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394
FXUS66 KEKA 190349
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
749 PM PST THU DEC 18 2014

.SYNOPSIS...A COLD FRONT WILL BRING RAIN AND GUSTY WINDS TO NW
CALIFORNIA 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.

&&

.UPDATE...EVENING RADAR INDICATES RAIN FILLING IN QUICKLY OFF THE
COAST AS THE COLD FRONT APPROACHES. SO HAVE UPDATED THE FORECAST
TO INCREASE POPS THROUGH 10 PM. AFTER 10 PM POPS WERE ALREADY NEAR
100 PERCENT, SO NO INCREASE WAS NEEDED OR POSSIBLE. MAY NEED TO
UPDATE WINDS AS THE FRONT HITS THE COAST AND WE GET AN IDEA OF HOW
STRONG THE WINDS ACTUALLY BECOME. OTHERWISE, THE FORECAST SEEMS TO
BE ON TRACK FOR THE OVERNIGHT PERIOD. BFG

&&

.PREV DISCUSSION......ISSUED AT 333 PM PST...

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...
     HIGH SURF ADVISORY FROM 2 PM FRIDAY TO 6 PM PST SATURDAY FOR
     PZZ410-450-455.

     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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