137  
FXUS66 KSTO 221141  
AFDSTO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SACRAMENTO CA  
341 AM PST MON JAN 22 2018  
   
SYNOPSIS
 
 
PACIFIC STORM MOVES THROUGH BRINGING MAINLY LIGHT PRECIPITATION.  
A STRONGER SYSTEM IMPACTS THE AREA MID-WEEK INTO FRIDAY BRINGING  
MODERATE TO HEAVY RAIN, MOUNTAIN SNOW AND GUSTY WIND.  
 

 
   
DISCUSSION
 
 
THE FRONT HAS CONTINUED TO WORK ITS WAY SLOWLY SOUTHWARD ACROSS  
INTERIOR NORCAL OVERNIGHT. PRECIP PICKED UP AS A WEAK WAVE MOVED  
ONSHORE, AND SOME LIGHT TO MODERATE SNOW WILL CONTINUE ACROSS THE  
NORTHERN SIERRA INTO THE MORNING WITH ADDITIONAL SNOWFALL  
ACCUMULATIONS UP TO 4 INCHES LEADING TO CHAIN REQUIREMENTS ALONG  
I-80, SO A WINTER WEATHER ADVISORY HAS BEEN POSTED.  
 
FURTHER NORTH, PROFILER DATA INDICATES SNOW LEVELS HAVE RISEN  
ABOVE 3K FEET ACROSS SHASTA COUNTY AND TRAFFIC CAMERAS SHOW WET  
ROAD SURFACES ALONG INTERSTATE 5 NORTH OF REDDING, SO THE WINTER  
WEATHER ADVISORY FOR THAT AREA HAS BEEN CANCELLED.  
 
PRECIP ALONG THE FRONT IS FORECAST TO TAPER DRAMATICALLY BY  
AFTERNOON AS UPSTREAM RIDGING MOVES IN. HOWEVER, MOISTURE WILL  
REMAIN TRAPPED BELOW THE SUBSIDENCE INVERSION SO CLOUDS WILL BE  
STUBBORN, PERSISTENT AND SLOW TO CLEAR FOR MUCH OF THE REGION.  
 
AFTER A BREAK, A STRONGER PACIFIC FRONTAL SYSTEM SPREADS INLAND  
OVER FAR NW CA TUESDAY NIGHT THEN ACROSS ALL OF INTERIOR NORCAL  
WEDNESDAY. BREEZY TO WINDY CONDITIONS DEVELOP AHEAD OF THE FRONT  
WEDNESDAY. MODELS CURRENTLY SHOW MORE SIGNIFICANT QPF WITH THIS  
STORM. SNOW LEVELS ATTM INITIALLY LOOK TO BE AROUND 5000 TO 6000  
FEET WEDNESDAY MORNING, BUT LOWER TO 2500 TO 3500 FEET WEDNESDAY  
NIGHT INTO THURSDAY IN POST-FRONTAL COLDER AMS. SHOWERY WEATHER  
PERSISTS THURSDAY.  
 

 
.EXTENDED DISCUSSION (FRIDAY THROUGH MONDAY)  
 
AREA OF HIGH PRESSURE WILL BRING MOSTLY DRY CONDITIONS FRIDAY FOR  
NORTHERN CALIFORNIA, ALTHOUGH A FEW LINGERING SHOWERS ACROSS THE  
CASCADES AND EXTREME NORTHERN SACRAMENTO VALLEY ARE POSSIBLE. THE  
NEXT LOW PRESSURE SYSTEM TO MAKE LANDFALL WILL AFFECT THE PACIFIC  
NORTHWEST AND THE CASCADE/COASTAL MOUNTAINS OF THE INTERIOR, WHICH  
WILL BRING ANOTHER ROUND OF PRECIPITATION CHANCES FOR SATURDAY.  
HIGH PRESSURE RETURNS FOR SUNDAY BEFORE THE NEXT WEATHER MAKING  
SYSTEM APPROACHES FOR EARLY NEXT WEEK, MAINLY AFFECTING THE  
NORTHERN VALLEY AND MOUNTAINS.  

 
   
AVIATION
 
 
RAIN CONTINUES TO MOVE ACROSS INTERIOR NORTHERN CALIFORNIA  
BRINGING REDUCTIONS IN CEILINGS AND VISIBILITY FOR  
FOOTHILL/MOUNTAIN AND VALLEY TERMINALS FOR THE SACRAMENTO AREA AND  
SOUTHWARD. PRECIPITATION WILL END LATER THIS MORNING AND  
CONDITIONS WILL IMPROVE BY AFTERNOON. ANOTHER ROUND OF CEILING AND  
VISIBILITY REDUCTIONS ARE EXPECTED TONIGHT.  

 
   
STO WATCHES/WARNINGS/ADVISORIES
 
 
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR WEST  
SLOPE NORTHERN SIERRA NEVADA-WESTERN PLUMAS COUNTY/LASSEN PARK.  
 

 
 

 
 
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