909  
FXUS66 KEKA 291000  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
300 AM PDT MON MAY 29 2017  
   
SYNOPSIS
 
COASTAL AREAS WILL CONTINUE TO BE UNDER THE INFLUENCE  
OF A STUBBORN MARINE LAYER WITH COOL CLOUDY CONDITIONS. INTERIOR  
AREAS MAY SEE ISOLATED THUNDERSTORMS DEVELOP OVER THE MOUNTAINS  
MONDAY AFTERNOON...FOLLOWED BY COOLER AND SHOWERY CONDITIONS FOR  
THE REMAINDER OF THE WEEK.  
 

 
   
DISCUSSION
 
A TRANSITION OF AIRMASSES WILL BEGIN TODAY  
AS THE UPPER RIDGE OF HIGH PRESSURE AXIS MOVES EAST OF  
CA AND ALLOWS AN UPPER LEVEL TROUGH TO APPROACH THE COAST.  
THE CURRENT STUBBORN MARINE LAYER SHOULD PERSIST AT LEAST ONE  
MORE DAY THUS ANOTHER GLOOMY DAY IS EXPECTED FOR MOST OF THE  
COASTAL AREAS...BUT SOME MIXING MAY FINALLY OCCUR ON TUESDAY. FOR  
INTERIOR AREAS HOWEVER THE APPROACHING TROUGH ALOFT WILL PROVIDE  
A COMBINATION OF INCREASED LOW- LEVEL MOISTURE AND INSTABILITY,  
ALONG WITH SOME WEAK DYNAMIC FORCING ALOFT. THIS WILL LEAD TO  
INCREASED POTENTIAL OF CONVECTION OVER THE INTERIOR THIS  
AFTERNOON. ISOLATED THUNDERSTORMS ARE POSSIBLE, MAINLY OVER  
TRINITY COUNTY BUT GIVEN THE SOUTHEASTERN STEERING FLOW...ANY  
STORMS THAT DEVELOP MAY FLOAT WESTWARD INTO EASTERN HUMBOLDT OR  
DEL NORTE COUNTIES AS WELL. EVEN BETTER CHANCES OF SHOWERS ARE  
EXPECTED ON TUESDAY, BUT, AS MENTIONED BY PREVIOUS SHIFTS,  
INSTABILITY WILL BE WANING DURING THIS TIME FRAME AS COOLER AIR  
MOVES INTO THE AREA. FOR NOW, HAVE CONTINUED WITH JUST A SHOWERY  
FORECAST FOR TUESDAY. A COUPLE OF WEAK SURFACE FRONTS WILL  
APPROACH THE OR COAST THROUGH MID- WEEK, BUT THESE WILL MAINLY  
SERVE TO INCREASE CLOUDINESS ACROSS PARTS OF OUR COUNTY WARNING  
AREA. HEIGHTS ARE EXPECTED TO BUILD OVER THE W COAST BY LATE IN  
THE COMING WEEK, WITH DECREASING CHANCES OF RAIN AND WARMER  
TEMPERATURES. MAXIMUM TEMPERATURES MAY ONCE AGAIN RISE INTO THE  
90S OVER PORTIONS OF THE INTERIOR BY NEXT WEEKEND.  
 

 
   
AVIATION
 
THE MARINE LAYER WILL CONTINUE TO SHRINK IN DEPTH  
TODAY AS THE UPPER LEVEL SYSTEM OFFSHORE MOVES ACROSS THE AREA.  
GREATEST CHANGE IN THE LAST 24 HOURS WILL COME TONIGHT WHEN THE BACK  
EDGE OF THIS SYSTEM PASSES OVER THE COAST. EXPECT COASTAL SITES  
WILL SEE IFR AND MVFR CIGS THIS MORNING WITH CIGS RISING THOUGH THE  
DAY AS THE UPPER SYSTEM APPROACHES. AT TIMES PATCHY DRIZZLE OVER THE  
COAST THIS MORNING WILL REDUCE VISIBILITY AT THESE SITES. EXPECT VFR  
CONDITIONS TO CONTINUE FOR INLAND AREAS.  
 

 
   
MARINE
 
NORTH-NORTHWEST WINDS FOR THE MOST PART RETURNED TO THE  
COASTAL WATERS TODAY. NORTHERLY WINDS WILL BE BORDERLINE FOR AN  
ADVISORY IN THE WATERS SOUTH OF CAPE MENDOCINO TODAY THROUGH LATE  
TONIGHT. HIGH RESOLUTION MODELS INDICATE A WEAK EXPANSION FAN  
DEVELOPING DOWNWIND OF CAPE MENDOCINO BY MONDAY MORNING. STEEP SHORT  
PERIOD NORTHERLY WIND WAVES ARE EXPECTED TO BUILD TO 5 TO 7 FT ON  
MONDAY AS WINDS REACH 20 TO 25 KT. THEREFORE, A SMALL CRAFT ADVISORY  
HAS BEEN HOISTED FOR THE OFFSHORE WATERS SOUTH OF CAPE MENDO.  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY FOR PZZ475.  
 

 
 

 
 
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