Gale Watch 41, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
942 AM PST TUE NOV 27 2012

.SYNOPSIS...HIGH PRESSURE ALOFT ALONG WITH LOW LEVEL OFFSHORE FLOW
WILL CONTINUE THROUGH TONIGHT. LOOK FOR A LOW PRESSURE SYSTEM
OFFSHORE TO BEGIN IMPACTING THE REGION ON WEDNESDAY FOR THE
DEVELOPMENT OF LOCALLY WINDY CONDITIONS. UNSETTLED CONDITIONS WILL
CONTINUE THE REST OF THE WEEK IN RESPONSE TO A SERIES OF PACIFIC
STORMS MOVING ACROSS THE REGION.

&&

.SHORT TERM...
DENSE HIGH...ALONG WITH SOME MID LEVEL...CLOUDS BLANKETED THE CWA
THIS MORNING. THERE WAS SOME SUN PEEKING THROUGH THE THIN SPOTS IN
THE OVERCAST BUT...FOR THE MOST PART...SKIES WERE MOSTLY CLOUDY
ACROSS THE AREA. LOOK FOR FILTERED SUNSHINE THE REST OF TODAY...
ALTHOUGH SOME PLACES MIGHT SEE MORE CLOUDS THAN SUN.

THE LOW LEVEL OFFSHORE OR EASTERLY PRESSURE GRADIENT CONTINUED TO BE
A LITTLE TIGHTER THAN WHAT THE MODELS PREDICTED...HENCE THE LOCALLY
GUSTY WINDS WEST OF THE SUMMIT OF SNOQUALMIE PASS. THE PRESSURE
GRADIENT WILL TIGHTEN FURTHER LATER TONIGHT THROUGH WED MORNING FOR
THE POSSIBILITY OF LOCALLY WINDY CONDITIONS ACROSS THE EAST WIND
PRONE LOWLANDS SUCH NORTH BEND AND ORTING.

MEANWHILE...THE UPPER RIDGE AXIS WILL SHIFT EAST OF THE AREA LATE
TONIGHT AND EVEN FARTHER EAST ON WED. THIS WILL ALLOW A NEGATIVELY
TILTED UPPER TROF TO APPROACH FROM THE SOUTHWEST DURING THE DAY WED.
THE MODELS CONTINUED TO WAFFLE ON THE TIMING OF THE PRECIP ARRIVAL
AND WERE NOW SLOWER THAN THE PREVIOUS RUN. SINCE DRY EASTERLY FLOW
WILL PERSIST IN THE LOWER LEVELS OF THE ATMOSPHERE...INCLINED TO
THINK THAT THE ONSET OF THE PRECIP WILL MOST LIKELY BE MORE IN THE
AFTERNOON ACROSS MUCH OF THE INTERIOR. BY LATE IN THE DAY WED...IT
SHOULD BE RAINING OR SNOW /DEPENDING ON YOUR ELEVATION/ ACROSS THE
ENTIRE CWA.

THE TAIL END OF A WEAKENING WARM FRONT WILL MOVE ACROSS THE FAR
WESTERN PART OF THE CWA WED NIGHT. WILL NEED TO MONITOR THE STRENGTH
AND THE DEPTH OF THE COLD EASTERLY FLOW THROUGH THE PASSES AS THERE
IS A POSSIBILITY OF FREEZING RAIN...ESPECIALLY IN THE LOWER PASSES
WED NIGHT AND/OR THU MORNING. OTHERWISE...ANTICIPATE GUSTY SOUTHEAST
WINDS TO DEVELOP OVER PARTS OF THE COAST AND NORTH INTERIOR WED
NIGHT. SPEEDS COULD REACH ADVISORY CRITERIA OVER THESE AREAS.

EXPECT A COLD FRONT TO SWEEP ACROSS THE CWA ON THU FOR WET WEATHER
AND LOCALLY WINDY CONDITIONS.

.LONG TERM FROM THE PREV DISCUSSION...
EXTENDED MODELS IN GOOD AGREEMENT IN THE OVERALL
PATTERN DURING THE PERIOD WITH A LARGE UPPER LEVEL TROUGH REMAINING
OFFSHORE AND WEATHER SYSTEMS KICKING OUT OF THE TROUGH MOVING
THROUGH WESTERN WASHINGTON. SOME DIFFERENCES IN THE TIMING AND
INTENSITY OF THE SYSTEMS IN THE MODELS SO A GENERAL BROADBRUSH RAIN
AT TIMES OR RAIN LIKELY FORECAST WILL CONTINUE THROUGH THE EXTENDED
PERIOD. THE 00Z ECMWF HAS A 980 MB LOW MOVING THROUGH WESTERN
WASHINGTON SUNDAY MORNING WHICH WOULD RESULT IN WINDY CONDITIONS
ACROSS THE AREA BUT THE 00Z GFS AND CANADIAN RUNS ARE WEAKER AND
MUCH FURTHER SOUTH WITH THIS FEATURE SO FOR NOW WILL NOT GO WITH THE
ECMWF SOLUTION ON SUNDAY. FELTON

&&

.HYDROLOGY FROM THE PREV DISCUSSION...
THERE CONTINUES TO BE SOME MODEL DIFFERENCES IN THE TIMING AND
INTENSITY OF THE WEATHER SYSTEMS AFTER THURSDAY MORNING IN THE MODEL
RUNS. THE 00Z ECMWF HAS PUSHED THE HEAVIEST PRECIPITATION SOUTH OF
THE CWA ON FRIDAY AND AGAIN ON SUNDAY. STILL WITH A SERIES OF STORMS
MOVING THROUGH THE AREA IN THE NEXT WEEK IT IS POSSIBLE THAT THE
SKOKOMISH RIVER COULD FLOOD WITH THE FLOOD THREAT BEGINNING ON
FRIDAY AND LASTING THROUGH THE WEEKEND. FELTON

&&

.AVIATION...UPPER RIDGE OVER WRN WA THIS MORNING WILL MOVE INTO ERN
WA THIS AFTN. THIS WILL OPEN THE DOOR TO INCREASING SOUTHERLY FLOW
ALOFT. AFT 00Z...THIS WILL BRING UP INCREASING MID-HIGH LVL
MOISTURE. OFFSHORE PRES GRADIENTS WILL GREATLY LIMIT THE EXTENT OF
ANY CLOUDS BELOW 5000 FT MSL OVER THE INTERIOR THROUGH 18Z THU. RAIN
AND PERHAPS SOME MVFR CIGS WILL SPREAD ONTO THE COAST BTWN 12Z-18Z
ON THU MRNG. WITH MID-HI CLOUDS TONIGHT AND MDT-STG OFFSHORE
GRADIENTS...NOT EXPECTING FOG/LOW STRATUS AT ANY TAF SITES ON WED
MRNG.

KSEA...MERELY LOOKING AT FAIRLY THICK HIGH CLOUDS THROUGH 06Z THIS
EVNG. MID-LEVEL CLOUDS WILL START TO THICKEN AFT 06Z...BUT
INCREASING EASTERLY PRES GRADIENTS OFF THE CASCADES WILL ELIMINATE
THE POSSIBILITY OF CLOUDS AOB 050 THROUGH 18Z WED. CHC OF -RA WILL
START TO INCRS AFT 21Z WED WITH CIGS LOWERING BLO 050 AFT THE ONSET
OF RAIN.    HANER

&&

.MARINE...A SFC RIDGE HAS SETTLED OVER IDAHO WITH A DEEPENING SFC
LOW OFFSHORE NEAR 49N/142W. ELY PRES GRADIENTS ACROSS WRN WA HAVE
EASED A LITTLE BUT NOT QUITE ENOUGH TO DROP THE SCA FOR THE WEST
ENTRANCE TO THE STRAIT. WINDS MAY DROP BELOW SCA LEVELS FOR A FEW
HOURS LATE THIS AFTN AND EVNG...BEFORE THEY RISE AGAIN LATER THIS
EVNG.

THE DEEP UPPER LEVEL AND SFC LOW THAT HAS FORMED OVER THE NE PACIFIC
WILL DOMINATE THE WEATHER PATTERN WED THROUGH THIS WEEKEND. UPPER
LEVEL SHORTWAVE TROUGHS AND THEIR ASSOCIATED SFC FRONTS WILL ROTATE
AROUND THE MAIN LOW AND NE ACROSS WRN WA WED THROUGH SUN. LOOKS LIKE
THERE WILL BE ROUGHLY ONE SYSTEM EACH DAY. AT THIS POINT...THE FRONT
ARRIVING ON THU SHOULD BE MARGINALLY STRONGER THAN THE OTHER FRONTS.
WINDS ARE EXPECTED TO RISE OVER THE COASTAL WATERS TONIGHT...WITH
GALES FORECAST MOST CONFIDENTLY ON WED NIGHT AND THU WITH THE
STRONGER FRONT. THE SE EXPOSED INLAND WATERS MAY ALSO SEE GALES ON
THU...PRIMARILY THE EAST ENTRANCE AND N INLAND WATERS.  HANER/KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE WEST ENTRANCE TO THE
     STRAIT OF JUAN DE FUCA AND MUCH OF THE COASTAL WATERS UNTIL
     10 PM TONIGHT.

     GALE WATCH IN EFFECT FOR THE COASTAL WATERS AND WEST ENTRANCE
     TO THE STRAIT OF JUAN DE FUCA FROM WEDNESDAY AFTERNOON THROUGH
     THURSDAY MORNING.

&&

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