Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 281220
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
420 AM PST SAT FEB 28 2015

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL CONTINUE TO BRING SHOWERS
AND A SLIGHT CHANCE FOR THUNDERSTORMS TO THE AREA TODAY. HIGH
PRESSURE WILL BRING DRY WEATHER FOR SUNDAY WITH ANOTHER CHANCE
FOR LIGHT RAIN MONDAY. HIGH PRESSURE RETURNS TUESDAY AND PERSISTS
THROUGH MUCH OF THE WEEK.

&&

.DISCUSSION...WATER VAPOR SAT SHOWS THE UPPER LEVEL TROUGH SINKING
SOUTH OVER THE AREA. AS OF 3AM RADAR SHOWS NUMEROUS SHOWERS JUST
OFF THE COAST AND A FEW ARE MOVING ONTO THE NEAR COASTAL AREAS.
THIS LOOKS TO PERSIST THROUGH MORNING HOURS. THIS AFTERNOON AS THE
HEATING OF THE DAY PICKS UP THERE WILL LIKELY BE SOME SHOWERS OVER
THE INLAND AREAS...WITH THE COAST BEING MAINLY DRY...ESPECIALLY
NORTH OF CAPE MENDOCINO. THERE IS ALSO A SLIGHT CHANCE FOR SOME
THUNDERSTORMS THIS AFTERNOON. THE BEST INSTABILITY LOOKS TO BE
SOUTH OF CAPE MENDOCINO...SO HAVE TRIMMED BACK THE NORTHERN EXTENT
OF THE SLIGHT CHANCE OF THUNDERSTORMS.

TONIGHT AS THE TROUGH PUSHES SOUTH HIGH PRESSURE BUILDS INTO THE
AREA. CLEARING SKIES AND A COOL AIRMASS WILL ALLOW TEMPERATURES TO
DROP NICELY ACROSS THE AREA. WITH THE START OF THE GROWING SEASON
ALONG THE COAST AND IN MENDOCINO COUNTY WENT AHEAD AND ISSUED A
FROST ADVISORY. ALTHOUGH HIGHER ELEVATIONS MAY SEE SOME WIND THE
VALLEYS AND COASTAL AREAS WILL LIKELY SEE SOME AREAS OF FROST.
SUNDAY LOOKS TO BE DRY AND SUNNY WITH OFFSHORE FLOW.

THE NEXT SYSTEM MOVING INTO THE AREA HAS SPED UP SLIGHTLY. THE
BEST CHANCE FOR RAIN LOOKS TO BE MONDAY MORNING ALONG THE REDWOOD
COAST. AREAS SOUTH AND EAST WILL LIKELY SEE VERY LITTLE RAIN.
CLOUDS WILL QUICKLY INCREASE SUNDAY NIGHT...AND THIS SHOULD KEEP
FROST FROM FORMING AND TEMPERATURES UP. MONDAY AFTERNOON SKIES
SHOULD START TO CLEAR...ALTHOUGH THERE MAY BE A FEW ISOLATED
SHOWERS AROUND.

TUESDAY THROUGH THURSDAY HIGH PRESSURE LOOKS TO BUILD IN ACROSS
THE AREA BRINGING SUNNY SKIES AND DRY CONDITIONS. NIGHTS WILL BE
CHILLY WITH SOME VALLEY FOG POSSIBLE IN THE NORTH. DAYTIME
TEMPERATURES WILL BE UNSEASONABLY WARM ONCE AGAIN. LATE IN THE
WEEK THERE IS THE POSSIBILITY OF ANOTHER SYSTEM BRINGING SOME
LIGHT RAIN TO THE AREA...ALTHOUGH THEY TEND TO BE SLOWING DOWN.
THIS WILL NEED TO BE WATCHED. MKK

&&

.AVIATION...REGION WIDE AIRPORTS HAVE BEEN OBSERVING IMPROVED FLYING
CONDITIONS EARLY THIS MORNING WITH ONLY LINGERING SHOWERS BRINGING
PERIODIC MVFR CEILINGS. COLDER AND DRIER AIR ASSOCIATED WITH THE
UPPER TROUGH OVER THE PACIFIC NORTHWEST WILL MEAN MOSTLY VFR
CONDITIONS ACROSS NORTHWESTERN CALIFORNIA TODAY. HOWEVER, AN
EMBEDDED SHORTWAVE WILL PROLONG SHOWER ACTIVITY THIS AFTERNOON WITH
THE POTENTIAL FOR THUNDERSTORMS LASTING INTO THE EVENING. I
REFRAINED FROM ADDING TS INTO THE TAFS AS IT LOOKS LIKE IT ONLY BE A
SLIGHT CHANCE FOR DEVELOPMENT FOR MOSTLY AREAS SOUTH OF CAPE
MENDOCINO. OTHERWISE EXPECT PERIODIC MVFR WITH LINGERING SHOWERS
TODAY. KML

&&

.MARINE...NORTHERLY WINDS WILL INCREASE AND STEEP SEAS WILL BUILD
TODAY AS A POTENT LOW PRESSURE SYSTEM TIGHTENS THE PRESSURE GRADIENT
AS IT DIVES SOUTHWARD. THE WORST CONDITIONS WILL BE FARTHER OFFSHORE
WITH GALE FORCE WIND GUSTS IN THE NORTHERN ZONE AND SEAS NEARING 10
TO 14 FT BY THIS EVENING. A HAZARDOUS SEAS WARNING HAS BEEN ISSUED
FOR MARINE ZONES 450 AND 475 STARTING THIS AFTERNOON AS LARGE STEEP
SEAS ARE EXPECTED TO PROPAGATE INTO THESE ZONES. CONDITIONS WILL
EASE SLIGHTLY ON SUNDAY AS THE LOW PRESSURE SYSTEM WEAKENS, HOWEVER,
ANOTHER SYSTEM WILL IMPACT THE REGION EARLY NEXT WEEK CAUSING
INCREASING WINDS AND BUILDING SEAS THROUGH TUESDAY. THE SMALL CRAFT
ADVISORY FOR THE SOUTHERN OUTER WATERS WAS EXTENDED THROUGH TUESDAY
NIGHT AS BOTH WINDS AND SEAS ARE EXPECTED TO MEET CRITERIA AND
POSSIBLY EXCEED GALE CRITERIA. ADDITIONAL PRODUCTS WILL LIKELY BE
NEEDED FOR THE OTHER ZONES THROUGH EARLY NEXT WEEK BUT WILL WAIT FOR
THE EXPIRATION OF THE EXISTING WARNINGS BEFORE ISSUING ANY NEW
PRODUCTS.

A MORE SUSTAINED LULL WILL COME LATE THIS UPCOMING WEEK AS
A RIDGE OF HIGH PRESSURE SETTLES OVER THE WESTERN UNITED STATES
ALLOWING THE PRESSURE GRADIENT TO RELAX. ON A DIFFERENT NOTE, WAVE
MODELS HAVE BEEN A PREDICTING A SOUTHERLY SWELL TO IMPACT THE
CALIFORNIA COAST ON TUESDAY AND BUILD THROUGH THE WEEK. SOUTHERN
HEMISPHERE MODEL DATA SHOWS A POTENT LOW JUST SW OF CHILE... WHICH IS
LIKELY GENERATING THE SWELL. THERE ARE SOME INITIAL CONCERNS WITH
THE MODELS POTENTIALLY OVER-FORECASTING THIS SWELL FOR THE NORTHWEST
CALIFORNIA COAST. EVEN THE GLOBAL WAVE DATA SHOWS ATTENUATION AND
DATA GAPS AS IT APPROACHES THE WEST COAST. FOR NOW I AM CONTENT
WITH THE NWPS OUTPUT WHICH CAPS THE SWELL AT 3 FT AND NO
SIGNIFICANT IMPACTS EXPECTED TOWARDS SOUTHWARD FACING BEACHES AND
ANCHORAGES. HOWEVER, THIS WILL NEED TO BE MONITORED IN CASE THE
SWELL HEIGHT IS LARGER. KML

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
     FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM PST SUNDAY FOR
     CAZ001-002-076.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 3 AM PST SUNDAY FOR PZZ455.

     SMALL CRAFT ADVISORY UNTIL 3 AM PST SUNDAY FOR PZZ410-450.

     HAZARDOUS SEAS WARNING FROM 3 PM THIS AFTERNOON TO 3 AM PST
     SUNDAY FOR PZZ410-450.

     SMALL CRAFT ADVISORY UNTIL NOON PST TODAY FOR PZZ470.

     GALE WARNING FROM NOON TODAY TO 3 AM PST SUNDAY FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 4 AM PST WEDNESDAY FOR PZZ475.

     HAZARDOUS SEAS WARNING FROM 3 PM THIS AFTERNOON TO 3 AM PST
     SUNDAY FOR PZZ475.

&&

$$

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