Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 191224
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
424 AM PST FRI DEC 19 2014

.SYNOPSIS...A COLD FRONT AND ASSOCIATED MODERATE TO HEAVY RAIN IS
CURRENTLY MOVING ACROSS THE AREA THIS MORNING. SHOWERS BEHIND IT
WILL PERSIST THROUGH THE EVENING. LATE TONIGHT INTO THE WEEKEND A
WARM FRONT WILL BRING ADDITIONAL RAIN. LOOK FOR A DRYING TREND
EARLY NEXT WEEK.

&&

.DISCUSSION...THE COLD FRONT IS CURRENTLY MOVING ACROSS THE AREA.
AS OF 230 AM THE BACK EDGE OF THE RAIN HAS MOVED THROUGH EUREKA.
RAINFALL AMOUNTS HAVE BEEN NEAR OR SLIGHTLY HIGHER THAN EXPECTED
RANGING FROM 0.75 TO OVER 2 INCHES. SNOW LEVELS WITH MOST OF THE
PRECIP HAVE BEEN OVER 6000 FEET. RADAR CONTINUES TO SHOW SHOWERS
OVER THE COASTAL WATERS BEHIND THE FRONT. SNOW LEVELS BEHIND THE
FRONT WILL DROP MODESTLY TO AROUND 5000 FEET AND SNOW AMOUNTS WILL
BE 1 TO 2 INCHES BEHIND THE FRONT. THE FRONT WILL CONTINUE TO
PUSH EASTWARD THIS MORNING...FINALLY MOVING OUT OF THE AREA BY MID
MORNING. SHOWERS WILL VARY IN INTENSITY AND COVERAGE BEHIND THE
FRONT THIS AFTERNOON AS SEVERAL IMPULSES MOVING THROUGH THE FLOW
ENHANCE IT.

LATE TONIGHT WARM ADVECTION RAIN IS EXPECTED TO START AS THE
HEIGHTS BEGIN TO BUILD OVER THE AREA. THE WARM FRONTAL RAIN IS
EXPECTED TO DEVELOP OVER AREAS NORTH OF CAPE MENDOCINO INITIALLY
AND SPREAD SOUTH THROUGH THE DAY. THIS IS SLIGHTLY FASTER AND
FARTHER SOUTH THAN PREVIOUS MODEL RUNS HAVE BEEN SHOWING SO
TRENDED THE QPF AMOUNTS TOWARDS THE NEW MODELS...SLIGHTLY UP FROM
WHAT THE RFC HAD EARLY IN THE EVENT. NAEFS ENSEMBLES SHOW
INTEGRATED WATER VAPOR TRANSPORT OF 2 TO 3 STANDARD DEVIATIONS
ABOVE NORMAL REMAINS AIMED AT DEL NORTE COUNTY FOR 18 HOURS. THIS
INCREASES CONFIDENCE IN THE RAINFALL AMOUNTS. THIS RAIN WILL
REMAIN IN PLACE SATURDAY BEFORE STARTING TO DIMINISH AND MOVE BACK
NORTH ON SATURDAY NIGHT AND SUNDAY. CURRENTLY THERE IS NO FLOODING
FORECAST FOR ANY RIVERS...HOWEVER A SLIGHT SHIFT IN INTENSITY OR
DURATION COULD BRING SOME MINOR FLOODING TO THE SMITH RIVER.
RAINFALL AMOUNTS LOOK TO RANGE FROM 0.5 INCHES IN THE SOUTH TO
NEARLY 4 INCHES IN THE NORTH. SNOW LEVELS WILL RISE QUICKLY AS THE
PRECIP BEGINS TO MOVE INTO THE AREA. THERE IS STILL THE CHANCE
THAT SOME COLD AIR MAY BE TRAPPED IN THE EASTERN VALLEYS OF
TRINITY COUNTY...BUT IT IS STARTING TO LOOK LIKE THE AIRMASS WILL
NOT BE VERY COLD TO START OUT...THEREFOR THERE WILL BE NO COLD
AIR TO TRAP.

MONDAY THE HEIGHTS CONTINUE TO BUILD WITH MUCH OF THE AREA
SEEING DRY WEATHER WITH SOME SUNSHINE POSSIBLE. SOME LIGHT RAIN
OR DRIZZLE MAY CONTINUE IN DEL NORTE COUNTY AND CLOUDS WILL LIKELY
BE SLOW TO CLEAR OUT. MONDAY NIGHT INTO TUESDAY WILL LIKELY SEE
WIDESPREAD FOG IN THE INLAND...ALTHOUGH WEAK NORTHERLY FLOW MAY
KEEP THE COAST PARTLY CLOUDY. TUESDAY NIGHT THERE MAY BE SOME
ADDITIONAL FOG IN THE INLAND AREAS.

WEDNESDAY THE GFS AND ECMWF HAVE COME INTO BETTER AGREEMENT ON THE
NEXT SYSTEM. CURRENT RUNS BOTH HAVE IT AS MORE OF AN OPEN WAVE
MOVING DOWN FROM THE GULF OF ALASKA. THIS BRINGS BOTH MORE
MOISTURE AND WARMER AIR. INCREASED POPS ON WEDNESDAY TO ACCOUNT
FOR THIS...BUT CONFIDENCE IS STILL LOW AS A SLIGHT SHIFT IN THE
TRAJECTORY COULD RESULT IN A BIG DIFFERENCE TO THE WEATHER.
CURRENT MODELS BRING ACCUMULATING SNOW TO AROUND 3000 FEET
WEDNESDAY AFTERNOON. CONFIDENCE IS LOW ON THIS AND THIS WILL NEED
TO BE MONITORED.

THURSDAY STILL LOOKS LIKE A CHILLY MORNING...ALTHOUGH THERE ARE
SOME QUESTIONS ON CLOUD COVER. FRIDAY THE CHILLY AIRMASS REMAINS
IN PLACE. THERE IS SLIGHT CHANCE FOR RAIN OR SNOW THESE DAYS WITH
A FEW WAVES MOVING DOWN THROUGH THE NORTHWESTERLY FLOW...BUT
AMOUNTS LOOK TO BE QUITE LIGHT. MKK

&&

.AVIATION...MORNING RADAR SHOWS SHOWERS ACROSS MOST OF NORTHWEST
CALIFORNIA. EXPECT MOSTLY VFR TO PREVAIL WITH SHORT PERIODS OF MVFR
IN HEAVIER SHOWERS THIS MORNING.

&&

.MARINE...THE MORNING BUOY OBSERVATIONS SHOW A FRESH BREEZE WITH
HIGHER GUSTS. WAVE HEIGHTS RANGE FROM 9-10 FT WITH MIXED SEAS, SHORT
PERIOD WIND-DRIVEN WAVES FROM THE SOUTH AND LONGER PERIOD SWELL
BUILDING IN FROM THE WEST. THE ASCAT PASS JUST MISSED OUR WATERS
THIS MORNING. A FRONT IS CURRENTLY MOVING INLAND AND IN IT`S WAKE
WILL BE EASING WINDS FOR TODAY. HOWEVER, A DISTANT STORM HAS
GENERATED A VERY LARGE LONG PERIOD WESTERLY SWELL. OFFSHORE BUOY #2
STARTED REPORTING THIS SWELL AT 2 AM WITH A HEIGHT OF 17 FT AT 19
SECONDS. SWELL DECAY CALCULATIONS PUT THIS INITIALLY AROUND 15 FT
NEAR 20 SECONDS, ARRIVING EARLY THIS AFTERNOON. THIS WOULD EQUATE TO
BREAKERS APPROACHING 25 FT. WITH ONLY ONE HOUR OF OBSERVATIONS FROM
BUOY #2 AND THIS FORECAST DEADLINE AND THE EXPECTATION THAT THE NEXT
FEW HOURS WILL SEE HIGHER HEIGHTS REPORTED FROM THIS BUOY, UPGRADED
THE SE.A (HAZ SEAS WATCH) TO A SE.W (HAZ SEAS WARNING) AND LEFT
THE SU.Y UNCHANGED. EXPECT THIS LONG PERIOD WESTERLY SWELL TO
RAPIDLY BUILD THIS AFTERNOON AND TONIGHT WHILE REMNANT SHORT-
PERIOD WAVES FROM THE SOUTH CONTINUE. MODELS ARE IN GOOD AGREEMENT
SHOWING A WARM FRONT BRINGING INCREASED SOUTHERLY WINDS AND SHORT-
PERIOD WIND- DRIVEN SOUTHERLY WAVES TO THE WATERS ON SATURDAY.
EXPECT THE WORST CONDITIONS TO BE ACROSS THE OUTER WATERS,
ESPECIALLY ZONE 470. ISSUED A SC.Y (SMALL CRAFT ADVISORY) FOR
THIS ZONE TO ACCOUNT FOR THE WINDS, BUT WOULDN`T BE SURPRISED TO
SEE THIS EXPANDED TO OTHER ZONES WITH THE AFTERNOON PACKAGE. SOME
GUSTS TO GALE FORCE ARE EXPECTED ON SATURDAY IN ZONE 470 ALONG
WITH SHORT- PERIOD SOUTHERLY WAVES APPROACHING 10 FT. BUT DON`T
FEEL WINDS WILL BE STRONG ENOUGH OVER A LARGE ENOUGH AREA TO ISSUE
A GL.A (GALE WATCH) WITH THIS PACKAGE. CONDITIONS SHOULD IMPROVE
EARLY NEXT WEEK AS HIGH PRESSURE BEGINS TO BUILD OVER THE REGION.
WENT WITH THE CONSMODEL FOR THE WINDS AND LOADED THE NWPS.

&&

.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 0.5 TO 1.5 FT
ABOVE PREDICTED LEVELS...WITH THE HIGHEST ANOMALIES AT THE NORTH
SPIT IN HUMBOLDT BAY. AT THE PREVIOUS HIGH TIDE THE NORTH SPIT WAS
1.24 FT ABOVE ASTRONOMICAL. IF THIS PERSISTS AS EXPECTED IT WILL
PEAK AT 8.83 FT. AT THIS HEIGHT MINOR FLOODING STARTS TO OCCUR IN
LOW LYING AREAS AROUND HUMBOLDT BAY INCLUDING KING SALMON AND
JACKSON RANCH ROAD IN THE ARCATA BOTTOMS. SO HAVE ISSUED A
COASTAL FLOOD ADVISORY.

IF THESE DIFFERENCES REMAIN CONSTANT....AS EXPECTED...OVER THE
NEXT FEW DAYS THEN MINOR COASTAL FLOODING WILL BE LIKELY CONTINUE
AND ADDITIONAL ADVISORIES MAY BE NEEDED AS THE ASTRONOMICAL TIDES
INCREASE.

ADDITIONALLY, LARGE SURF ON SATURDAY WILL CAUSE WAVES TO PUSH
FARTHER UP BEACHES AND POTENTIALLY IMPACT AREAS THAT TYPICALLY
REMAIN ALONG THE ENTIRE COAST. MKK

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     HIGH SURF ADVISORY FROM 2 PM THIS AFTERNOON TO 6 PM PST SATURDAY
     FOR CAZ001-002.

     COASTAL FLOOD ADVISORY FROM 8 AM TO 10 AM PST THIS MORNING
     FOR CAZ001.

NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 2 PM PST THIS AFTERNOON
     FOR PZZ450-455.

     HAZARDOUS SEAS WARNING FROM 2 PM PST THIS AFTERNOON THROUGH
     SATURDAY AFTERNOON FOR PZZ450-455.

     SMALL CRAFT ADVISORY UNTIL NOON PST TODAY FOR PZZ470-475.

     SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 3 AM PST SUNDAY
     FOR PZZ470.

     HAZARDOUS SEAS WARNING FROM NOON PST TODAY THROUGH SATURDAY
     AFTERNOON FOR PZZ470-475.

&&

$$

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