471  
FXUS66 KSTO 272116  
AFDSTO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SACRAMENTO CA  
216 PM PDT SAT MAY 27 2023  
   
SYNOPSIS
 
 
ISOLATED TO SCATTERED THUNDERSTORM CHANCES CONTINUE FOR THE  
MOUNTAINS, MAINLY NORTHERN FOOTHILLS, AND NORTHERN HALF OF THE  
SACRAMENTO VALLEY THROUGH THE HOLIDAY WEEKEND. THUNDERSTORM  
CHANCES CONTINUE NEXT WEEK OVER THE MOUNTAINS. TEMPERATURES WILL  
REMAIN NEAR OR SLIGHTLY BELOW NORMAL.  
 

 
   
DISCUSSION
 
 
LOW PRESSURE AREA OVER ALONG THE PACIFIC NORTHWEST COAST WILL  
DEEPEN ALONG THE COAST TO AROUND THE MENDOCINO COUNTY AREA  
TONIGHT. IN THE NEAR TERM SHOWERS AND THUNDERSTORMS MAY FORM OVER  
THE MOUNTAINS THIS AFTERNOON. ANY SHOWERS AND THUNDERSTORMS THAT  
DO FORM SHOULD MOVE EAST OF THE CREST LATE THIS AFTERNOON TO  
EARLY EVENING. THE FOCUS THEN BECOMES THE NORTHERN HALF OF THE  
FORECAST AREA FOR THE OVERNIGHT HOURS. MAIN FOCUS WILL BE FROM  
BUTTE COUNTY TO NORTHERN LAKE COUNTY NORTHWARD IN THE VALLEY AND  
THE SURROUNDING MOUNTAINS. ACTIVITY LOOKS TO INCREASE IN THIS  
AREA DURING THE EVENING WITH THE POTENTIAL FOR SOME LATE NIGHT  
ACTIVITY WELL PAST MIDNIGHT. THUNDERSTORMS THAT FORM LOOK LIKE  
THEY WILL CONTAIN VERY HEAVY RAIN AND SMALL HAIL. PRECIPITABLE  
WATERS REMAIN VERY HIGH FOR THIS TIME OF YEAR OVER THE REGION  
THROUGH TUESDAY WITH THE HIGHEST TONIGHT DURING THAT TIME PERIOD.  
LOCAL FLOODING WITH THE STRONGER STORMS MAY BE POSSIBLE. AS THE  
LOW DROPS SOUTHWARD IT SHOULD HELP TO KEEP PORTIONS OF THE VALLEY  
BREEZY OVERNIGHT.  
 
ON SUNDAY THE CENTER OF THE LOW WILL MOVE TO OFF THE COAST OF THE  
BAY AREA. THUNDERSTORM ACTIVITY LOOKS LIKE IT MIGHT GET STARTED A  
LITTLE EARLIER IN THE DAY BY LATE MORNING TO EARLY AFTERNOON.  
THE FOCUS CONTINUES TO BE OVER THE MOUNTAINS WITH CHANCES  
CONTINUING FOR PORTIONS OF THE CENTRAL SACRAMENTO VALLEY  
NORTHWARD. VALLEY THUNDERSTORMS LOOK POSSIBLE BY MID AFTERNOON  
LASTING THROUGH EARLY EVENING. ANY THUNDERSTORMS WILL CONTINUE TO  
HAVE HEAVY RAIN WITH THEM BUT HAIL SIZE SHOULD INCREASE ON SUNDAY.  
 
ON MONDAY THE CENTER OF THE LOW WILL MOVE TO THE CENTRAL COAST AND  
CONTINUE TO MOVE SOUTHWARD INTO SOUTHERN CALIFORNIA ON TUESDAY.  
CONTINUED AFTERNOON AND EVENING THUNDERSTORMS BOTH DAYS. THESE  
TWO DAYS THUNDERSTORMS WOULD HAVE THE BEST CHANCE OF MAKING IT  
INTO THE MOTHERLODE BY LATE AFTERNOON OR EARLY EVENING.  
THUNDERSTORMS ARE EXPECTED TO MOVE TOWARDS THE FOOTHILLS THAT FORM  
OVER THE HIGHER ELEVATIONS. SLIGHT CHANCES CONTINUE EACH DAY FOR  
THE FAR NORTHERN END OF THE VALLEY AS WELL. ANY HOLIDAY TRAVELERS  
MAY WANT TO KEEP THE TIMING IN MIND.  
 
TEMPERATURES WILL GENERALLY BE BELOW NORMAL FOR THIS TIME OF  
YEAR THROUGH TUESDAY WHICH MAY HELP TO KEEP PEOPLE OUT OF THE  
WATER THIS HOLIDAY WEEKEND. RIVERS AND LAKES CONTINUE TO BE VERY  
COLD. WATER TEMPERATURES ARE MAINLY IN THE 50S FOR THE VALLEY  
TRANSITIONING TO THE 40S IN THE FOOTHILLS.  
 

   
EXTENDED DISCUSSION (WEDNESDAY THROUGH SATURDAY)
 
 
WEDNESDAY A TROUGH OF LOW PRESSURE WILL EITHER BE THROUGH  
CALIFORNIA OR JUST TO THE WEST WHILE A LOW PRESSURE AREA IS EITHER  
OVER SOUTHERN CALIFORNIA OR ARIZONA DEPENDING ON THE  
DETERMINISTIC MODELS. CLUSTERS INDICATE A WEAK TROUGH OVER THE  
REGION. ALL SEEM TO POINT TO CONTINUED AFTERNOON AND EVENING  
THUNDERSTORMS OVER THE MOUNTAINS REGARDLESS OF EXACT POSITIONING  
OF THE LOWS.  
 
THURSDAY IS WHEN THE MODELS DIVERGE SO CONFIDENCE BECOMES LOW THE  
NEXT FEW DAYS. LOW PRESSURE AREA WILL EITHER BE OVER CALIFORNIA OR  
THE PACIFIC NORTHWEST. WEAKER TROUGHING IS INDICATED BY THE  
CLUSTERS SO THERE MAY BE LESS MOUNTAIN THUNDERSTORM ACTIVITY.  
ENSEMBLES CONTINUE TO KEEP THUNDERSTORMS OVER THE CREST EXTENDING  
INTO THE SOUTHERN CASCADES AT THIS TIME. FRIDAY AND SATURDAY THERE  
WILL BE A LOW PRESSURE AREA IN THE GULF OF ALASKA BUT THE EXTENT  
OF HOW DEEP IT IS AT THIS TIME REMAINS UNCERTAIN. ENSEMBLES KEEP  
SOME AFTERNOON AND EVENING THUNDERSTORMS ACTIVITY FROM AROUND THE  
TAHOE REGION SOUTHWARD ALONG THE CREST. IT IS ALSO INDICATING  
A WARMING TREND TO NEAR NORMAL OR SLIGHTLY ABOVE TEMPERATURES  
LATE NEXT WEEK AND INTO THE WEEKEND.  
 

 
   
AVIATION
 
 
VFR CONDITIONS NEXT 24 HOURS EXCEPT FOR ISOLATED MVFR CONDITIONS  
POSSIBLE IN SHOWERS/THUNDERSTORMS, MAINLY OVER MOUNTAINS. GUSTY  
AND ERRATIC WINDS EXPECTED NEAR THUNDERSTORMS. SURFACE WIND  
GENERALLY AT OR BELOW 15 KTS EXCEPT VICINITY OF DELTA WITH  
SOUTHWESTERLY WIND UP TO 25 KNOTS.  

 
   
STO WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
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