973  
FXUS66 KSTO 272118  
AFDSTO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SACRAMENTO CA  
218 PM PDT WED OCT 27 2021  
   
SYNOPSIS
 
 
QUIETER WEATHER WITH DRY AND WARMER CONDITIONS THROUGH LATE WEEK.  
SHOWER CHANCES FRIDAY INTO SATURDAY IN FAR NORTHERN CALIFORNIA,  
THEN AGAIN EARLY NEXT WEEK FOR THE MAJORITY OF NORTHERN  
CALIFORNIA.  
 

 
   
DISCUSSION
 
 
VISIBLE SATELLITE IMAGERY SHOWS CLOUD COVER CONTINUING TO BLANKET  
THE FAR NORTH STATE THIS AFTERNOON AS SOME WEAK MOISTURE STREAMS  
OVER THE UPPER LEVEL RIDGE BUILDING OVER CALIFORNIA. THIS RIDGING  
WILL BRING DRY WEATHER AND WARMER TEMPERATURES THE NEXT COUPLE OF  
DAYS. EXPECT VALLEY TEMPERATURES NEAR 70 TO 75 DEGREES THROUGH  
FRIDAY WITH THE MOUNTAINS AND FOOTHILLS IN THE 40S TO 60S. CLEAR  
SKIES THROUGH MOST OF THE VALLEY WILL ALLOW FOR PATCHY FOG TO  
DEVELOP TOMORROW MORNING, AS INDICATED BY HREF, WITH THE BEST  
CHANCES NEAR AND SOUTH OF THE CHICO AREA.  
 
ENSEMBLE GUIDANCE INDICATES A TROUGH APPROACHING THE WEST COAST  
FRIDAY IS LIKELY TO SPLIT AS IT REACHES THE COAST. THE NORTHERN  
PORTION WILL MOVE THROUGH THE PACNW WHILE THE SOUTHERN PORTION  
MOVES THROUGH NORTHERN CALIFORNIA. UNCERTAINTY REMAINS BETWEEN  
ENSEMBLES IN TIMING AND STRENGTH OF THIS TROUGH. ROUGHLY HALF OF  
THE 500MB CLUSTERS INDICATE IT WILL BECOME A CUTOFF LOW BEFORE  
REACHING LAND WHILE THE OTHERS INDICATE A WAVE. AT THIS POINT, IT  
LOOKS LIKE THE TROUGH WILL MOVE INTO THE AREA FRIDAY INTO  
SATURDAY, THOUGH EXACT TIMING OF THE FRONT AND ASSOCIATED  
PRECIPITATION IS STILL UNCERTAIN. IT WILL BRING SHOWERS WITH A  
SLIGHT CHANCE OF THUNDERSTORMS MAINLY TO THE COASTAL RANGE, NORTHERN  
SACRAMENTO VALLEY, AND SOUTHERN CASCADES. QPF IS FORECAST TO  
REMAIN LESS THAN 0.25 INCH, WITH LOCALLY HIGHER AMOUNTS IN  
THUNDERSTORMS. TEMPERATURES WILL COOL WITH THIS WEATHER SYSTEM ON  
SATURDAY WITH VALLEY TEMPERATURES BACK IN THE MID TO UPPER 60S AND  
40S TO LOW 60S IN THE MOUNTAINS AND FOOTHILLS. -HEC  
 

 
   
EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)
 
 
DRY WEATHER RETURNS SUNDAY WITH PARTLY CLOUDY SKIES AHEAD OF AN  
APPROACHING PACIFIC TROUGH. TEMPERATURES ARE FORECAST TO BE NEAR  
TO SLIGHTLY BELOW AVERAGE FOR THIS TIME OF YEAR WITH HIGHS IN THE  
60S FOR THE VALLEY AND 40S TO 50S IN THE MOUNTAINS. BY THE  
OVERNIGHT HOURS, THE LOW PRESSURE SYSTEM IS EXPECTED TO MOVE  
ONSHORE AND BRING SHOWER CHANCES TO THE REGION INTO EARLY NEXT  
WEEK. EXPECTED PRECIPITATION AMOUNTS REMAIN UNCERTAIN DUE TO SOME  
DISCREPANCIES IN LOCATION OF THE TROUGH IN ENSEMBLE SOLUTIONS AS  
PRESENTED IN CLUSTER ANALYSIS. TIMING HAS BETTER AGREEMENT WITH  
INTERIOR NORTHERN CALIFORNIA POSSIBLY SEEING WET WEATHER RETURN BY  
MONDAY MORNING. STAY TUNED FOR UPDATES AS WE GET CLOSER TO NEXT  
WEEK AND MODELS COME INTO BETTER AGREEMENT ABOUT THE EXPECTED  
DETAILS OF THIS WEATHER SYSTEM.  
 

 
 

 
   
AVIATION
 
 
VFR CONDITIONS EXPECTED INTO THE OVERNIGHT AT THE TAF SITES.  
PATCHY FOG AND MVFR WILL BE POSSIBLE BETWEEN 13 AND 17Z MAINLY IN  
THE SAN JOAQUIN VALLEY. WIND REMAIN UNDER 12 KNOTS.  
 

 
   
STO WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
 
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