968
FXUS66 KSTO 112039
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
139 PM PDT SUN OCT 11 2026
FOR ADDITIONAL DETAILS ON WEATHER AND EXPECTED IMPACTS OVER THE
NEXT 7 DAYS, PLEASE VISIT WEATHER.GOV/STO/BRIEFING.
KEY MESSAGES
- RED FLAG WARNING IN EFFECT UNTIL 5 AM MONDAY DUE TO GUSTY
NORTH WINDS AND LOW RELATIVE HUMIDITY FOR NORTHERN SACRAMENTO
VALLEY AND ADJACENT FOOTHILLS.
- COOLER TEMPERATURES, MOUNTAIN SHOWERS AND ISOLATED
THUNDERSTORMS TODAY AND MONDAY.
- POTENTIAL FOR FIRST MEASURABLE SNOW OF THE SEASON IN THE
SIERRA LATE TONIGHT- MONDAY, SOUTH OF US 50 AND ABOVE 6500
FEET.
- DRY WEATHER AND BELOW-NORMAL TEMPERATURES ON TUESDAY,
FOLLOWED BY DRYING AND WARMING TREND MID- TO LATE NEXT WEEK.
DISCUSSION
..TODAY AND MONDAY
A CLOSED LOW WILL CONTINUE TO DIG SOUTHWARD FROM THE PACIFIC NW
AND NORTHERN CALIFORNIA INTO MONDAY, WITH THE CENTER HANGING OVER
THE EAST-CENTRAL OREGON. NORTHERLY WINDS PEAKED UP ALONG THE
SACRAMENTO VALLEY AND ADJACENT FOOTHILLS THIS MORNING, WHERE GUSTS
UP TO 40 MPH WAS OBSERVED. WINDS ARE EXPECTED TO SLIGHTLY
DIMINISH THIS AFTERNOON, BUT WILL REMAIN BREEZY WITH GUSTS FROM
25-35 MPH INTO MONDAY WITH THE STRONGEST WINDS ALONG AND
WEST OF THE I-5 CORRIDOR. THESE GUSTY WINDS COMBINED WITH DAYTIME
RELATIVE HUMIDITY AROUND 15-25 PERCENT ARE PROMOTING CRITICAL FIRE
WEATHER CONDITIONS FOR PORTIONS OF THE NORTHERN SACRAMENTO VALLEY
AND ADJACENT FOOTHILLS. A RED FLAG WARNING REMAINS IN EFFECT
UNTIL 5 AM MONDAY DUE TO GUSTY NORTH WINDS AND LOW RELATIVE
HUMIDITY FOR NORTHERN SACRAMENTO VALLEY AND ADJACENT FOOTHILLS.
A SHORTWAVE TROUGH EMBEDDED TO THE AFOREMENTIONED LOW WILL TRAVERSE
THE AREA TODAY INTO MONDAY. DRY WEATHER CONDITIONS IS EXPECTED
TODAY, WITH ISOLATED SHOWERS POSSIBLE OVER THE SIERRA CREST SOUTH
OF THE US-50 THIS AFTERNOON AND EVENING. THERE IS AN INCREASING
CHANCE OF MOUNTAIN SHOWERS TONIGHT THROUGH MONDAY, ESPECIALLY ALONG
THE SIERRA. SOME CAMS ARE SHOWING ISOLATED NOCTURNAL CONVECTION
MOVING ACROSS THE AREA FROM THE SOUTH- SOUTHWEST LATE TONIGHT INTO
MONDAY. COLDER AIR ALOFT WILL BRING SOME SHALLOW INSTABILITY LATE
TONIGHT AND MONDAY, CAPABLE OF PRODUCE BRIEF HEAVY DOWNPOURS AND
A CHANCE OF ISOLATED THUNDERSTORMS. RAINFALL TOTAL AMOUNTS
FORECAST ARE TRENDING LOWER WITH A FEW HUNDREDTHS TO QUARTER OF AN
INCH FOR THE SIERRA, WITH THE HIGHEST AMOUNTS SOUTH OF I-80.
THIS SYSTEM WILL BRING THE FIRST MEASURABLE SNOWFALL OF THE
SEASON IN THE SIERRA SUNDAY NIGHT TROUGH MONDAY. SNOW LEVELS ARE
EXPECTED TO BE ABOVE 7500 FEET LOWERING TO 6000-7000 FEET LATE
TONIGHT INTO MONDAY, RISING TO 7500 FEET MONDAY AFTERNOON
LOWERING TO AS LOW AS 5500 FEET MONDAY NIGHT. AS THE SNOW LEVELS
LOWER, PRECIPITATION ALSO DIMINISH. RESULTING IN INCREASING
UNCERTAINTY ON THE EXACT SNOW AMOUNTS.
..TUESDAY-SATURDAY
HIGH PRESSURE AND UPPER-LEVEL RIDGE WILL BUILD IN QUICKLY IN THE
WAKE OF THE AFOREMENTIONED CLOSED LOW TRANSLATING EASTWARD. ANY
LINGERING MOUNTAIN SHOWERS ARE EXPECTED TO DISSIPATE TUESDAY
MORNING AS DRIER AIRMASS MOVES IN. GENERALLY DRY WEATHER, WITH
CONTINUING BELOW NORMAL TEMPERATURES IS EXPECTED ON TUESDAY.
ENSEMBLE MEMBERS ARE IN A GOOD AGREEMENT WITH THE UPPER-LEVEL
RIDGE CONTINUE BUILDING ON WEDNESDAY, BEFORE AMPLIFY AND BRING
ABOVE -AVERAGE 500 MB HEIGHTS OVER THE WESTERN CONUS THURSDAY AND
FRIDAY. THIS WILL BRING A DRIER AND WARMING TREND ACROSS NORTHERN
INTERIOR CALIFORNIA, WITH HIGH TEMPERATURES BACK TO THE 80S. BREEZY
NORTH TO NORTHEAST WINDS ARE ANTICIPATED FOR THE SACRAMENTO
VALLEY AND ADJACENT FOOTHILLS, AND TO THE SIERRA THURSDAY AND
FRIDAY. THERE IS A POTENTIAL FOR ELEVATED FIRE WEATHER CONDITIONS
DUE TO BREEZY NORTH WINDS AND LOW RELATIVE HUMIDITY IN THE TEENS
OVER THE SACRAMENTO VALLEY AND ADJACENT FOOTHILLS.
AVIATION
VFR CONDITIONS CONTINUE ACROSS INTERIOR NORCAL NEXT 24
HOURS. NORTH TO NORTHEAST WINDS 10 TO 20 KTS, WITH 25 TO 35 KT
GUSTS ALONG INTERSTATE 5, NORTH OF INTERSTATE 80 AND ACROSS
SHASTA COUNTY, WEAKENING AFTER 12Z MONDAY. ELSEWHERE, WEST-
SOUTHWEST WINDS THIS AFTERNOON WITH GUSTS UP TO 15 KTS UNTIL 03Z
MONDAY WITH LINGERING BREEZY SOUTH WINDS OVERNIGHT FOR THE
NORTHERN SAN JOAQUIN.
STO WATCHES/WARNINGS/ADVISORIES
RED FLAG WARNING UNTIL 5 AM PDT MONDAY FOR CENTRAL GLENN CO &
INTERSTATE 5-N. SAC VALLEY IN TEHAMA COUNTY-SHASTA METRO.
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