411
FXUS66 KSTO 172007
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
107 PM PDT WED SEP 17 2025
FOR ADDITIONAL DETAILS ON WEATHER AND EXPECTED IMPACTS OVER THE
NEXT 7 DAYS, PLEASE VISIT WEATHER.GOV/STO/BRIEFING.
DISCUSSION
SYNOPSIS
REMNANTS OF TROPICAL SYSTEM MARIO WILL BEGIN IMPACTING THE AREA
LATER TOMORROW. THE SYSTEM WILL BRING A CHANCE OF RAIN TO THE
ENTIRE AREA THURSDAY NIGHT THROUGH EARLY SATURDAY. THERE WILL BE A
RISK OF A FEW THUNDERSTORMS WITH HEAVY RAIN MAINLY IN THE SIERRA
DURING THIS TIME. TEMPERATURES WILL BE MUCH COOLER THROUGH THE
WEEKEND. ANOTHER SYSTEM WILL APPROACH THE AREA NEXT WEEK AROUND
TUESDAY BRINING ANOTHER CHANCE OF PRECIPITATION.
KEY MESSAGES
* THURSDAY - SATURDAY:
- REMNANTS OF TROPICAL SYSTEM MARIO WILL BEGIN IMPACTING THE AREA
LATE THURSDAY AS IT MOVES FROM NORTH TO SOUTH.
- THERE WILL BE A BRIEF PERIOD OF FIRE WEATHER CONCERNS THURSDAY
EVENING AS A FEW THUNDERSTORMS MAY BE DRY BUT THE ATMOSPHERE IS
EXPECTED TO MOISTEN UP QUICKLY OVERALL DECREASING FIRE WEATHER
THREATS.
- THERE WILL ALSO BE A THREAT OF ISOLATED AREAS OF HEAVY RAIN IN
THE SIERRA THURSDAY NIGHT THROUGH SATURDAY MORNING. RAINFALL
AMOUNTS OF AROUND AN INCH WILL BE POSSIBLE WITH LOCALLY HIGHER
AMOUNTS. VALLEY AMOUNTS SHOULDN'T BE ON THE HEAVY SIDE BUT AN
ISOLATED THUNDERSTORM OR TWO WILL BE POSSIBLE IN THE VALLEY
ALSO. DESPITE THIS SYSTEM BEING PRETTY CLOSE, CONFIDENCE IS
STILL FAIRLY LOW ON THE DETAILS SO CHECK AN EYE OUT FOR
UPDATES.
* TUESDAY
- LOW CONFIDENCE (20-30%) OF ANOTHER WEATHER SYSTEM MOVING ACROSS
THE AREA NEXT WEEK. RIGHT NOW BEST CHANCE OF THAT IS TUESDAY
BUT CONFIDENCE IS FAIRLY LOW SO TUNE IN FOR UPDATES ON THIS AS
WELL.
CHANGES FROM PREVIOUS FORECAST
- UPTICK IN AMOUNT OF RAIN EXPECTED, WITH BIGGEST CHANGES IN THE
SIERRA.
AVIATION
VFR CONDITIONS AND CLEAR SKIES EXPECTED AT INTERIOR NORTHERN
CALIFORNIA TAF SITES NEXT 24 HOURS. SURFACE WINDS GENERALLY LESS
THAN 12 KTS.
STO WATCHES/WARNINGS/ADVISORIES
NONE.
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