Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 231213
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
513 AM PDT TUE SEP 23 2014

.SYNOPSIS...A PATTERN CHANGE WILL BEGIN TODAY AS A TROUGH MOVES
OVER THE WEST COAST...BRINGING COOLER TEMPERATURES AND RAIN TO
NORTHWEST CALIFORNIA. EXPECT WIDESPREAD RAIN FROM LATE TODAY
THROUGH THURSDAY FOLLOWED BY THE THREAT OF SHOWERS CONTINUING INTO
THE WEEKEND.

&&

.DISCUSSION...LARGE UPPER LOW IS PRESENTLY LOCATED OVER THE E PAC
NEAR 46N/141W. DEEP PLUME OF MOISTURE IS NOTED ON H2O VAPOR SAT
LOOP ALL THE WAY INTO THE CENTRAL PAC WITH SPLIT FEEDS OF MOISTURE
FROM WELL INTO THE W PAC. THE LOW IS EXPECTED TO SLOWLY FILL THRU
THE END OF THE WORK WEEK AS THE TROF POSITION SHIFTS E TOWARD THE
PAC COAST. ALTHO THE LOW FILLS...THE TROF IS PROGGED TO REMAIN
HIGHLY AMPLIFIED. THE MAIN PLUME OF MOISTURE IS EXPECTED TO PIVOT
BUT REMAIN BASICALLY SITUATED OVER THE LOCAL AREA WITH THE MOST
PERSISTENT AND HEAVIEST PRECIP STILL EXPECTED OVER THE TERRAIN OF
DEL NORTE COUNTY WHERE STORM TOTALS IN EXCESS OF 3 INCHES ARE
LIKELY.

PRECIP WILL TRANSITION FROM STRATIFORM TO MORE SHOWERY BY THU.
MINIMAL MUCAPE VALUES ARE ANTICIPATED THRU THE PERIOD...SO HAVE
CONTINUED TO KEEP THUNDER OUT OF THE FORECAST. HAVE MADE MINOR
ADJUSTMENTS TO TEMPERATURES AND POPS INTO THE EXTENDED FORECAST
PERIOD. INTRODUCED A SLIGHT CHANCE POP TO THE LATE TUE TIME
PERIOD. /SEC

&&

.AVIATION...VFR CONDITIONS WILL CONTINUE TO PREVAIL TODAY AS AN
APPROACHING STORM SPREADS MOSTLY MID AND HIGH CLOUDS OVER THE
REGION. LOWER CLOUDS WILL MOVE INTO COASTAL DEL NORTE COUNTY FROM
TIME TO TIME WITH MVFR CIGS AND A FEW SHOWERS THROUGH THE DAY AT
KCEC. LOWERING CIGS AND REDUCED VSBYS WILL DEVELOP LATE TONIGHT
ALONG THE NORTH COAST AS THE FRONT ARRIVES. GUSTY SOUTH WINDS A
FEW THOUSAND FT ABOVE MEAN SEA LEVEL WILL ALSO DEVELOP TONIGHT.

&&

.MARINE...SEAS REMAINED QUITE LOW OVERNIGHT...AROUND 3 TO 5 FT WITH
DOMINANT PERIODS AROUND 10 SECONDS. SHORT PERIOD SEAS WILL TREND
UPWARD TODAY THROUGH TONIGHT AS SOUTHERLY WINDS INCREASE AHEAD OF AN
APPROACHING FRONTAL SYSTEM. WINDS AND SEAS CONTINUE TO LOOK
STRONGEST NORTH OF CAPE MENDO AND IN THE OUTER WATERS. A SMALL CRAFT
ADVISORY FOR WINDS AND HAZARDOUS SEAS REMAINS IN EFFECT FOR PZZ470
FOR TODAY AND TONIGHT. SEAS WILL GO UP IN ALL ZONES ON WED AS
WESTERLY SWELL FROM A VIGOROUS FALL STORM ARRIVES. ASCAT PASS
CONFIRMED 40-50 KT WNW WINDS WITH THE STORM CENTERED ABOUT 900 MILES
TO THE NW OF EUREKA. I WILL CONTINUE TO FOLLOW THE WAVE MODEL
GUIDANCE WHICH HAS THE SWELL PEAKING TO 13 TO 15 FT NEAR 15 SECONDS
WED AFTERNOON AND EVENING. IT COULD COME IN HIGHER...BUT UNTIL MORE
DATA BECOMES AVAILABLE THERE IS NO WAY TO KNOW FOR SURE.

THE WAVE MODEL GUIDANCE CONTINUES TO SHOW SEAS TRENDING DOWNWARD ON
THU. SEE NO REASON AT THIS POINT TO DEVIATE FROM THE GUIDANCE. IT
WILL STILL REMAIN ELEVATED AND STEEP. THE MODELS CONTINUE TO
INDICATE A COUPLE OF SURFACE TROUGHS CLIPPING THE NORTHERN ZONES THU
INTO FRI. DIRECT OUTPUT FROM THE MODELS HAS WINDS MOSTLY AROUND 15
KT. BEEFED UP THE WINDS SLIGHTLY ABOVE THE MODEL OUTPUT. CONFIDENCE
AT THIS POINT IS NOT HIGH WE WILL SEE WINDS OF 20-25 KT. GFS
CONTINUES TO CONSISTENTLY TREND TOWARD INCREASING N-NWLY WINDS THIS
WEEKEND. THE ECMWF HAS BEEN WEAKER WITH THE N-NW WINDS...SO BLENDED
IN SOME OF THE LIGHTER ECMWF WINDS INTO THE FORECAST.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
 SMALL CRAFT ADV FROM 5 AM WED TO 9 PM THU FOR PZZ450.
 SMALL CRAFT ADV FROM 9 AM THIS MORNING TO 9 PM THU FOR PZZ470.
 SMALL CRAFT ADV FROM 8 AM WED TO 9 PM THU FOR PZZ455.
 SMALL CRAFT ADV FROM 2 PM THIS AFTERNOON TO 9 PM THU FOR PZZ475.

&&

$$

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