858
FXUS66 KSTO 052149
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
249 PM PDT FRI SEP 5 2025
FOR ADDITIONAL DETAILS ON WEATHER AND EXPECTED IMPACTS OVER THE
NEXT 7 DAYS, PLEASE VISIT WEATHER.GOV/STO/BRIEFING.
DISCUSSION
SYNOPSIS
A PATTERN CHANGE WILL BRING A CONTINUED COOLING TREND INTO EARLY
NEXT WEEK, WITH CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS.
SMOKE FROM RECENT FIRE STARTS MAY IMPACT LOCAL AIR QUALITY.BREEZY
ONSHORE WINDS ARE POSSIBLE AT TIMES. HUMIDITY LEVELS WILL TREND
HIGHER INTO NEXT WEEK, WITH GOOD OVERNIGHT RECOVERIES.
KEY MESSAGES
* TODAY:
- HIGH TEMPERATURES CONTINUE ON A GRADUAL COOLING TREND WITH
WIDESPREAD MINOR TODAY AND TOMORROW
- SMOKE FORM RECENT FIRE STARTS WILL CONTINUE TO IMPACT AIR
QUALITY IN THE AREA. VISIT AIRNOW.GOV TO CHECK THE AIR QUALITY
INDEX FOR YOUR AREA.
* SATURDAY AND SUNDAY:
- MOSTLY CALM AND COOLER WEATHER IS EXPECTED ON SATURDAY AS AN
UPPER LEVEL TROUGH MOVES OUT OF THE AREA. HIGHER TEMPERATURES
WILL CONTINUE TO COOL INTO THE MID TO UPPER 80S, WITH MOSTLY
MID 80S FOR THE VALLEY BY SUNDAY.
- PRECIPITATION IN THE AREA WILL BE LIMITED TO SATURDAY
AFTERNOON/EVENING OVER THE NORTHWESTERN PORTION OF SHASTA
COUNTY, WHERE THERE WILL BE A SLIGHT CHANCE (15%) OF
THUNDERSTORMS.
- AN UPPER LEVEL LEVEL LOW DEVELOPING OFF THE PACIFIC NORTHWEST
COAST BY SUNDAY WILL REMAIN SLIGHTLY OFFSHORE AND WILL HELP
ENHANCE ONSHORE FLOW, WITH PERIODS OF BREEZY WINDS IN THE DELTA
AND VICINITY.
- SUNDAY LATE EVENING/OVERNIGHT SHOWER CHANCES IN THE NORTHERN
COASTAL RANGE AND NORTHERN SACRAMENTO VALLEY. DAYTIME HUMIDITY
LEVELS SURGE INTO THE MID 30S TO MID 40S ACROSS THE VALLEY,
WITH DECREASING FIRE WEATHER CONCERNS.
* MONDAY - THURSDAY:
- PRECIPITATION CHANCES CONTINUE ON MONDAY - THURSDAY AS AN UPPER
LEVEL TROUGH IS FORECAST TO MOVE INLAND OVER NORCAL.
- MONDAY PRECIPITATION CHANCES ARE HIGHS IN THE NORTHERN
SACRAMENTO VALLEY AND ADJACENT HIGHER ELEVATIONS.
- FORECAST DETAILS WILL LIKELY CHANGE OVER THE NEXT FEW DAYS,
ESPECIALLY SPECIFIC RAINFALL AMOUNTS.
- UNCERTAINTY PARTICULARLY EXISTS ON THUNDERSTORM FORMATION
- ENSEMBLES CONFIDENCE REMAINS HIGH ON THE OVERALL UPPER LEVEL
PATTERN.
- AVAILABLE MOISTURE WILL BE THE LIMITING FACTOR
- CURRENTLY, MOSTLY SCATTERED LIGHT RAIN SHOWERS WITH A FEW
EMBEDDED THUNDERSTORMS SEEMS MOST LIKELY; A GREAT DEAL OF
UNCERTAINTY REMAINS ON TOTAL AMOUNTS. AREAS IN THE NORTHERN
SACRAMENTO VALLEY, ADJACENT SOUTHERN CASCADES NORTHERN SIERRA
AND NORTHERN COAST RANGE STAND THE BEST CHANCES TO SEE
MEASURABLE PRECIPITATION AT THIS TIME.
- NBM PROBABILITIES FOR 0.25" OF RAIN ARE AROUND 30-50% FOR THE
LIKELY AREAS PREVIOUSLY MENTIONED.
CHANGES FROM PREVIOUS FORECAST
- SLIGHT CHANCE (15%) FOR THUNDERSTORMS SATURDAY
AFTERNOON/EVENING FOR NORTHWESTERN SHASTA COUNTY.
AVIATION
VFR CONDITIONS ARE EXPECTED OVER THE NEXT 24 HOURS. GENERAL
AFTERNOON WINDS WILL BE 10-15 KTS ACROSS THE SACRAMENTO VALLEY
WITH GUSTS UP TO 15-25 KTS, STRONGEST IN THE DELTA UNTIL 03Z SAT
WITH LINGERING GUSTS THROUGH THE DELTA THROUGH 12Z FRI. CHANCES
FOR MARINE INTRUSION AGAIN WITH CLOUD CEILINGS 1-2 KFT ACROSS THE
DELTA AND PORTIONS OF THE SAC. VALLEY FROM 11Z TO 16Z SAT.
STO WATCHES/WARNINGS/ADVISORIES
NONE.
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