032 FXUS66 KSTO 222042 AFDSTOArea Forecast Discussion National Weather Service Sacramento CA 142 PM PDT Mon Sep 22 2025
For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing.
.SYNOPSIS...
Brief ridging continues through tomorrow across northern California, with above normal temperatures and dry conditions. Moderate HeatRisk today, with widespread moderate HeatRisk and isolated major HeatRisk tomorrow. Increased chances for showers and thunderstorms Wednesday through Friday for areas along and south of I-80.
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.KEY MESSAGES...
* TODAY - TUESDAY:
- Above normal temperatures continue today and tomorrow, with moderate HeatRisk across the Sacramento Valley, San Joaquin Valley and Delta. Widespread moderate HeatRisk and isolated major HeatRisk Tuesday, with best chances in the southern Sacramento Valley, San Joaquin Valley and Delta.
- Breezy northerly winds today through tomorrow afternoon are expected within the northern Sacramento Valley. Chance for elevated fire weather concerns when low RH values co-locate with the breeze winds. Confidence however is low on this occurring.
* WEDNESDAY - FRIDAY:
- Temperatures cool Wednesday through the end of the week, with increased moisture and instability into the region.
- Weather system moves into the region bringing chances for showers and thunderstorms Wednesday through Friday, with the highest chances along and south of I-80, including the Valley from Sacramento southward.
- Confidence remains low in the evolution of the upper level wave that tracks through CA. Guidance struggles to determine the strength, track, and motion of the low as it moves through CA into the four corners region. A stronger low pressure would help increase rain/thunderstorm chances, while a weaker more open wave system would decrease our chances for showers and storms as we move into the weekend.
.AVIATION...
VFR conditions prevail through the TAF period, with light northerly winds for each TAF site. Skies remain SKC to FEW this evening and overnight, with winds going light and variable for the Sacramento Metro region. Winds turn back toward the north around sunrise tomorrow for each site under SKC.
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.STO WATCHES/WARNINGS/ADVISORIES... None. &&
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NWS STO Office Area Forecast Discussion