FXUS66 KEKA 262207
AFDEKA
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
207 PM PST SAT DEC 26 2009
.SYNOPSIS...A SLOW MOVING STORM SYSTEM WILL BRING SHOWERS TO ALL
OF NORTHWEST CALIFORNIA FOR THE REMAINDER OF THE WEEKEND.
&&
.DISCUSSION...FCST CHALLENGES A PLENTY AS MODELS HAVE STRUGGLED
MIGHTILY WITH THE CURRENT PATTERN. SEVERAL BANDS OF MODERATE TO
HEAVY RAIN ARE NOT FAR OFFSHORE THIS AFTERNOON AHEAD OF A
DEVELOPING SFC LOW NEAR 40N 130W. THE CONVECTIVE LOOK OF THIS
PRECIP LEADS TO BE BELIEVE THAT LOCALIZED RAINFALL AMOUNTS WILL
EXCEED 1 INCH. ADDITIONALLY...THERE IS THE POSSIBILITY OF
THUNDERSTORMS OFFSHORE AS A FRONT GETS CLOSER AND INSTABILITY
DECREASES WITH LAPSE RATES STEEPENING (AOB 7 C/KM IN THE MID LAYERS).
ONCE THIS INITIAL BAND PUSHES THROUGH THIS EVENING...MORE OF A
SHOWERY REGIME SHOULD TAKE HOLD FOR THE REMAINDER OF THE WEEKEND
AS THE MAIN UPPER LOW SLOWLY PASSES OVERHEAD.
THE EVENTUAL TRACK OF THIS UPPER LOW IS MUCH DIFFERENT THAN
ADVERTISED BY THE MODELS OVER THE PAST COUPLE OF DAYS. INSTEAD OF
THE MAIN ENERGY CURRENTLY ALONG 130W DIVING SOUTH...IT WILL TRACK
ALMOST DUE EAST. THIS IS DUE TO THE UPPER LEVEL RIDGE PINCHING OFF
IN SW CANADA FASTER THAN EXPECTED. ANOTHER CONSEQUENCE OF THE
UPPER LOW TRACKING OVERHEAD WILL BE COOLER TEMPS AND LOWER SNOW
LEVELS. WHILE SIGNIFICANT SNOW IS NOT EXPECTED...SEVERAL INCHES IS
NOT OUT OF THE QUESTION ABOVE 3000 FT MAINLY LATE TONIGHT THROUGH
SUN EVENING. IF YOUR TRAVEL PLANS INCLUDE MOUNTAINOUS
DRIVING...PLEASE CHECK THE LATEST ROAD CONDITIONS BEFORE YOU HEAD
OUT AND MONITOR THE LATEST FORECASTS.
ALTHOUGH THE HIGH CENTERED OVER THE CANADIAN PRAIRIE PROVINCES
WILL ALLOW THE LOW TO MOVE ACROSS NRN CA...IT WILL ALSO HOLD IT
UP. AS A RESULT...WE WILL HANG ONTO SHOWERS IN THE FCST THROUGH
MON. MODELS HAVE COME INTO BETTER AGREEMENT EARLY NEXT WEEK...AND
NOW ALL SHOW A FAST MOVING SHORTWAVE AND ASSOCIATED SFC FRONT
MOVING THROUGH TUE NIGHT. THE FCST WAS MASSAGED DURING THIS TIME
TO TRY AND PIN POINT THIS FEATURE. AS THE GFS ENSEMBLE HAS BEEN
HINTING AT FOR A FEW DAYS...RIDGING IS EXPECTED TO POKE UP OVER
THE E PAC ON WED. THE WHAT AND WHERE OF ANY PARTICULAR SYSTEM
SQUASHING THE RIDGE IS ALMOST IMPOSSIBLE TO TIME...BUT WE DID FEEL
CONFIDENT TO CUT BACK ON POPS DURING THE MIDWEEK TIME FRAME. JCA
&&
.MARINE...SE WINDS HAVE BEEN SUSTAINING TO MARGINAL SMALL CRAFT
ADVISORY LEVEL (15-25KT) PER BUOY OBS AND A FEW PASSING SHIP
REPORTS. STRONGEST THRUST OF WIND SHOULD OCCUR TONIGHT AS THE MAIN
FRONTAL ZONE SKIRTS ACROSS THE AREA. SATELLITE IMAGERY DID SHOW A
VERTICALLY STACKED LOW NEAR 42N 132W...WITH SEVERAL LINEAR CLOUD
FEATURES PIN-WHEELING ABOUT THE CENTER. GFS/NAM/ECWMF ENSEMBLE
BLEND HAS THE CORE OF THE LOW ALOFT MOVING CLOSER TO THE COAST
TONIGHT->SUNDAY AND THEN WEEBLE-WOBBLING IT ABOUT OFFSHORE THE
OREGON COAST SUNDAY NIGHT. WITH THE PROXIMITY OF THE COLD CORE
ALOFT AND A SLIGHT NEGATIVELY TILTED TROUGH ALOFT...SQUALLY-LIKE
CONVECTION IS NOT OUT OF THE QUESTION. ERRATIC WIND GUSTS OF 35 KT
MIXING DOWN TO MEAN SEA LEVEL SEEMS POSSIBLE...WITH GFS AND NAM12
MODEL DATA SHOWING 35-40KT IN THE LOWEST 5KFT ABOVE MEAN SEA
LEVEL.
OTHER ISSUE IS THE INCOMING LONG PERIOD WESTERLY SWELL. REG-ENP AND
SWAN-MOD HAVE BEEN 3-5 FEET TOO HIGH COMPARED TO BUOY OBS. LOWERED
SWELL HEIGHTS BY 2-3 FEET ACROSS THE BOARD. BUT...EVEN WITH SWELL OF
13-15 FT AT 15-17 SECONDS...WE COULD SEE 18-20 FOOT BREAKERS.
DID NOT DEPART MORE THAN 2-3 FT FROM THE ENP AND SWAN GUIDANCE SUN
AND MON...WITH ADDITIONAL WESTERLY WIND BURSTS AND WAVE GENERATION
EXPECTED BETWEEN BUOY #6 AND THE WEST COAST TODAY->SUN. DJB
&&
.AVIATION...AN OVERCAST HIGH CLOUDS SHIELD SEEMS TO HAVE INHIBITED
DEVELOPMENT OF IFR VIS/CIG THIS MORNING...ALTHOUGH OCCASIONAL MVFR
VIS FROM HUMBOLDT BAY TO TRINIDAD OCCURRED BY LATE MORNING. ACV
BRIEFLY FELL TO MVFR VIS EVEN AS THE TAF SITES CONTINUED TO REPORT
SKC THROUGH NOON. SOME LOWER CLOUDS AND LIGHT RAIN REACH EKA ABOUT
1130 AM WITH ACV FINALLY REPORTING LOWER CLOUDS (NO RAIN) AT 100 PM.
BY 200 PM -RA/RASH WAS IMMINENT AT ALL APRTS. THE APPROACHING
WEAKENING FRONTAL BOUNDARY WILL CONTINUE TO LOWERING CIG/VIS INTO
THE MVFR RANGE THIS EVENING AS THE RA/RASH INCREASES...GREATER
AMOUNTS FALLING TONIGHT AND EARLY MORNING AT THE APRT TERMINALS. TA
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY ALL WATERS.
&&
$$
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