874
FXUS66 KSTO 071906
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1206 PM PDT WED OCT 7 2026
FOR ADDITIONAL DETAILS ON WEATHER AND EXPECTED IMPACTS OVER THE
NEXT 7 DAYS, PLEASE VISIT WEATHER.GOV/STO/BRIEFING.
KEY MESSAGES
- HEAT ADVISORY NOW IN EFFECT TILL 10 PM THURSDAY FOR THE
SACRAMENTO VALLEY, DELTA, NORTHERN SAN JOAQUIN VALLEY, AND
ADJACENT FOOTHILLS.
- WIDESPREAD MODERATE HEATRISK WITH AREAS OF MAJOR HEATRISK
THROUGH THURSDAY FOR THE DELTA, VALLEY, AND FOOTHILLS.
- CONFIDENCE IS INCREASING FOR A COOLING TREND OVER THE
WEEKEND, WITH SOME POTENTIAL FOR UNSETTLED WEATHER.
DISCUSSION
..TODAY & THURSDAY
UPPER LEVEL RIDGING CONTINUES TO DOMINATE THE SYNOPTIC PATTERN
ACROSS INTERIOR NORCAL THIS MORNING. HIGH PRESSURE ALOFT WILL
REMAIN THE PRIMARY DRIVER FOR OUR HOT TEMPERATURES AND LIGHT
SURFACE WINDS THROUGH THURSDAY, WITH HIGHS EXPECTED TO BE IN THE
MID TO UPPER 90S WITH SOME TRIPLE-DIGIT READINGS CONTINUING.
MODERATE HEATRISK AND AREAS OF MAJOR HEATRISK ALSO CONTINUE TODAY
AND THURSDAY. SYNOPTIC PATTERN WILL BEGIN TO BREAK DOWN BY EARLY
FRIDAY HOWEVER, USHERING IN COOLER TEMPERATURES AND BREEZY TO
GUSTY WINDS.
..FRIDAY
UPPER LEVEL TROUGH IN THE PACNW, WITH A WEAK OFFSHORE LOW WILL
DEVELOP ON FRIDAY, USHERING IN LOWER HEIGHTS ALOFT AND INCREASING
ONSHORE FLOW. WHILE DAYTIME TEMPERATURES WILL STILL BE 6 TO 12
DEGREES ABOVE NORMAL, THE OVERNIGHT RELIEF WILL HELP MITIGATE THE
HEATRISK FOR MUCH OF THE AREA. POCKETS OF MODERATE HEATRISK WILL
REMAIN IN THE THERMAL BELTS OF THE FOOTHILLS, BUT WITH THE
DOWNWARD TREND OF HEATRISK WE HAVE REMOVED FRIDAY FROM THE CURRENT
HEAT ADVISORY AND IT WILL NOW END AT 10 PM ON THURSDAY. ONSHORE
FLOW WITH WINDS GUSTING UP TO 30 MPH FRIDAY EVENING/NIGHT WILL
CERTAINLY PROVIDE A BREAK FROM THE SUMMER LIKE HEAT.
..SATURDAY - MONDAY
THIS WEEKEND WE WILL START TO SEE THE TRUE PATTERN CHANGE AND THE
RESULTANT SENSIBLE WEATHER EFFECTS. BY SATURDAY, PACNW TROUGHING,
WEAK OFFSHORE LOW, AND REMNANTS OF HURRICANE RACHEL WILL BEGIN TO
MERGE ACROSS OUR REGION AND PUSH ONSHORE. BREEZY TO GUSTY ONSHORE
WINDS SATURDAY MORNING ARE POSSIBLE, CLOUD COVERAGE, INCREASED
DAYTIME HUMIDITY VALUES WILL LEAD TO COOLER HIGH TEMPERATURES
AROUND THE AREA, WITH HIGHS IN THE UPPER 70S TO LOW 80S (WARMEST
IN THE NORTHERN SAN JOAQUIN VALLEY). BY SUNDAY, AN AREA OF LOW
PRESSURE SHOULD FORM OVER THE REGION, TRACK CLOSE TO THE COAST,
CONTINUING TO PROVIDE LOCALLY BREEZY WINDS WITH FURTHER COOLING,
AS HIGHS ARE FORECAST TO BE IN THE LOW TO MID 70S. RECENT NBM
MODEL RUNS CONTINUE TO SUGGEST ENOUGH MOISTURE FROM THE REMNANTS
OF HURRICANE RACHEL WILL ADVECT INTO THE AREA, BRINGING SHOWER
CHANCES AND A LESS THAN 10% CHANCE FOR THUNDERSTORMS DEVELOPING
MAINLY OVER THE MOUNTAINS. NORTH WINDS WILL ALSO DEVELOP IN THE
VALLEY, WITH GUSTS FORECAST TO BE AROUND 25-35 MPH.
SIMILAR WEATHER CONDITIONS WILL CONTINUE INTO MONDAY AS WELL, WITH
HIGHS IN THE LOW TO MID 70S, COOLER UPPER 50S TO MID 60S IN THE
HIGHER ELEVATIONS. CURRENTLY HAVE A NON-ZERO CHANCE OF SEEING SOME
ACCUMULATING SNOW, MAINLY SOUTH OF HWY-50 MONDAY MORNING, BUT NOT
EXPECTING SIGNIFICANT IMPACTS AT THIS TIME. LOW PRESSURE MOVES
FURTHER ONSHORE MONDAY AFTERNOON AND BEGINS TO MOVE EASTWARD AND
OUT OF THE AREA BY TUESDAY NIGHT, WHERE UPPER LEVEL RIDGING WILL
BEGIN TO BUILD OVER THE REGION.
THERE IS STILL A HIGH LEVEL OF UNCERTAINTY REGARDING MOISTURE,
THUNDERSTORMS, OVERALL WIND SPEEDS, AND POTENTIAL IMPACTS TO THE
REGION THIS WEEKEND AND INTO EARLY NEXT WEEK. BIGGEST QUESTION AT
THIS TIME WILL BE HOW MUCH MOISTURE ADVECTS INTO THE AREA, WILL IT
MAKE IT INTO LOWER ELEVATIONS, AND HOW MUCH CAN PRECIPITATION
COULD WE GET. UNCERTAINTY REGARDING WIND GUSTS SPEEDS IS HIGH AS
WELL FOR SATURDAY MORNING IN THE DELTA, THEN SUNDAY AND MONDAY IN
THE NORTHERN SACRAMENTO VALLEY. WE CAN SAY CONFIDENTLY A PATTERN
CHANGE IS GOING TO OCCUR, WE JUST ARE STILL HIGHLY UNCERTAIN ON
THE PRECIPITATION AND WIND IMPACTS AT THIS TIME.
AVIATION
VFR CONDITIONS PREVAIL ACROSS INTERIOR NORCAL NEXT 24 HOURS, WITH
LIGHT SURFACE WINDS GENERALLY BELOW 12 KNOTS. EAST WIND GUSTS UP
TO 15 TO 20 KNOTS IN THE HIGHER ELEVATIONS THROUGH 17Z THURSDAY.
STO WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 10 PM PDT THURSDAY FOR BUTTE COUNTY BELOW
1000 FT-C. SAN JOAQUIN COUNTY INCLUDING STOCKTON-C. SOLANO
COUNTY INCLUDING FAIRFIELD-C. STANISLAUS COUNTY INCLUDING
MODESTO-C. YOLO/NE SOLANO INCLUDING WOODLAND-CENTRAL COLUSA
COUNTY INCL. I-5-CENTRAL GLENN CO & INTERSTATE 5-CENTRAL
MOTHERLODE 1000-3000 FT-E. DIABLO RANGE ABOVE 1000 FT-EASTERN
COLUSA COUNTY-EASTERN GLENN COUNTY-N. MOTHERLODE 1000-3000 FT-N.
SAC VALLEY IN TEHAMA COUNTY-NE SAN JOAQUIN VALLEY BELOW 1000 FT-
SW SOLANO COUNTY INCLUDING VALLEJO-SAC METRO/W. EL DORADO/AMADOR
COUNTY-SACRAMENTO COUNTY DELTA-SAN JOAQUIN COUNTY DELTA-SHASTA
COUNTY FOOTHILLS 1000-3000 FT-SHASTA METRO-SIERRA (TEHAMA-
PLUMAS) 1000-3000 FT-SOUTHERN MOTHERLODE 1000-3000 FT-
SUTTER/YUBA COUNTIES BELOW 1000 FT-TRACY TRIANGLE BELOW 1000 FT-
W TEHAMA CO FOOTHILLS 1000-3000 FT-W. GLENN/COLUSA FOOTHILLS
1000-3000 FT-W. SHASTA COUNTY 1000-3000 FT-W. STANISLAUS COUNTY
ABOVE 1000 FT & I-5-W. YOLO COUNTY INCLUDING CAPAY/I-505-YOLO /
SOLANO COUNTY HILLS.
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