059  
FXUS66 KEKA 092217  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
317 PM PDT THU APR 9 2020  
   
SYNOPSIS
 
DRY WEATHER IS EXPECTED TO PREVAIL THROUGH MOST OF  
NEXT WEEK AS AN UPPER RIDGE DOMINATES. TEMPERATURES WILL  
GENERALLY REMAIN ABOVE NORMAL IN THE INTERIOR. PERSISTENT MARINE  
AIR WILL BRING PERIODS OF LOW CLOUDINESS AND ONSHORE WINDS,  
KEEPING COASTAL AREAS COOLER.  
 

 
   
DISCUSSION
 
WITH AN INVERTED SURFACE TROUGH SHIFTING JUST  
OFFSHORE LAST NIGHT, DEEPENING MARINE LAYER CLOUDINESS FLOWED  
QUICKLY NORTHWARD TO CRESCENT CITY BY MID-MORNING TODAY. WITH  
THAT, ANY HOPES OF ANOTHER SUNNY AND MILD AFTERNOON WERE DASHED  
FOR MOST OF OUR COASTAL LOCATIONS. THE LONE EXCEPTIONS ARE A FEW  
SPOTS TO THE NORTH OF COASTAL HEADLANDS AND MOUNTAINOUS TERRAIN,  
SUCH AS FORTUNA AND FERNDALE. MEANWHILE, WITH A VERY DEEP MARINE  
LAYER INTRUSION ACROSS MENDOCINO COUNTY, CLOUDINESS HAS BEEN SLOW  
TO BREAK OR SCATTER EVEN AROUND UKIAH, WHERE TEMPERATURES HAVE  
STRUGGLED TO GET INTO THE 60S. PORTIONS OF THE KLAMATH, TRINITY,  
AND UPPER MAD RIVER VALLEYS THAT WERE PROTECTED FROM THE SOUTHERLY  
FLOW OF MARINE AIR HAVE MANAGED TO RISE INTO THE 70S ONCE AGAIN  
THIS AFTERNOON.  
 
HEADING INTO TONIGHT, WE'LL LOOK FOR MARINE CLOUDINESS TO THICKEN  
AND EXPAND ONCE AGAIN IN THOSE AREAS WHERE COOLER MARINE AIR  
INTRUDED LAST NIGHT AND TODAY. THE REST OF THE INTERIOR INCLUDING  
MOST OF TRINITY COUNTY WILL REMAIN CLEAR. EXPECT THE MARINE LAYER  
CLOUDINESS TO BE QUITE DEEP; FROM 2000 TO 3000 FEET FOR HUMBOLDT  
AND DEL NORTE, BUT EVEN UP TO 4000 FEET ACROSS MENDOCINO AND LAKE  
COUNTIES. COMBINED WITH MID AND UPPER-LEVEL RIDGING ALOFT, CLOUDS  
WILL BE SLOW TO ERODE BACK TOWARD THE COAST ON FRIDAY. AS SURFACE  
WINDS SHIFT TOWARD THE NORTHWEST AND ONSHORE FOR THE AFTERNOON,  
WE ARE THINKING THAT ONLY LIMITED BREAKS OF SUN WILL BE FOUND  
ALONG THE COASTAL PLAIN, OUTSIDE OF THE LOST COAST AREA ADJACENT  
TO THE KING RANGE AROUND SHELTER COVE. THAT SAID, MOST INTERIOR  
VALLEYS INCLUDING THOSE ACROSS MENDOCINO AND LAKE COUNTIES SHOULD  
SEE A FAIR AMOUNT OF SUN TOMORROW AND TEMPS INTO THE 60S, WITH  
EVEN LOW TO MID 70S ALONG THE TRINITY RIVER.  
 
THIS WEEKEND SHOULD BRING A SHALLOWER MARINE LAYER, WITH STRONGER  
NORTHWEST WINDS PUSHING ONSHORE AND INLAND DURING THE AFTERNOONS  
AND EVENINGS, WHICH SHOULD PROMOTE MORE WIDESPREAD AFTERNOON  
CLEARING OF THE MARINE STRATUS AND FOG. OTHERWISE, STRONG UPPER-  
LEVEL HIGH PRESSURE LOCKED IN PLACE ACROSS THE EASTERN PACIFIC  
WILL EFFECTIVELY BLOCK PACIFIC MOISTURE AND ANY STORM SYSTEMS FROM  
THREATENING OUR AREA THROUGH NEXT WEEK. SOME UPPER- LEVEL TROUGHS  
ROUNDING THE TOP OF THE RIDGE AND DIVING ACROSS THE NORTHERN  
ROCKIES COULD POSSIBLY CLIP OUR AREA AT TIMES OVER THE NEXT 7  
DAYS. IT IS NOT OUTSIDE OF THE REALM OF POSSIBILITY THAT ONE OF  
THESE MAY TRIGGER A COUPLE STRAY INTERIOR MOUNTAIN SHOWERS,  
PERHAPS SPECIFICALLY ON SUNDAY AFTERNOON, BUT AT THIS POINT THE  
CHANCE LOOKS LOW ENOUGH TO LEAVE OUT OF THE FORECAST. WITH THAT,  
EXPECT DRY CONDITIONS, WITH SEASONABLE COASTAL TEMPERATURES AND  
INLAND TEMPERATURES MAINLY STAYING WELL ABOVE SEASONAL AVERAGES  
FOR THE WEEKEND INTO NEXT WEEK. /AAD  
 

 
   
AVIATION
 
A RATHER COMPLEX CLOUD PATTERN EXISTS ACROSS THE AREA  
THIS AFTERNOON. SOUTHERLY CLOUD-LEVEL FLOW CONTINUES TO PUSH LOW-  
LEVEL MOISTURE AND STRATUS INTO THE COAST FROM CAPE MENDOCINO  
NORTHWARD. THERE ARE SOME BREAKS IN THIS CLOUDINESS ALONG PORTIONS  
OF THE IMMEDIATE COAST, BUT MOISTURE CONTINUES TO PILE UP ON THE  
WINDWARD SIDE OF THE COASTAL TERRAIN. PER COASTAL PROFILER DATA, THE  
MARINE LAYER APPEARS TO BE ABOUT 3500 FEET DEEP AT ACV AND 5000 FEET  
DEEP S OF THE AREA AT BODEGA BAY. MODELS INDICATE THAT THE MARINE  
LAYER WILL CONTINUE TO DEEPEN ALONG THE REDWOOD COAST TO 5000 FEET  
LATER TONIGHT AND ON FRIDAY BEFORE DROPPING BACK CLOSER TO 3000 FEET  
ON SATURDAY. EXPECT CLOUDS TO LOWER AT BOTH KACV AND KCEC THROUGH  
THE EVENING HOURS WITH THE CHANCE OF VISIBILITY REDUCTIONS LATER IN  
THE FORECAST PERIOD. CEILINGS MAY ONCE AGAIN HOLD IN FOR THE DAY ON  
FRIDAY WITH SLOWLY RISING CEILING HEIGHTS. WINDS WILL BE GENERALLY  
LIGHT, WITH SOME GUSTS TO AROUND 15 KT AT KCEC INTO THE EVENING  
HOURS.  
 
AT KUKI, CEILINGS HAVE RISEN TO OVER 4000 FT, BUT SKIES REMAIN  
BROKEN TO OVERCAST. EXPECT CEILINGS TO DROP BACK TO MVFR LEVELS  
LATER TONIGHT. NO SIGNIFICANT VISIBILITY REDUCTIONS ARE  
ANTICIPATED AT THIS TIME. SOUTHERLY WINDS WILL GUST TO 15 TO 20 KT  
THROUGH THE EARLY EVENING HOURS. /SEC  
 

 
   
MARINE
 
THE INTERIOR THERMAL TROUGH HAS PUSHED W A LITTLE CLOSER  
TO THE COAST TODAY AND DISRUPTED THE SURFACE PRESSURE GRADIENT. THIS  
HAS INDUCED A BRIEF WEAKENING TREND IN THE PERSISTENT NORTHERLY  
WIND REGIME WHICH HAS DOMINATED THE PAST SEVERAL DAYS. A SMALL CRAFT  
ADVISORY CONTINUES ACROSS THE OUTER WATERS. THE S ADVISORY WILL END  
AT 6 PM, WHILE THE N ADVISORY IS EXPECTED TO EXPIRE FRIDAY MORNING.  
THE LULL IN THE NORTHERLIES WILL BE SHORT-LIVED AS THE COASTAL  
GRADIENT TIGHTENS AGAIN AND NORTHERLIES RE-INTENSIFY FROM LATE  
FRIDAY AFTERNOON INTO THE WEEKEND. /CB&SEC  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL  
NOON PDT FRIDAY FOR PZZ470.  
 
SMALL CRAFT ADVISORY UNTIL 6 PM PDT THIS EVENING FOR PZZ475.  
 

 
 

 
 
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