Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 270550
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
950 PM PST WED NOV 26 2014

.SYNOPSIS...HIGH PRESSURE OVER THE REGION WILL MAINTAIN DRY WEATHER
CONDITIONS THROUGH TONIGHT. A SERIES OF STORMS WILL BRING A RETURN
OF WET WEATHER CONDITIONS THROUGH THE THANKSGIVING WEEKEND.

&&

.UPDATE...LATEST 00Z MODELS NOW FAIRLY CONSISTENT FOR THANKSGIVING
WITH RAIN BEGINNING IN CRESCENT CITY AREA ABOUT 6-7AM. MODELS SAG
THIS FRONT SOUTH INTO THE REST OF DEL NORTE COUNTY BY LATE AFTERNOON
WITH SOME LIGHT RAIN AS FAR SOUTH AS TRINIDAD BEFORE PULLING IT BACK
TO THE WEST. THERE IS A SIGNIFICANT DIFFERENCE THOUGH IN RAINFALL
AMOUNTS WITH THE NAM MUCH WETTER THAN GFS THOUGH TIMING OF HEAVIEST
RAIN IN THE AFTERNOON IS ABOUT THE SAME. VERY SHARP RAINFALL
GRADIENT WITH VERY WET NAM FORECASTING ABOUT 0.60 IN THIS AFTERNOON
PERIOD AT CRESCENT CITY WITH ALMOST 1.5 INCHES NEAR SMITH RIVER. GFS
SHOWING ONLY ABOUT 0.10 AT CRESCENT CITY WITH SMITH RIVER ABOUT
0.20. NAM AND GFS FLIPPED AS TO WHICH WOULD BE WETTER MODEL COMPARED
TO THIS MORNING WHICH SHOWS UNCERTAINITY IS JUST WHERE THE FRONT
WILL STALL. WILL LEAVE GRIDDED FORECAST AS IS BUT WILL HAVE TO WATCH
WHERE FRONT STALLS AS SOMETHING CLOSER TO THE NAM WOULD GIVE LOCAL
STREET AND CREEK FLOODING. WILL UPDATE THE AVIATION FORECAST TO HOLD
OFF RAIN AT KACV AND KUKI UNTIL LATE THURSDAY NIGHT AND FRIDAY.

ELSEWHERE IN NORTHWEST CA, IT LOOKS DRY FOR THANKSGIVING EXCEPT FOR
LIGHT RAIN DEVELOPING IN FAVORED UPSLOPE AREAS LIKE HONEYDEW IN THE
AFTERNOON. FRONT PUSHES BACK EAST THROUGH ENTIRE AREA ON FRIDAY AS
PREVIOUSLY MENTIONED. DEAN

&&

.PREV DISCUSSION...ISSUED AT 329 PM...VARYING AMOUNTS OF HIGH CLOUDS
MOVED ACROSS THE AREA TODAY AS AN UPPER LEVEL RIDGE AXIS SHIFTED TO
THE EAST IN RESPONSE TO AN APPROACHING LOW PRESSURE SYSTEM. CLOUDS
WILL CONTINUE TO THICKEN UP AND LOWER THROUGH THE NIGHT AS A FRONTAL
SYSTEM APPROACHES THE WEST COAST. SATELLITE IMAGERY SHOWED THE
FRONTAL BAND JUST OUTSIDE 130W MOVING EASTWARD. GFS...ECMWF AND
NAM12 SHOW THE FRONT SLOWING DOWN AND STALLING NEAR THE CALIFORNIA-
OREGON BORDER ON THU. BOTH MODELS CONTINUE TO INDICATE RAIN
DEVELOPING IN DEL NORTE COUNTY BY AFTERNOON AS SOUTHERLY FLOW AND
WARM AIR ADVECTION INCREASES THROUGH THE DAY IN ADVANCE OF THE
FRONT. THE GFS HAS BEEN THE MOST BULLISH WITH THE RAINFALL AMOUNTS
OVER DEL NORTE COUNTY ON THU WITH UP TO 1.5 INCHES IN 12HRS. THE
ECMWF AND NAM12 HAVE BEEN MUCH LIGHTER...ABOUT 0.25IN PER THE ECMWF
AND ABOUT 0.15IN PER THE NAM12. LEANED TOWARD THE ECWMF AND
CNRFC/WPC QPF GUIDANCE WHICH HAS 0.50IN. IT WILL NEED TO BE
MONITORED CLOSELY FOR HIGHER RAIN AMOUNTS. IF THE GFS PANS OUT THE
SMITH RIVER COULD RISE RAPIDLY TO MONITOR STAGE. SOME PRECIP MAY
FORM SOUTH OF DEL NORTE IN THE WARM AIR ADVECTION AND UPSLOPE
SOUTHERLY FLOW...HOWEVER AMOUNTS SHOULD BE FAIRLY LIGHT AND SPOTTY.

THE MODELS WERE IN GOOD AGREEMENT SHOWING THE FRONT REMAINING NEARLY
STATIONARY NEAR THE OR-CA BORDER THU NIGHT...BEFORE A MID LEVEL
SHORT WAVE TROUGH PUSHES THE BOUNDARY ONSHORE ON FRIDAY. RAIN WILL
INCREASE THROUGHOUT THE REST OF THE FORECAST AREA FRIDAY INTO
FRIDAY NIGHT AS THE FRONT SLOWLY PROGRESSES SOUTHWARD THROUGH SAT
MORNING. THE STORM WILL BE DOMINATED BY SOUTHERLY WINDS AND WARM
AIR ADVECTION AND EXPECT SNOW LEVELS TO BE ABOVE ALL THE MAJOR
PASSES THROUGH SATURDAY; ABOVE 5500 TO 6000 FT THAT IS. RAINFALL
AMOUNTS ARE STILL SKETCHY FRIDAY INTO SATURDAY ACROSS THE AREA.
AN INCH OR SO WILL BE POSSIBLE. THE MODELS HAVE BEEN CONSISTENTLY
SHOWING A SECONDARY RAMP UP IN RAIN RATES FRIDAY NIGHT INTO
SATURDAY MORNING AS ANOTHER FRONTAL WAVE DEVELOPS. IT IS GOING TO
BE RAINY AND WET THROUGH SAT...SO ROCKSLIDES OR MUDSLIDES AND
LOCALIZED STREET FLOODING WILL BE POSSIBLE.

THERE MAY BE A BREAK IN STEADY RAIN SATURDAY AFTERNOON AND EVENING
BEFORE THE NEXT SURGE OF MOISTURE AND RAIN ARRIVES. THE GFS ONCE
AGAIN WAS THE MOST AGGRESSIVE AND THE FASTEST WITH SPREADING RAIN
BACK INTO THE AREA FROM THE SOUTH SAT NIGHT AND SUN. THE ECWMF WAS
ABOUT 6-12 HOURS SLOWER AND NOT QUITE AS HEAVY ON THE RAIN.
CONFIDENCE IS NOT HIGH WE WILL SEE A LOT OF RAIN DURING THIS TIME
PERIOD. THE NAM12 INDICATES STRONGER DRYING AND COOLING AS NORTHERLY
FLOW DEVELOPS ACROSS THE REGION BY SAT EVENING. THE NAM12 SCENARIO
SEEMS UNLIKELY. IF IT WERE TO PAN OUT...SUNDAY WILL END UP BEING
DRY TOO. FOR NOW SIDED WITH SPECTRAL MODELS WHICH MAINTAIN SOGGY
WEATHER CONDITIONS THROUGH THE DAY ON SUNDAY.

GFS AND ECMWF CONTINUE TO INDICATE A WET AND UNSETTLED WEATHER
PATTERN CONTINUING INTO THE EARLY PORTION OF NEXT WEEK. THE TIMING
AND DURATION OF THE RAIN ARE QUESTIONABLE AS BOTH THE GFS AND ECMWF
STRUGGLE FROM RUN TO RUN ON HOW QUICKLY TO MOVE THE UPPER TROUGH/LOW
EASTWARD. THE ECMWF HAS SLOWED IT DOWN. THE 0Z GFS HAS BEEN TRENDING
IN THAT DIRECTION AS WELL. CONFIDENCE REMAINS MODERATELY HIGH WE
WILL SEE A FEW MORE BOUTS OF LIGHT RAIN...MONDAY OR MONDAY
NIGHT...BUT LOW FOR MODERATE OR HEAVY RAIN. CONFIDENCE STARTS TO
FALL OFF TUESDAY INTO WEDNESDAY AS BOTH MODELS START TO PART
COMPANY AND GO THEIR SEPARATE WAYS. THE GFS HAS IT DRYING OUT BY
WED WHILE THE ECMWF CONTINUES WITH WET WEATHER. AVERAGED THE TWO
MODELS FOR EQUAL CHANCES OF RAIN OR NO RAIN.

&&

.AVIATION...AS OF 945 PM...HIGH CLOUDS ABOVE 15KT STREAMING OVER
AREA AHEAD OF FRONT. LIFR CIGS IN STRATUS AGAIN DEVELOPED IN FAVORED
VALLEY LOCATIONS LIKE THE TRINITY VALLEY. FRONT WILL BE SLOW TO MOVE
EAST BUT EXPECT LIGHT RAIN TO START AT KCEC ABOUT 6-7 AM WITH VFR
CEILINGS. FRONT CONTINUES TO SAG SOUTH AND LOOKING FOR MODERATE-
HEAVY RAIN AT KCEC WITH MVFR CIGS AFTER ABOUT 10 AM AND INTO THE
AFTERNOON. FRONT PULLS BACK SLIGHTLY OFFSHORE IN THE EVENING BUT
CIGS AT KCEC WITH REMAIN MVFR IN LIGHT RAIN. ELSEWHERE...VFR
CEILINGS EXCEPT IN THE RIVER VALLEYS WHERE THE STRATUS WILL BE SLOW
TO DISSIPATE AS HIGHER CLOUDS MOVE OVER THE AREA. LOOKING FOR RAIN
TO MOVE INTO KACV AFTER MIDNIGHT WITH VFR CIGS BECOME MVFR. DEAN

&&

.MARINE...AS OF 945 PM...NEARSHORE BUOYS REPORTED SEAS FROM 4 TO 7
FEET AS OF 04Z THIS EVENING. A WESTERLY SWELL WAS MOVING THROUGH THE
WATERS WITH SOUTHERLY WINDS AND SHORT PERIOD SEAS INCREASING IN
ADVANCE OF AN APPROACHING COLD FRONT. A FEW LIGHTNING STRIKES HAVE
BEEN NOTED ABOUT 100 TO 125 NM OFFSHORE THIS EVENING ON THE BACKSIDE
OF THE APPROACHING FRONT. HAVE HELD OFF ON INTRODUCING ANY THUNDER
TO THE OUTER WATERS AT THIS TIME AS MODEL GUIDANCE SHOWS MARGINAL
INSTABILITY REMAINING WEST OF THE OUTER WATERS. OTHERWISE THE
FORECAST REMAINS THE SAME AND THE PREVIOUS MARINE DISCUSSION IS
BELOW. STP

MODELS REMAIN IN GOOD AGREEMENT SHOWING A LARGE STORM SYSTEM
IMPACTING THE COASTAL WATERS FOR THE NEXT FEW DAYS. SOUTHERLY WINDS
WILL REMAIN ELEVATED THROUGH FRIDAY. LEFT THE SC.Y`S UNCHANGED FOR
THE OUTER WATERS, BUT ADDED ONE FOR ZONE 450 TO ACCOUNT FOR THE
BUILDING W SWELL IN THE NEXT 24 HOURS. SEAS WILL BE MIXED WITH A
BUILDING W SWELL ON THANKSGIVING, WHICH WILL GRADUALLY SUBSIDE INTO
THE WEEKEND, AND SHORT PERIOD WIND WAVES BUILDING TONIGHT AND
CONTINUING THROUGH FRIDAY. SATURDAY WINDS SHOULD EASE AND BECOME
NORTHERLY AS A DISTURBANCE TRIES TO PUSH THROUGH. HOWEVER, MODELS
ARE NOT IN GREAT AGREEMENT ON THE TIMING OF THE WIND SHIFT OR THE
STRENGTH OF THE WINDS. THIS FORECAST REFLECTS THE CONSENSUS OF THE
MODELS. AS WE GO INTO SUNDAY THE MODELS SHOW WINDS BECOMING
SOUTHERLY. BUT AGAIN THE STRENGTH OF THE WIND DIFFERS BASED ON THE
MODELS. ONCE AGAIN WENT WITH THE CONSENSUS OF THE MODELS. WAVES
SHOULD REMAIN ELEVATED EARLY NEXT WEEK. BUT HOW HIGH, DIRECTION,
STEEPNESS, ETC. IS TOO HARD TO DETERMINE AT THIS POINT GIVEN THE
VARIABILITY IN THE MODELS.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY FROM 3 PM THURSDAY TO 9 PM PST FRIDAY FOR
     PZZ450.

     SMALL CRAFT ADVISORY UNTIL 9 PM PST FRIDAY FOR PZZ470.

     SMALL CRAFT ADVISORY FROM 3 PM THURSDAY TO 9 PM PST FRIDAY FOR
     PZZ475.

&&

$$

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