Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
392 FXUS66 KSTO 132140 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 240 PM PDT Thu Jun 13 2024 .SYNOPSIS... Isolated shower/thunderstorms over the Sierra crest south of Highway 50 today. Critical fire weather conditions likely late Saturday night through Monday afternoon across the Sacramento Valley. && .DISCUSSION... Key Points - A Fire Weather Watch goes into effect 11 PM Saturday - 5 PM Monday across the majority of the Sacramento Valley due to low relative humidity, gusty north winds, and poor overnight recoveries. - 10-20% chance of shower/thunderstorm over the Sierra crest south of Highway 50 this afternoon. Short-Term Discussion (Today THROUGH Sunday)... No prescription needed! These skies are clearer than my natural, unaided vision. Current GOES-West satellite imagery shows mostly clear skies across interior Northern California this afternoon. Temperatures are roughly around 15 to 20 degrees cooler than this time yesterday morning, valid at 215 PM PDT. This cooldown is most noticeable in the central and northern Sacramento Valley. These cooler daytime highs will continue through Saturday as ridging shifts eastward and a low pressure area approaches over the Gulf of Alaska, with locally breezy onshore flow. There is also a slight (10-20%) probability of isolated shower/thunderstorms over the Sierra Crest south of Highway 50 this afternoon and evening. Over the weekend, increased northerly flow and minimum relative humidity in the low teens to low 20s will bring critical fire weather conditions to the Sacramento Valley. The National Blend of Models (NBM) suggests a 25-50% probability for wind gusts of 40 mph or higher, strongest on Sunday, and in the northern and central Sacramento Valley west of I-5. Daytime relative humidity is projected to be in the 10-20% range, with overnight recoveries in the 30-45% range Saturday and Sunday night. The gusty northerly winds and low relative humidity will likely lead to critical fire weather conditions late Saturday night through Monday afternoon. As a result a Fire Weather Watch has been issued and will go into effect 11 PM Saturday - 5 PM Monday for the majority of the Sacramento Valley. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Ensembles and clusters continue to show an upper level low dropping southeast from the Pacific Northwest into the Great Basin Region Monday through Wednesday. This will bring cooler temperatures and breezy winds to NorCal early next week. Ensembles continue show persistent northerly winds, which combined with afternoon relative humidity levels in the teens will likely lead to a continued period of enhanced fire weather concerns, especially over the northern Sacramento Valley. The forecast is currently dry, but can`t completely rule out any convection over northern Shasta County early next week. Temperatures gradually warm up next week, but uncertainty in how much remains uncertain. && .AVIATION... VFR conditions over interior NorCal next 24 hours. Southerly surface winds up to 20 kts in the southern Sacramento Valley, and northwesterly wind gusts up to 20 kts northern San Joaquin Valley until 06Z Friday. Surface winds 15-25 kts vicinity Delta with gusts up to 30 kts. && .STO WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from late Saturday evening through Monday afternoon 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-Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units- Northern Sierra Including Lassen NP and Plumas and Lassen NF/S West of the Sierra Crest (West of Evans Peak-Grizzly Peak- Beckworth Peak)-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. && $$