593
FXUS66 KSTO 131810
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1110 AM PDT THU AUG 13 2026
FOR ADDITIONAL DETAILS ON WEATHER AND EXPECTED IMPACTS OVER THE
NEXT 7 DAYS, PLEASE VISIT WEATHER.GOV/STO/BRIEFING.
KEY MESSAGES
- SHOWER AND THUNDERSTORM CHANCES SOUTH OF INTERSTATE 80 TODAY,
WITH BEST CHANCES SOUTH AND EAST OF OUR AREA.
- RED FLAG WARNING IN EFFECT UNTIL 9 PM TODAY FOR A MIX WET/DRY
THUNDERSTORMS AND STRONG OUTFLOW WINDS FOR ELEVATIONS ABOVE
5000 FEET IN THE SIERRA.
- NOTABLY COOLER THAN NORMAL TEMPERATURES FOR THE REMAINDER OF
THE WEEK AND INTO THE WEEKEND.
DISCUSSION
CUMULUS ARE BEGINNING TO DEVELOP ALONG THE SIERRA
CREST THIS MORNING, WITH THUNDERSTORM ACTIVITY POSSIBLE THIS
AFTERNOON (10-20% CHANCE ON THE WESTERN SIDE OF THE CREST, SOUTH
OF I-80). THUNDERSTORMS THAT DO DEVELOP ARE EXPECTED TO MOVE
EASTWARD, AND THE MAJORITY OF ACTIVITY IS ANTICIPATED FURTHER
SOUTH AND EAST. DUE TO THE POTENTIAL FOR WET AND DRY THUNDERSTORMS
WITH LIGHTNING AND (OF PRIMARY CONCERN) GUSTY OUTFLOW WINDS, A
RED FLAG WARNING REMAINS IN EFFECT UNTIL 9PM FOR THE SIERRA SOUTH
OF I-80 AND ABOVE 5000 FEET.
IN ADDITION TO THUNDERSTORM CHANCES, THE CURRENT PATTERN BRINGS
WELL BELOW NORMAL HIGH TEMPERATURES THROUGH THE WEEKEND. VALLEY
TEMPERATURES ARE EXPECTED TO BE IN THE 80S TODAY AND TOMORROW,
INCREASING SLIGHTLY OVER THE WEEKEND AND WARMING AGAIN THROUGHOUT
NEXT WEEK. THUNDERSTORM CHANCES DIMINISH SIGNIFICANTLY TOMORROW
(LESS THAN 10% EVERYWHERE), AND INTERIOR NORCAL THEN SETTLES INTO
A CALMER AND DRIER PATTERN WITH NEAR NORMAL TEMPERATURES WELL INTO
NEXT WEEK.
AVIATION
VFR CONDITIONS PREVAIL ACROSS INTERIOR NORCAL NEXT 24 HOURS.
BREEZY ONSHORE FLOW WILL CONTINUE TODAY, WITH SURFACE WINDS BELOW
15 KTS WITH GUSTS UP TO 25 KTS THIS AFTERNOON AND EVENING AS DELTA
BREEZE INCREASES. VALLEY WINDS LOWER AFTER 04Z FRIDAY BUT WILL
SEE CONTINUED 15-25 KT GUSTS OVER THE DELTA THROUGH 18Z FRIDAY.
MOUNTAIN THUNDERSTORM CHANCES CONTINUE THROUGH AROUND 03Z FRIDAY
WITH LINGERING 10-15% CHANCE ON FRIDAY.
STO WATCHES/WARNINGS/ADVISORIES
RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR SIERRA (CAL-
TUO) ABOVE 5000 FT-SIERRA (EL DORADO-AMADOR) ABOVE 5000 FT.
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