Area Forecast Discussion
Issued by NWS Eureka, CA

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000
FXUS66 KEKA 241136
AFDEKA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
436 AM PDT FRI OCT 24 2014

.SYNOPSIS...A FAIRLY NICE DAY IS EXPECTED TODAY AS A WARM FRONT
LIFTS OUT TO THE NORTH. HOWEVER...A POTENT COLD FRONT WILL BRING
RAIN AND STRONG WINDS TO NW CALIFORNIA OVERNIGHT AND INTO
SATURDAY. THIS WILL BE FOLLOWED BY POST FRONTAL SHOWERS AND A
THREAT OF THUNDERSTORMS. CONDITIONS WILL IMPROVE ON SUNDAY.

&&

.SHORT TERM (TODAY THROUGH MONDAY)...A WARM FRONT IS LIFTING
NORTHWARD OUT OF NW CAL THIS MORNING, BUT NOT BEFORE BRINGING
LIGHT RAIN TO DEL NORTE AND NORTHERN HUMBOLDT COUNTIES. MORNING IR
SATELLITE SHOWS SOME CLEARING BEGINNING TO OCCUR IN SOUTHERN
MENDOCINO BEHIND THIS WARM FRONT, AS HIGH PRESSURE RIDGES INTO THE
REGION. THIS CLEARING SHOULD WORK ITS WAY NORTH THROUGH THE DAY
ALLOWING FOR TODAY TO BECOME A FAIRLY NICE DAY...ALBEIT
INCREASINGLY WINDY.

THE APPROACHING COLD FRONT FOR TONIGHT IS THE MAIN STORY OF THE
FORECAST. MODELS HAVE COME INTO GOOD AGREEMENT WITH TIMING OF THE
RAIN, WHICH SHOULD ARRIVE AT THE COAST AROUND MIDNIGHT THEN SPREAD
EASTWARD. RAIN WILL LIKELY BE HEAVY AT TIMES. CONTINUE TO USE QPF
FROM CNRFC AS THE BASE, BUT HAVE BEEN SUPPLEMENTING WITH THE GFS
AND EC TO HELP SHOW HIGHER AMOUNTS OF QPF WITH THE STRONGEST
PORTIONS OF THE FRONT. THE NAEFS ANOMALY TABLE SHOW THE IVT IS
OVER 4 STANDARD DEVIATIONS ABOVE NORM OFF THE COAST OVERNIGHT
WHILE THE GFS AND GEFS IVT IS SHOWING VALUES WELL OVER 700, WHICH
PUTS US SQUARE IN AN ATMOSPHERIC RIVER. THIS WILL BRING COPIOUS
AMOUNTS OF PRECIP TO NW CAL TONIGHT INTO SATURDAY WITH TOTALS
RANGING FROM ABOUT AN INCH ACROSS THE DEEP INTERIOR VALLEYS TO
UPWARDS OF 4 TO 5 INCHES IN THE KING RANGE AND SISKIYOUS.

MORNING WATER VAPOR OVER THE EASTERN PACIFIC SHOWS A DIGGING AND
INTENSIFYING LOW WELL WEST OF THE BAY AREA. THIS LOW WILL
CONTINUE TO DEEPEN THEN TURN TO THE NE THIS AFTERNOON AND HEAD
TOWARD THE PAC NW AS IT DROPS AROUND 20MB IN 24 HOURS. AS THE
TRAILING FRONT APPROACHES THE COAST WINDS WILL INCREASE SHARPLY.
THE EC/NAM/GFS ALL SHOW 925 AND 850 WINDS INCREASING TO OVER 50KT
OVERNIGHT ALONG THE COAST AND TO AROUND 40KT AT 850 INLAND. THIS
WILL TRANSLATE TO VERY WINDY CONDITIONS ACROSS THE MOUNTAINS WITH
COASTAL RIDGES POTENTIALLY GUSTING DEEP INTO THE 60 MPH RANGE. THE
COASTAL PLAINS WILL ALSO BE GUSTING UP INTO THE 30 MPH WITH
ISOLATED AREAS REACHING 40 MPH. INTERIOR RIDGES WILL GUST INTO THE
40 MPH RANGE WHILE THE INTERIOR VALLEYS WILL REMAIN SOMEWHAT
SHELTERED WITH WINDS ONLY AROUND 10 TO 20 MPH. ASCENDING OUT OF
THE VALLEYS, WINDS WILL INCREASE SHARPLY. AS SUCH, HAVE HOISTED A
WIND ADVISORY FOR ALL OF NW CAL WITH INTERIOR AREAS CONFINED TO
THE MOUNTAINS. IMPACTS FROM THESE HIGH WINDS CAN RANGE FROM TRAVEL
HAZARDS TO DOWNED TREES AND POWER OUTAGES. IF OUT TONIGHT IN THE
WINDS, PLAN AHEAD AND STAY SAFE. IT IS BEST TO AVOID TRAVEL IN THE
WIND AND RAIN IF AT ALL POSSIBLE.

BEHIND THE COLD FRONT TONIGHT A COOL POOL AND POTENT POST FRONTAL
TROUGH WILL CROSS THE REGION ON SATURDAY. THIS WILL BRING THE
THREAT OF THUNDERSTORMS ACROSS THE REGION. THESE STORMS WILL HAVE
THE ABILITY TO MIXED DOWN STRONG WINDS FROM ALOFT CAUSING GUSTY
ERRATIC WINDS, AS WELL BRING SMALL HAIL, HEAVY RAIN OR MOUNTAIN
SNOW, AND OCCASIONAL LIGHTNING. SPC HAS PLACED NW CAL IN A
MARGINAL RISK FOR SEVERE, MAINLY FOCUSING ON THE WINDS, BUT WITH
THE SHEAR PRESENT IN THE VERTICAL AND THE POTENT TROUGH THEY SAY
IN THEIR DISCUSSION THAT "EVEN A BRIEF TORNADO APPEARS POSSIBLE".
WE WILL BE WATCHING CONDITIONS CLOSELY TODAY TO SEE HOW THIS
APPROACHING LOW SHAPES UP AND WHERE IT ULTIMATELY MAKES LANDFALL.
THIS WILL DICTATE WHERE THE POST FRONTAL TROUGH LANDS STRONGEST.

OVERALL, A NICE DAY TODAY FOLLOWED BY A WINDY AND RAINY NIGHT AND
EARLY SATURDAY. SATURDAY MORNING AND AFTERNOON WILL BRING A THREAT
OF THUNDERSTORMS AND POSSIBLE SEVERE. THIS WILL BE FOLLOWED BY A
NICE RIDGE WITH DRYING AND EASING CONDITIONS FOR SUNDAY INTO
MONDAY. BFG

.LONG TERM (TUESDAY THROUGH FRIDAY)...MOIST ZONAL FLOW AND ANOTHER
FRONTAL SYSTEM ON TUE WILL PROBABLY GENERATE MORE RAIN IN THE
NORTHERN ZONES WITH LESS OF A CHANCE IN THE SOUTHERN ZONES. LITTLE
OR NO CHANGES WERE MADE TO THE FORECAST HERE. GFS AND ECMWF START
TO DIVERGE ON WED AND THU AS THE FLOW AMPLIFIES AND ANOTHER UPPER
TROUGH SLOWLY APPROACHES THE COAST. MODELS WERE NOT IN REAL GOOD
SYNC...BUT IT DOES LOOK LIKE MILD AND PERHAPS WET WEATHER
CONDITIONS WILL PERSIST NEXT WEEK. BOOSTED PRECIP CHANCES SOME BUT
STILL NOT CONFIDENT ENOUGH AT THIS POINT TO GO MORE THAN 50% EVEN
IN DEL NORTE COUNTY.

&&

.AVIATION...A SHORT PERIOD OF MVFR OR IFR MAY OCCUR AT THE COASTAL
AIRPORTS AS HIGH PRESSURE BUILDS IN BEHIND THE WARM FRONT LIFTING
OUT TO THE NORTH. OTHERWISE, COASTAL AIRPORTS SHOULD REMAIN VFR.
UKI HAS BEEN SOCKED IN WITH LOW CLOUDS AND LOW VSBY THIS MORNING
AS SOUTHERLY FLOW HAS CREPT THEM INTO THE VALLEY. AS THE SUN COMES
UP THIS SHOULD MIX OUT READILY, LEAVING THEM VFR FOR THE DAY.
TONIGHT WILL BE THE MAIN STORY WITH AN APPROACHING COLD FRONT,
BRINGING STRONG SOUTHERLY WINDS TO THE COAST AND LOWERING VSBY IN
HEAVY SHOWERS. THE PEAK OF THE ACTIVITY SHOULD BE OVERNIGHT INTO
THE EARLY DAYLIGHT HOURS OF SATURDAY. THERE WILL BE AMPLE VERTICAL
SPEED SHEAR AHEAD OF THE FRONT AND POSSIBLE DIRECTIONAL SHEAR
BEHIND THE FRONT. TAFS REFLECT AN IMPROVING DAY TODAY AND
DETERIORATING CONDITIONS TONIGHT. BFG

&&

.MARINE...VIGOROUS LOW PRESSURE SYSTEM WILL SPIN UP OFFSHORE
TODAY. WINDS WILL RAMP UP THIS AFTERNOON AND EVENING...HOWEVER
THE STRONGEST WINDS WILL MOST LIKELY ARRIVE LATE TONIGHT INTO
SATURDAY MORNING WITH THE COLD FRONT. GUSTS UP TO 50 KT WILL BE
POSSIBLE EITHER LATE TONIGHT OR EARLY SATURDAY...MAINLY NEAR
CAPE MENDO. A POST FRONTAL TROUGH MAY ALSO KICK UP THE WINDS
SAT AFTERNOON AS INSTABILITY INCREASES IN THE COOLER AIR BEHIND
THE FRONT. NWPS HAS SHORT PERIOD SEAS HITTING 15 TO 20 FT LATE
TONIGHT INTO SAT MORNING. SEE NO REASON TO GO AGAINST THE MODEL
AT THIS POINT. GALE WARNINGS HAVE BEEN POSTED FOR ALL
MARINE ZONES...STARTING THIS AFTERNOON IN THE OUTER WATERS
AND THEN EXPANDING INTO THE INNER WATERS LATE TONIGHT.

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...     WIND ADVISORY FROM 2 AM TO 5 PM PDT SATURDAY FOR CAZ001.

     WIND ADVISORY FROM 2 AM TO 2 PM PDT SATURDAY FOR CAZ002-076.

     WIND ADVISORY FROM 11 PM THIS EVENING TO 5 PM PDT SATURDAY FOR
     CAZ003.

     WIND ADVISORY FROM 2 AM TO 11 AM PDT SATURDAY FOR CAZ004.

NORTHWEST CALIFORNIA COASTAL WATERS...
     SMALL CRAFT ADVISORY FROM NOON TODAY TO 4 PM PDT THIS AFTERNOON
     FOR PZZ470.

     GALE WARNING FROM 4 PM THIS AFTERNOON TO 9 PM PDT SATURDAY FOR
     PZZ470-475.

     SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 4 PM PDT THIS
     AFTERNOON FOR PZZ475.

     SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 2 AM PDT
     SATURDAY FOR PZZ455.

     GALE WARNING FROM 2 AM TO 9 PM PDT SATURDAY FOR PZZ450-455.

     SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 2 AM PDT SATURDAY
     FOR PZZ450.

&&

$$

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