Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 272336
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
336 PM PST FRI FEB 27 2015

.SYNOPSIS...A STORM SYSTEM WILL BRING RAIN SHOWERS...COOLER
TEMPERATURES AND SOME MOUNTAIN SNOW THROUGH SATURDAY. DRY
CONDITIONS ARE EXPECTED SUNDAY FOLLOWED BY ANOTHER STORM SYSTEM
WITH LIGHT RAIN SHOWERS MONDAY AND TUESDAY.

&&

.DISCUSSION...A WEAK UPPER LOW CONTINUES TO SLOWLY MOVE S ALONG
THE WA AND OR COASTLINE THIS AFTERNOON. MOST OF THE FORCING FOR
MORE WIDESPREAD RAINS HAS MOVED OUT OF THE AREA AND HAS BEEN
REPLACED WITH CONVECTIVE SHOWERS. THE CLOUD FIELD OVER THE PACIFIC
HAS BECOME STEADILY MORE OPEN CELLULAR THRU THE MORNING AND EARLY
AFTERNOON. CLOUDS OVER LAND HAVE BEEN MORE EXTENSIVE DUE TO
DAYTIME HEATING AND THE CLOUDS SPREADING A BIT BENEATH A WEAK
INVERSION AT AROUND 10K FT. CLOUDS OVER LAND SHOULD GRADUALLY THIN
OVERNIGHT...ALTHO PATCHY VALLEY AND COASTAL PLAIN FOG IS
LIKELY...PARTICULARLY IN RECENT RAIN AREAS. POPS MAY BE A BIT
OVERDONE TONIGHT...BUT ANOTHER SPOKE OF ENERGY ALOFT IS PROGGED TO
SWING DOWN FROM THE N ACROSS THE AREA OVERNIGHT. AS SNOW LEVELS
COME DOWN...1 TO 2 INCHES OF ACCUMULATING SNOW ARE POSSIBLE OVER
ELEVATIONS ABOVE 4000 FT. HAVE HELD OFF ON ISOLATED THUNDER UNTIL
EARLY MORNING AS UPPER LOW MOVES OVERHEAD. BOTH THE GFS AND NAM
INDICATE THE BEST CHANCE OF THUNDER WILL BE OVER THE INTERIOR
MAINLY S OF CAPE MENDO DURING THE DAYTIME ON SAT. AT THIS
TIME...THIS STILL LOOKS LIKE IT WARRANTS ONLY ISOLATED MENTION.

AS SKIES CLEAR THIS WEEKEND...NIGHTTIME LOWS WILL DROP INTO THE
30S OVER THE INTERIOR SUNDAY MORNING. THE GROWING SEASON IN THE
MENDOCINO INTERIOR ZONE BEGINS ON MARCH 1ST. IT APPEARS POSSIBLE
THAT SOME PROTECTED VALLEYS WILL SEE FROST...BUT WINDS AT HIGHER
ELEVATIONS WILL PROBABLY BE ENUF TO PREVENT FROST. MONDAY
MORNING...ALTHO A BIT WARMER...MAY SEE A BIT MORE FROST FORMATION.

ANOTHER WEAK SYSTEM DROPPING IN FROM THE N MAY BRING SOME
ADDITIONAL LIGHT RAIN TO THE AREA ON MONDAY AND MONDAY NIGHT.
MODELS CONTINUE TO BE BEARISH WITH THIS SYSTEM WITH LIGHT RAIN
AMOUNTS. HIGH PRESSURE WILL BUILD BACK INTO THE AREA ON WEDNESDAY
AND THURSDAY. ANOTHER SHOT OF RAIN IS POSSIBLE LATE IN THE WEEK.
/SEC

&&

.AVIATION...AT NORTH COAST AIRPORTS...BY LATE MORNING RAIN HAD
TURNED MOSTLY TO SHOWERS ACROSS THE REGION. MOST CIGS/VIS HAD
IMPROVED ALTHOUGH OCCASIONALLY CIGS AND VIS DROPPED TO MVFR IN
SHOWERS WITH A FEW INSTANCES OF IFR VIS IN A HEAVIER SHOWER AT
ACV. BY MID AFTERNOON...WIDESPREAD OPEN CELL CUMULUS CONTINUED TO
MOVE OVER NORTHWEST CALIFORNIA...THEREFORE PRODUCING WIDELY
SCATTERED SHOWERS OVER AIRFIELDS FROM THE COAST TO THE TRINITY
ALPS AND TO MIDDLE MENDOCINO. COOL AND SOMEWHAT UNSTABLE AIR WILL
CONTINUE TO MOVE INTO THE REGION. SCT-BKN MOSTLY VFR CONDITIONS
WILL CONTINUE ACROSS THE REGION WITH OCCASIONAL MVFR CIGS/VIS IN
SHOWERS. TSTMS POSSIBLE SATURDAY WITH MAX INSTABILITY. THREAT OF
CONVECTION SHOULD DIMINISH BY EARLY EVENING AS THE UPPER TROF MOVE
OUT OF THE AREA. TA

&&

.MARINE...MODERATE TO FRESH NORTHWESTERLY BREEZES WILL TO CONTINUE ACROSS MUCH
OF THE WATERS THROUGH THE LATE EVENING...BUT A COLD FRONT WILL CAUSE
WINDS TO VEER TO DUE NORTH OVERNIGHT.  AS A RESULT...SHORT PERIOD
SEAS ARE EXPECTED TO BUILD FROM 6 TO 8 FEET / 7 TO 8 SECONDS TO
AROUND 8 TO 11 FEET / 10 TO 11 SECONDS... WITH THE HEAVIEST SEAS
ACROSS THE OUTER WATERS WHERE A SMALL CRAFT ADVISORY REMAINS VALID
THROUGH SATURDAY NIGHT.  IN THE NORTHERN INNER WATERS...LIGHTER
WINDS WILL LIKELY PREVENT SHORT PERIOD SEAS FROM REACHING SMALL
CRAFT ADVISORY CRITERIA WITH THE EXCEPTION OF A LOCALIZED AREA NEAR
CAPE MENDOCINO AND HUMBOLDT BAY...AND THUS WILL CONTINUE TO HOLD OFF
ON ISSUING A SMALL CRAFT ADVISORY UNTIL LATER IN THE WEEKEND.  IN
THE SOUTHERN INNER WATERS...WINDS AND SEAS ARE RUNNING A BIT HIGHER
THAN THE NORTHERN INNERS...AND LIKEWISE THE SMALL CRAFT ADVISORY
REMAINS VALID.  OPTED TO EXTEND IT 6 HOURS TO 3 AM PST AS WELL TO
REFLECT LATEST WIND/WAVE GUIDANCE AND TRENDS...HOWEVER THE SHIFT IN
WINDS OVERNIGHT SHOULD PULL THE STRONGER WINDS FARTHER OFFSHORE AND
ALLOW SEAS TO BECOME LESS STEEP. ALSO IN THE MIX IS A DIMINISHING
WESTERLY SWELL AT AROUND 2 TO 3 FEET AND 11 TO 12 SECONDS...BUT THIS
HAS MOSTLY BEEN MARGINALIZED BY THE STEEP SHORT PERIOD WAVES AND
WILL ONLY CONTINUE TO DECAY.

OVERNIGHT SATURDAY...A PASSING SHORTWAVE WILL HELP TO TIGHTEN THE
PRESSURE GRADIENT...BRINGING NORTHERLY GALES AND BUILDING SHORT
PERIOD SEAS TO PRIMARILY THE NORTHERN OUTER WATERS AND A SMALLER
PORTION OF THE SOUTHERN OUTER WATERS.  AS SUCH...OPTED TO HOIST A
GALE WATCH FOR THE NORTHERN OUTER WATERS FROM 00-12Z SUNDAY ACROSS
THE NORTHERN OUTER WATERS WHERE CONFIDENCE IS HIGHEST IN WIDESPREAD
GALES.  IN THE SOUTHERN OUTER WATERS...CONFIDENCE IS LOWER THAT
GALES WILL BE SEEN ACROSS THE MAJORITY OF THE WATERS...BUT STEEP
SHORT PERIOD SEAS LIKELY WILL.  THUS...OPTED TO ADD A HAZARDOUS SEAS
WATCH FOR THE SOUTHERN OUTER WATERS FOR THE SAME TIME PERIOD.
FINALLY...WHILE THE STRONGEST WINDS AND LARGEST SEAS WILL REMAIN IN
THE OUTER WATERS...OPTED TO ADD SMALL CRAFT ADVISORIES TO THE INNER
WATERS TO ACCOUNT FOR BUILDING SHORT PERIOD SEAS.  BEYOND
SUNDAY...ELEVATED CONDITIONS WILL LIKELY PERSIST THROUGH WEDNESDAY
UNTIL A BUILDING UPPER LEVEL RIDGE ALLOWS WINDS TO EASE. /BRC

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY FROM 4 PM SATURDAY TO 4 AM PST SUNDAY
     FOR PZZ410-450.

     GALE WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT
     FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 4 PM PST SATURDAY FOR PZZ470.

     SMALL CRAFT ADVISORY UNTIL 3 AM PST SATURDAY FOR PZZ455.

     SMALL CRAFT ADVISORY FROM 4 PM SATURDAY TO 4 AM PST SUNDAY
     FOR PZZ455.

     SMALL CRAFT ADVISORY UNTIL 9 AM PST SUNDAY FOR PZZ475.

     HAZARDOUS SEAS WATCH FROM SATURDAY AFTERNOON THROUGH LATE
     SATURDAY NIGHT FOR PZZ475.

&&

$$

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