Gale Warning 61, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 AM PST WED NOV 11 2015

.SYNOPSIS...NORTHWEST FLOW ALOFT WILL ALLOW SCATTERED SHOWERS OVER
WESTERN WASHINGTON TODAY AND TONIGHT. A STRONG FRONTAL SYSTEM WILL
BRING WET AND WINDY WEATHER THURSDAY AFTERNOON THROUGH SATURDAY.
RIVER FLOODING IS POSSIBLE. AN UPPER LEVEL TROUGH WILL BRING SHOWERS
ON SUNDAY. THE WEATHER WILL REMAIN UNSETTLED EARLY NEXT WEEK.

&&

.SHORT TERM...A PUGET SOUND CONVERGENCE ZONE HAS MOSTLY DISSIPATED
THIS MORNING BUT THERE ARE SCATTERED SHOWERS. JUDGING FROM WEBCAMS
THE SNOW LEVEL IS DOWN TO ABOUT THE SNOQUALMIE PASS LEVEL...3000
FEET. A FEW MORE INCHES OF MOUNTAIN SNOW ARE POSSIBLE IN SHOWERS
TODAY BUT THE SNOW ADVISORY WILL BE ALLOWED TO EXPIRE AT 10 AM.
TONIGHT WILL LIKELY BE DRY BUT WILL PROBABLY KEEP THE LOW CHANCE
POPS FOR RESIDUAL SHOWERS.

MODELS HAVE CONSISTENTLY STARTED A HEAVY RAIN EVENT ON THURSDAY
AFTERNOON. THE NAM AND GFS ARE IN GOOD AGREEMENT...KEEPING HEAVY
RAIN AT TIMES THURSDAY NIGHT THROUGH SATURDAY MORNING THEN MOVING
THE FRONTAL BAND SOUTH OUT OF THE AREA DURING THE DAY ON SATURDAY.
THERE HAVE BEEN SOME CHANGES OVER THE LAST FEW RUNS. ONE SIGNIFICANT
CHANGE IS THE MAIN PRECIPITATION AREA HAS SHIFTED NORTH SOMEWHAT.
WILL LOOK AT THIS IDEA IN MORE DETAIL FOR THE AFTERNOON FORECASTS.

QPF GRIDS WILL BE A BLEND OF MESOSCALE MODELS WHICH CURRENTLY GIVE
SIX TO EIGHT INCHES GENERALLY IN THE MOUNTAINS WITH SOME 10-13 INCH
BULLSEYES. THE LOWLANDS RECEIVE ONE TO TWO INCHES.

STRONG SOUTHERLY PRESSURE GRADIENTS WILL DEVELOP ON THURSDAY AND
CONTINUE THROUGH FRIDAY NIGHT. IT LOOKS LIKE WINDY CONDITIONS WILL
BE FAIRLY WIDESPREAD WITH SPEEDS 20-35 MPH AND GUSTS TO 40-45 MPH.
THOUGH THE WINDS DO NOT SEEM TO REACH HIGH WIND CRITERIA...THEY WILL
BE CLOSE TO HIGH WIND AT TIMES. THE RELATIVELY LONG DURATION OF THE
WIND...UP TO 24 HOURS...MAY BE AS IMPORTANT AS THEIR SPEED. BURKE

.LONG TERM...THE GFS MOVES THE HEAVY RAIN BAND SOUTH OF THE AREA
SATURDAY AFTERNOON WITH SIGNIFICANTLY COLDER AIR IN PLACE AFTER
THAT. THE EURO IS A LITTLE SLOWER IN MOVING THE PRECIPITATION OUT
BUT STILL BRINGS COLDER AIR INTO THE AREA SATURDAY NIGHT. THE NEXT
SYSTEM DUE AROUND TUESDAY LOOKS LIKE MORE OF A MOUNTAIN SNOW
PRODUCER THAN A HEAVY RAIN PRODUCER. WILL ALSO LOOK AT THIS MORE FOR
THE AFTERNOON. BURKE

&&

.HYDROLOGY...FLOODING IS UNLIKELY ON AREA RIVERS THROUGH THURSDAY.

THE FORECAST HEAVY RAINFALL FOR THURSDAY NIGHT THROUGH EARLY
SATURDAY WOULD CAUSE FLOODING ON MANY AREA RIVERS. THIS INCLUDES ANY
RIVERS FLOWING OFF THE CASCADES FROM THE NOOKSACK IN THE NORTH TO
THE COWLITZ IN THE SOUTH. ALSO ANY OLYMPIC PENINSULA RIVERS COULD
FLOOD IF THIS RAIN OCCURS. EVEN THE RIVERS OF SOUTHWEST WASHINGTON
SUCH AS THE CHEHALIS AND ITS TRIBUTARIES COULD FLOOD.

HEAVY RAIN WILL BEGIN OVER THE OLYMPICS THURSDAY AFTERNOON AND THEN
CONTINUE THROUGH FRIDAY NIGHT. RIVER FLOODING MAY BE POSSIBLE ON
SOME RIVERS FLOWING OFF THE OLYMPICS BY FRIDAY MORNING. HEAVY RAIN
BEGINS OVER THE CASCADES LATER THURSDAY NIGHT WITH FLOODING ON
CASCADE RIVERS POSSIBLE FRIDAY. A HYDROLOGIC OUTLOOK STATEMENT
COVERS THIS FOR NOW BUT A WIDESPREAD FLOOD WATCH WILL GO OUT
TODAY. BURKE

&&

.AVIATION...A WEAK UPPER LEVEL DISTURBANCE OVER THE PAC NW WILL
MAINTAIN A CHANCE OF SHOWERS ACROSS WESTERN WA TODAY. THE FLOW ALOFT
IS W/NW WITH ONSHORE FLOW AT THE SURFACE. THERE IS A MIX OF CLOUDS
OVER THE REGION BUT GENERALLY VFR. A WARM FRONT WILL BRING RAIN TO
THE AREA ON THURSDAY...WITH MODERATE TO HEAVY RAIN POSSIBLE ON THE
COAST. 33

KSEA...ISOLATED SHOWERS IN THE VICINITY TODAY WITH VFR CONDITIONS
EXPECTED. SURFACE WINDS WILL REMAIN SOUTHERLY TO 10 KT. 33

&&

.MARINE...POST-FRONTAL ONSHORE FLOW ACROSS WESTERN WA WILL EASE THIS
AFTERNOON. WESTERLY GALES WILL CONTINUE THROUGH THE STRAIT OF JUAN
DE FUCA THIS MORNING. A STRONG WARM FRONT WILL ARRIVE ON THURSDAY
WITH GALES FORECAST OVER MANY ZONES. A STRONG COLD FRONT WILL FOLLOW
ON FRIDAY. ONSHORE FLOW WILL CONTINUE THIS WEEKEND. ANOTHER VIGOROUS
PACIFIC FRONTAL SYSTEM MAY ARRIVE EARLY NEXT WEEK.

A LARGE WESTERLY SWELL TRAIN OF 15 TO 18 FEET WILL REACH THE
WASHINGTON COASTAL WATERS THURSDAY NIGHT. THE SWELLS WILL
PEAK FRIDAY NIGHT AS HIGH AS 22 FEET BEFORE SUBSIDING ON SATURDAY.
COASTAL AND OTHER MARITIME INTERESTS SENSITIVE TO LARGE SWELL
REACHING THE COAST SHOULD MONITOR FORECASTS CLOSELY THIS WEEK. THIS
INCLUDES THE OCEAN SHORES COMMUNITY WHERE BEACH EROSION IS
ESPECIALLY PROBLEMATIC. A HIGH SURF ADVISORY HAS BEEN ISSUED. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WINTER WEATHER ADVISORY CASCADES UNTIL 10 AM.
     HIGH SURF ADVISORY CENTRAL COAST.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT.
     SMALL CRAFT ADVISORY COAST...WEST ENTRANCE STRAIT AND NORTHERN
     INLAND WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML