits and very warm overnight lows. Breezy north winds and low humidity will bring fire weather concerns to portions of the Sacramento Valley and adjacent foothills early next week. && Key Points - Long-duration, major heat event next week impacting holiday outdoor events. - An Excessive Heat Watch remains in effect for the Valley, Delta and foothills from Tuesday morning through Friday evening. - A Fire Weather Watch has been issued for the western side of the northern and central Sacramento Valley and adjacent elevations below 3000 feet Tuesday morning into the evening. - Elevated to critical fire weather conditions Monday through Wednesday. .Discussion... Modest warming trend expected through the weekend as the upper trough weakens over NorCal allowing high temperatures in the Valley to inch back toward the century mark. Marine layer remains shallow (less than 1k ft deep), but enough to bring some local breezes and overnight cooling to the Delta and southern Sacramento Valley. A short wave is expected to clip far northern California on Sunday. Thunderstorm threat will likely remain outside of the forecast area, with the latest NBM depicting less than 10% probability of thunderstorm development. Ensembles and clusters depict strong, anomalous ridging building into NorCal from the eastern Pacific next week. By Monday, daytime temperatures will be in the 100 to 105 range across the Valley. This will result in widespread Moderate HeatRisk. Areas of breezy north wind and low humidity are expected to result in critical fire weather conditions across portions of the northern and central Sacramento Valley and adjacent foothills early next week. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... A long-duration heat event is projected through the extended period as strong, anomalous ridging gradually builds across interior NorCal next week. Daytime highs will generally range from 100 to 110 F degrees across the Valley, Delta and foothills. NBM probabilities indicate a 20-60% chance of high temperatures greater than 110 F degrees across the northern Sacramento Valley Tuesday-Friday. Widespread Major to Extreme HeatRisk is expected starting Tuesday through at least Friday. This level of HeatRisk is very dangerous to anyone without proper hydration or adequate cooling. Strongly consider canceling outdoor activities. Little relief is expected overnight with lows forecast in the upper 60s to around 80, warmest in the northern Sacramento Valley and foothills. An Excessive Heat Watch remains in effect for the Valley, Delta, and foothills from Tuesday morning through Friday evening. Critical fire weather conditions are expected into Wednesday across portions of the northern and central Sacramento Valley and adjacent elevations below 3000 feet due to gusty northerly winds and low humidity. The strongest winds are expected on Tuesday, with gusts ranging from 20-30 mph. A Fire Weather Watch has been issued for the western side of the northern and central Sacramento Valley and adjacent elevations below 3000 feet Tuesday morning into the evening. && .AVIATION... VFR conditions over interior NorCal next 24 hours. Surface wind mainly below 12 knots except vicinity of Delta southwesterly surface wind gusts up to 20 kts at times. && .STO WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from late Monday night through Tuesday evening for Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft-Southeast Edge Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit. Excessive Heat Watch from Tuesday morning through Friday evening 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. && $$