998 FXUS66 KSTO 020025 AAA AFDSTO Area Forecast Discussion...UPDATED National Weather Service Sacramento CA 525 PM PDT Sun Jun 1 2025 For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing. .Discussion... .Synopsis... A Red Flag Warning is in effect for the Northern and Central Sacramento Valley and into the Coastal Range on Monday from low humidity and gusty winds. Otherwise, warm and dry weather is expected to persist today into next week alongside periodically breezy winds. Lastly, 5-15% PM mountain shower/thunderstorm chances are anticipated today and Wednesday-Thursday, primarily along the Sierra south of Highway 50 but no major impacts expected at this time. && .Key Messages... * Today - Monday: -Near normal highs today with gradual warming and areas of Moderate HeatRisk returning by Monday. -Elevated fire weather concerns this evening. -Critical fire weather conditions develop early Monday morning and continue into the evening across the northern and central Sacramento Valley and adjacent northern Coastal Range. --Low relative humidity with limited overnight recovery expected as breezy north winds increase Sunday evening. --Probability of wind gusts > 30 mph: 50-95%, highest within northern Sacramento Valley and adjacent Coastal Range. -Slight shower or thunderstorm chances around 5-15% across Shasta County mountains this evening, returning to portions of the Sierra south of Highway 50 on Monday. * Tuesday - Friday: -Broad northwesterly flow aloft expected to persist through the week with some increasing heights aloft. -Periodically breezy winds expected to continue within this flow pattern as temperatures settle slightly above normal with areas of Moderate HeatRisk. -Probability of Valley high temperatures > 95F: --Northern/Central Sacramento Valley: 60-90% --Delta, S. Sacramento Valley, N. San Joaquin Valley: 20-40% -Slight thunderstorm chances around 5-15% Wednesday PM and Thursday PM along the Sierra south of Highway 50. .Changes from previous forecast... -Red Flag Warning has been issued over the northern and central Sacramento Valley and adjacent northern Coastal Range from 2 am to 8 pm Monday. && .AVIATION... VFR conditions prevail over interior NorCal next 24 hours. Surface winds around 10-15 kts, with gusts up to 20 kts from 20z to 06z Mon. in the Valley and up to 25 kts across the Delta. Breezy winds linger over the Northern Sac. Valley with north winds 10 to 20 kts and gusts up to 20-30 kts from 09z Mon. through 18z Mon. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 2 AM to 8 PM PDT Monday for 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-Southeast Edge Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit. && $$