Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 042230
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
330 PM PDT MON MAY 4 2015

.SYNOPSIS...AN UPPER TROUGH WILL DIVE SOUTH OVER CALIFORNIA THIS
WEEK HOWEVER CONDITIONS WILL REMAIN MOSTLY DRY WITH ONLY A FEW
ISOLATED SHOWERS OVER THE INTERIOR MOUNTAINS. TEMPERATURES SHOULD
CONTINUE TO BE SEASONAL OVER THE NEXT FEW DAYS.

&&

.DISCUSSION...THE MARINE INVERSION HAS WEAKENED SIGNIFICANTLY THIS
AFTERNOON AS A WEAKENING FRONT APPROACHES THE COAST. THIS HAS
ALLOWED THE STRATUS TO MIX OUT ALONG THE IMMEDIATE COAST BUT ALSO
HAS PUSHED THE STRATUS INTO THE NEAR COAST MOUNTAINS. ACROSS THE
INTERIOR FLAT CUMULUS HAS FORMED OVER THE MOUNTAINS. A RATHER STRONG
MID-LEVEL INVERSION SHOULD RESTRICT SHOWER OR THUNDERSTORM
DEVELOPMENT THIS AFTERNOON/EVENING...HOWEVER THERE IS STILL A SLIGHT
CHANCE OF A STORM IF CONDITIONS WERE TO LINE UP PERFECTLY SO HAVE
OPTED TO KEEP THE FORECAST FOR THE REMAINDER OF THE AFTERNOON AND
EVENING THE SAME.

AS THE FRONT MOVES ONTO THE COAST TONIGHT THE STRATUS SHOULD
REDEVELOP AND PUSH FARTHER INLAND...POSSIBLY EVEN INTO THE TRINITY
COUNTY VALLEYS. THUS CLOUD COVER HAS BEEN INCREASED ACROSS MUCH OF
THE AREA FOR TONIGHT THROUGH TUESDAY MORNING. EVER SO SLIGHTLY
COOLER AIR WILL MOVE OVER NORTHWEST CALIFORNIA ON TUESDAY RESULTING
IN TEMPERATURES A FEW DEGREES LOWER THAN THE LAST FEW DAYS/NIGHTS.
CONSIDERING A FEW INTERIOR VALLEYS HAVE BEEN PUSHING FROST ADVISORY
CRITERIA TEMPERATURES THE LAST COUPLE OF NIGHTS...THERE IS POTENTIAL
FOR TRINITY AND NORTHERN MENDOCINO VALLEYS TO REQUIRE FROST
ADVISORIES TUESDAY AND WEDNESDAY NIGHTS WITH DRIER AIR IN PLACE AND
MOSTLY CLEAR SKIES.

AN UPPER LEVEL LOW WILL MOVE DOWN THE WEST COAST WEDNESDAY INTO
THURSDAY. THIS WILL BEGIN TO INCREASE HIGH LEVEL CLOUD COVER OVER
THE REGION...AND DEPENDING ON THUNDERSTORM DEVELOPMENT TO THE
NORTHEAST...MAY BECOME THICK ALOFT. THUS OVERNIGHT LOW TEMPERATURES
HAVE THE POTENTIAL TO BE A FEW DEGREES WARMER THURSDAY NIGHT.
CONVECTIVE PARAMETERS CURRENTLY DO NOT LOOK AMAZING THURSDAY AND
FRIDAY AFTERNOONS OVER NORTHWEST CALIFORNIA WITH DRY NORTHERLY FLOW.
HAVE OPTED TO REMOVE RAIN CHANCES FOR COASTAL AREAS BUT KEPT THE
SLIGHT CHANCE TO CHANCE POPS OVER THE INTERIOR MOUNTAINS.

THE UPPER LOW WILL MOVE EAST OF THE AREA OVER THE WEEKEND LEAVING A
WEAK RIDGE OVER NORTHWEST CALIFORNIA ON SATURDAY. THERE ARE
CONSIDERABLE MODEL DISCREPANCIES BEYOND SATURDAY WITH THE GFS AND
ECMWF BOTH BRINGING ANOTHER UPPER LEVEL LOW INTO THE REGION BUT AT
DIFFERING TIMES AND STRENGTHS. FOR NOW HAVE LEFT THE FORECAST
UNCHANGED WITH SLIGHT CHANCE TO CHANCE POPS OVER MUCH OF THE REGION.
/RPA


&&

.AVIATION...STRATUS WAS FOUND WELL INLAND THIS MORNING WITH A DEEP
MARINE LAYER AND CLOUD TOPS NEAR 3K FEET AS REPORTED BY A PIREP VC
KACV THIS MORNING. AS OF 21Z...VISIBLE SATELLITE IMAGERY SHOWED
STRATUS DECREASING OVER DEL NORTE AND HUMBOLDT COUNTIES...WITH SOME
CU BUILDING OVER THE INTERIOR MOUNTAINS. A FEW HOURS OF VFR ARE
POSSIBLE FOR COASTAL LOCATIONS THIS AFTERNOON AND EVENING. GOING
INTO THE OVERNIGHT...VFR TO MVFR CIGS ARE POSSIBLE AGAIN FOR COASTAL
SITES. FORECAST IS TRICKY TONIGHT AS DRIER AIR BUILDS IN BEHIND A
WEAK FRONTAL BOUNDARY PROGGED TO MOVE ACROSS THE AREA THIS EVENING.
FOR NOW...HAVE KEPT MVFR CIGS IN FOR KCEC AND KACV...BUT WOULDN`T BE
SURPRISED IF CLOUDS STRUGGLE TO FORM. ACROSS THE INTERIOR...BESIDES
SOME CU BUILDUPS THIS AFTERNOON...MAINLY VFR IS EXPECTED.


&&

.MARINE...6 TO 8 FOOT SEAS HAVE BEEN REPORTED AT THE NEAR SHORE
BUOYS THIS AFTERNOON WITH NORTHERLY WINDS OF 10 TO 25 KT BEING
OBSERVED...STRONGEST SOUTH OF CAPE MENDOCINO. A WEAK FRONTAL
BOUNDARY WILL PASS THROUGH THE WATERS THIS EVENING...REPLACED BY
HIGH PRESSURE BUILDING IN BEHIND THE FRONTAL PASSAGE. THE PRESSURE
GRADIENT WILL TIGHTEN AND WINDS AND SHORT PERIOD SEAS WILL INCREASE
IN RESPONSE. SOUTHERLY SWELL CONTINUES TO MOVE THROUGH THE WATERS
TODAY WITH WAVES AT 4 FT AROUND 20 SECONDS. AT THE SAME TIME...A
NORTHWESTERLY SWELL WILL BUILD INTO THE WATERS AND CONTINUE TO
PROPAGATE ACROSS THE WATERS THROUGH THE WEEK KEEPING SEAS ELEVATED.
KEPT THE SMALL CRAFT ADVISORY GOING FOR THE SOUTHERN OUTER WATERS
AND HOISTED SMALL CRAFT ADVISORIES FOR THE SOUTHERN INNER WATERS AND
NORTHERN OUTER WATERS FOR INCREASING NORTHERLY WINDS AND SEAS.


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY FROM 3 AM TUESDAY TO 3 AM PDT FRIDAY FOR
     PZZ470.

     SMALL CRAFT ADVISORY UNTIL 3 AM PDT FRIDAY FOR PZZ455.

     SMALL CRAFT ADVISORY UNTIL 3 AM PDT FRIDAY FOR PZZ475.

&&

$$

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