Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 241130
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
430 AM PDT THU APR 24 2014

.SYNOPSIS...
WET WEATHER WILL CONTINUE TODAY AS A WEAK FRONT IMPACTS NORTHERN
CALIFORNIA. AN UPPER LEVEL TROUGH WILL INTRODUCE A COLDER AND MORE
UNSTABLE AIRMASS TO THE REGION...RESULTING IN A SLIGHT CHANCE FOR
THUNDERSTORMS ON FRIDAY. A BRIEF PERIOD OF DRY WEATHER WILL RETURN
LATE ON FRIDAY...FOLLOWED BY MORE RAIN ON THE WEEKEND.

&&

.DISCUSSION...A WEAK COLD FRONT IS CURRENTLY MOVING ACROSS THE
NORTH COAST THIS MORNING PROVIDING LIGHT RAIN TO AREAS NORTH OF
THE EEL RIVER. THIS FRONT WILL CONTINUE TO SWING WESTWARD WHILE THE
RAIN BAND GRADUALLY SAGS SOUTH. BY THIS AFTERNOON THE FRONT WILL HAVE
EXITED THE AREA BUT SHOWER ACTIVITY WILL CONTINUE INTO THE EVENING.
THE UPPER LEVEL TROUGH WILL CONTINUE DIG SOUTHWARD OVER NORTHERN
CALIFORNIA INTRODUCING A COLDER AND MORE UNSTABLE AIRMASS
CONDUCIVE TO THUNDERSTORM DEVELOPMENT ON FRIDAY. UPPER LEVEL
DYNAMICS FAVOR A MORE UNSTABLE ENVIRONMENT WITH POSITIONING OF THE
UPPER LEVEL JET PROMOTING DIVERGENCE ALOFT. THE BEST LOW LEVEL
FORCING WILL OCCUR EARLY FRIDAY MORNING THROUGH THE LATE MORNING
AS THE TROUGH AXIS TRAVERSES NORTHERN CALIFORNIA. MUCAPE REMAINS
IN THE LOWER HUNDREDS WITH MARGINAL LIFTED INDICES BARELY DROPPING
TO -1 C. THE COLDER AIRMASS WILL ENCOURAGE HAIL DEVELOPMENT WITH
500 MB TEMPERATURES RANGING FROM -28 TO -31 DEGREES CELSIUS WITH
THE PASSAGE OF THE TROUGH. CONDITIONS WILL QUICKLY STABILIZE AS
RIDGING BUILDS BEHIND THE TROUGH AXIS PUTTING A HALT TO
THUNDERSTORM DEVELOPMENT BY FRIDAY EVENING. MODELS APPEAR TO BE IN
GOOD AGREEMENT WITH PRECIP WINDING DOWN FRIDAY NIGHT THROUGH
SATURDAY AS A BROAD FLAT RIDGE DEVELOPS IN THE WAKE OF THE TROUGH.
HOWEVER...ANOTHER WEAKER FRONT MAY BRING LIGHT AMOUNTS OF PRECIP
SATURDAY NIGHT INTO EARLY SUNDAY MORNING. WE SHOULD SEE BETTER
DRYING AND WARMING EARLY NEXT WEEK AS STRONGER RIDGING DEVELOPS
BOTH AT THE SURFACE AND ALOFT. THE GFS MODEL NOW COMING MORE IN
LINE WITH THE EURO FOR THE MID WEEK PERIOD WITH THIS RIDGING
AS WELL AS DEPICTING SOME WEAK OFFSHORE FLOW ON TUE AND WED. THUS
HAVE BUMPED TEMPERATURES UP AS WELL AS REMOVED CLOUD COVER DURING
THIS PERIOD. JT/KML/DB

&&

.AVIATION...A COLD FRONT WILL BRING A BAND OF RAIN WITH IFR TO MVFR
CONDITIONS THIS MORNING. CONDITIONS WILL LIKELY IMPROVE ALONG THE
COAST THIS AFTERNOON AND TONIGHT AS OPEN CELL CUMULUS MOVES TOWARD
THE COAST. LOW CLOUDS MAY BECOME TRAPPED OVER THE INTERIOR
MOUNTAINS THROUGHOUT THE DAY. AS AN UPPER LEVEL LOW MOVES OVERHEAD
TONIGHT INTO FRIDAY...SHOWER ACTIVITY WILL ONCE AGAIN INCREASE WITH
THE STRONGEST SHOWERS CAPABLE OF PRODUCING SMALL HAIL. AN ISOLATED
THUNDERSTORM IS ALSO NOT OUT OF THE QUESTION. RPA


&&

.MARINE...A COLD FRONT WILL MOVE THROUGH THE WATERS EARLY THIS
MORNING ALLOWING SOUTHERLY WINDS TO DECREASE AND LIGHT TO MODERATE
NORTHERLIES TO INCREASE THROUGH FRIDAY NIGHT. A LONG PERIOD WESTERLY
SWELL WILL BUILD INTO THE WATERS TODAY AND TONIGHT ORIGINATING FROM
A STORM SYSTEM IN THE NORTH-CENTRAL PACIFIC. SEAS ARE EXPECTED TO
REMAIN BELOW 10 FEET...SO NO SMALL CRAFT ADVISORIES ARE EXPECTED FOR
THIS SWELL.

THE NEXT COLD FRONT WILL MOVE THROUGH THE WATERS SATURDAY NIGHT
BRINGING A BRIEF PERIOD OF MODERATE TO STRONG SOUTHERLIES. THE
COASTAL JET IS CURRENTLY ANTICIPATED TO REMAIN RATHER WEAK WITH 925
MB WINDS AROUND 30 KT...SO WINDS SHOULD REMAIN BELOW GALE. A STRONG
UPPER LEVEL RIDGE WILL BUILD BACK OVER THE WEST COAST BEHIND THIS
FRONT RESULTING IN INCREASING NORTHERLIES OVER THE WATERS FOR NEXT
WEEK.

THE FIRST SIGNIFICANT SOUTHERLY SWELL OF THE SEASON WILL BUILD INTO
THE WATERS THIS WEEKEND. ENP GUIDANCE INDICATES IT WILL PEAK
SOMEWHERE BETWEEN 3 AND 4 FEET AT 17-19 SECONDS. JASON-2 ALTIMETRY
INDICATES THE SWELL DOES EXIST BUT MAY BE DELAYED SEVERAL HOURS FROM
THE MODEL DATA. HAVE CONTINUED TO INDICATE THE SWELL AT 3 FEET IN
THE GRIDS BUT HAVE DELAYED ITS ONSET 6 HOURS. RPA


&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 2 PM PDT
THIS AFTERNOON PZZ470.

&&

$$

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