276  
FXUS66 KEKA 182333  
AFDEKA  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE EUREKA CA  
333 PM PST THU DEC 18 2014  
   
SYNOPSIS
 
AN APPROACHING COLD FRONT WILL BRING RAIN AND GUSTY  
WINDS TO NW CALIFORNIA LATE TONIGHT INTO EARLY MORNING HOURS ON  
FRIDAY. ADDITIONAL RAIN IS EXPECTED NORTH OF CAPE MENDOCINO FOR  
THE WEEKEND WITH A DRYING TREND EARLY NEXT WEEK.  
 

 
   
SHORT TERM
 
(TODAY THRU SUNDAY)LIGHT PRE-FRONTAL SHOWERS BEGAN TO  
IMPACT THE NORTH COAST LATE THIS MORNING. SHOWERS WILL SLOWLY  
INCREASE LATE THIS EVENING AHEAD OF THE MAIN FRONTAL BOUNDARY. THE  
HEAVIER AND MORE WIDESPREAD RAINFALL WILL NOT IMPACT NW CALIFORNIA  
UNTIL AFTER 10 PM TONIGHT AND PERSIST INTO THE EARLY MORNING HOURS  
FRIDAY. GUSTY WINDS WILL ACCOMPANY THE APPROACHING FRONT AND  
QUICKLY SUBSIDE AS IT PASSES. STORM TOTALS ARE STILL LOOKING TO  
AMOUNT TO 0.75-1.00 INCH OF RAIN WITH 1.5 INCHES ACROSS HIGHER  
TERRAIN. SNOW LEVELS WILL REMAIN ELEVATED TONIGHT THUS MOST OF THE  
SNOWFALL SHOULD BE RESTRICTED TO THE HIGHER PEAKS OF THE TRINITY  
ALPS.  
 
SHOWERS SHOULD DIMINISH BY LATE FRIDAY MORNING AS THE FRONTAL  
BOUNDARY PUSHES EASTWARD. AS THE UPPER LEVEL TROUGH SLIDES EAST THE  
FLOW BECOMES MORE ONSHORE AND ZONAL. THIS WILL SET UP FOR INCREASING  
WARM AIR AND MOISTURE ADVECTION TOWARD THE PACIFIC NORTHWEST. LIGHT  
SHOWERS WILL APPROACH THE NORTH COAST LATE FRIDAY EVENING THROUGH  
SATURDAY MORNING. THEN A PASSING WARM FRONT WILL BRING RAIN MOSTLY  
NORTH OF CAPE MENDOCINO THROUGH THE DAY SATURDAY AND DIMINISH INTO  
SUNDAY. MODELS HAVE BEEN CONSISTENT WITH RAINFALL TOTALS NEARING 2  
INCHES ACROSS DEL NORTE COUNTY SATURDAY. I STILL REMAIN A BIT  
SKEPTICAL WITH RAINFALL TOTALS AS MODELS TEND TO HAVE A DIFFICULT  
TIME NAILING WARM FRONTAL PRECIPITATION BUT ON THE OTHER HAND THERE  
WILL NO DOUBT BE RAIN IF ONLY ALONG THE OR/CA BORDER. THAT SAID I  
DIDN'T FEEL A NEED TO MAKE ANY DRASTIC CHANGES AND KEPT THE QPF  
CLOSE TO THE RFC FORECAST.  
   
LONG TERM
 
(MONDAY THRU THURSDAY) A LARGE BUILDING RIDGE OF HIGH  
PRESSURE WILL HELP DRY THE REGION OUT FOR THE EARLY HALF OF NEXT  
WEEK. ON WEDNESDAY AN INSIDE SLIDER SETS UP AND SLIDES DOWN THE  
PACIFIC NW CLIPPING THE NORTHERN AND NE PART OF THE EUREKA CWA. THE  
CONCERN WITH THIS IS THE POSSIBILITY OF A MUCH COLDER AIR MASS  
BRINGING SNOW TO LOWER ELEVATIONS LATE IN THE FORECAST, HOWEVER,  
THERE IS TOO MUCH UNCERTAINTY AT THIS TIME. LITTLE CHANGES WERE MADE  
IN THE LONG RANGE. \KML  
 

 
   
AVIATION
 
A COLD FRONT WILL MOVE ACROSS THE REGION TONIGHT  
PROVIDING PERIODS OF RAIN AS WELL AS LOWERING CIGS AND VSBYS.  
STRONG WINDS ALOFT WITH THE FRONTAL BOUNDARY MAY ALSO PRODUCE LOW  
LEVEL WIND SHEAR DURING FRONTAL PASSAGE. THE FRONT WILL EXIT TO  
THE SOUTHEAST FRIDAY MORNING AND CONDITIONS SHOULD GRADUALLY  
IMPROVE THROUGH THE DAY AS RAIN CHANGES TO ISOLATED OR SCATTERED  
SHOWERS.  
 

 
   
MARINE
 
A COLD FRONT WILL ADVANCE THROUGH THE WATERS THIS EVENING  
BRINGING A BRIEF PERIOD OF STRONG SOUTHERLY WINDS. GALE FORCE GUSTS  
ARE EXPECTED THIS EVENING IN THE OUTER WATERS NORTH OF CAPE  
MENDOCINO WHICH REQUIRED THE ISSUANCE OF A GALE WARNING. OTHERWISE  
WINDS WILL REMAIN AROUND 15 TO 25 KT. BEHIND THE FRONT A VERY LARGE  
SWELL IS FORECAST TO ARRIVE ON FRIDAY BUILDING TO BETWEEN 18 AND 20  
FEET AT 18 SECONDS BY FRIDAY NIGHT. THIS SWELL WILL BRING AN  
ENHANCED RISK OF SHOALING AND HAZARDOUS BAR CONDITIONS AT THE  
ENTRANCE TO HARBORS. A HAZARDOUS SEAS WATCH HAS BEEN ISSUED FOR  
WAVES AROUND 20 FEET. BREAKERS ARE EXPECTED TO BE BETWEEN 22 AND 25  
FEET AS THE SWELL HITS THE COASTLINE LATE FRIDAY AFTERNOON THROUGH  
SATURDAY. A HIGH SURF ADVISORY HAS BEEN ISSUED. THERE STILL HAS NOT  
BEEN A GOOD JASON-2 PASS THROUGH THE CORE OF THE WAVES NEAR THE LOW  
IN THE PACIFIC SOUTH OF ALASKA TO CONFIRM THE SWELL MAGNITUDE BUT  
WESTERLY WINDS OF 40 TO 50 KT HAVE OCCURRED FOR 24-36 HOURS WITH THE  
STORM AND THE SWELL MAGNITUDE FROM THE ENP GUIDANCE LOOKS TO BE ON  
TARGET. WE WILL HAVE INDISPUTABLE CONFIRMATION ONCE THE SWELL GOES  
BY BUOY #2 FRIDAY MORNING...UNTIL THEN THE SWELL FORECAST HAS BEEN  
BASED ON THE WAVE MODEL OUTPUT. WE DID RAMP UP THE SWELL HEIGHTS ON  
SATURDAY BY 1-2 FT ABOVE THE MODEL OUTPUT. IT WILL STILL BE  
HAZARDOUS TO VENTURE OUT TO THE BEACHES THROUGH THE DAY ON SATURDAY.  
THUS THE ADVISORY RUNS THROUGH THE AFTERNOON HOURS ON SATURDAY.  
 
A WARM FRONT WILL BRING A PERIOD OF SMALL CRAFT OR NEAR GALE  
SOUTHERLY WINDS SATURDAY WITH THE STRONGEST WINDS IN THE NORTHERN  
WATERS. BEHIND THE FRONT HIGH PRESSURE WILL SLOWLY BUILD OVER THE  
AREA SUN THROUGH TUE ALLOWING WINDS TO BECOME LIGHTER AND NORTHERLY.  
THE MODELS DO SHOW A COLD FRONTAL SYSTEM DIVING DOWN FROM THE NW  
AROUND MID WEEK WHICH MAY GENERATE A BLAST OF N AND NW WINDS AS WELL  
AS LARGE STEEP SEAS. IF THIS SYSTEM DEVELOPS FARTHER TO  
THE EAST...THEN WINDS WILL BE MOSTLY LIGHT EASTERLY.  
 

 
   
COASTAL FLOODING
 
PROLONGED SOUTHERLY WINDS IN CONJUNCTION WITH  
HIGH ASTRONOMICAL TIDES WILL BRING THE POTENTIAL FOR MINOR COASTAL  
FLOODING OVER THE WEEKEND. TIDES HAVE BEEN RUNNING 1 TO 2 FT ABOVE  
PREDICTED LEVELS. IF THESE DIFFERENCES REMAIN CONSTANT OVER THE  
NEXT FEW DAYS THEN MINOR COASTAL FLOODING WILL BE LIKELY AROUND  
LOW LYING AREAS OF HUMBOLDT BAY. ADDITIONALLY, LARGE SURF ON  
FRIDAY AND SATURDAY WILL CAUSE WAVES TO PUSH FARTHER UP BEACHES  
AND POTENTIALLY IMPACT AREAS THAT TYPICALLY REMAIN DRY. FRIDAY  
MORNING MAY BE THE FIRST DAY OF MINOR FLOODING IF THE ANOMALY  
REMAINS GREATER THAN 1 FOOT. WE WILL CONTINUE TO MONITOR THE TIDE  
LEVELS BEFORE ISSUING ANY ADVISORIES. \KML  
 

 
   
EKA WATCHES/WARNINGS/ADVISORIES
 
 
CA...  
HIGH SURF ADVISORY FROM 2 PM FRIDAY TO 6 PM PST SATURDAY FOR  
CAZ001-002.  
 
NORTHWEST CALIFORNIA COASTAL WATERS...  
SMALL CRAFT ADVISORY UNTIL 2 PM PST FRIDAY FOR PZZ450-455.  
 
HAZARDOUS SEAS WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY  
AFTERNOON FOR PZZ450-455.  
 
HAZARDOUS SEAS WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY  
AFTERNOON FOR PZZ470-475.  
 
GALE WARNING UNTIL 11 PM PST THIS EVENING FOR PZZ470.  
 
SMALL CRAFT ADVISORY UNTIL NOON PST FRIDAY FOR PZZ475.  

 
 

 
 
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