High Wind in Washington, October 14, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
345 AM PDT SAT OCT 13 2012

.SYNOPSIS...A WARM FRONT WILL BRING RAIN TO THE NORTHERN PORTION OF
THE AREA THIS MORNING. A COLD FRONT WILL MOVE THROUGH THIS AFTERNOON
AND EVENING FOR MORE WIDESPREAD RAIN AND LOCALLY WINDY CONDITIONS.
ANOTHER VIGOROUS FRONT WILL MOVE THROUGH MONDAY AND MONDAY NIGHT.
SHOWERS WILL DIMINISH ON TUESDAY AND DRY WEATHER IS LIKELY WEDNESDAY
AND THURSDAY.

&&

.SHORT TERM...DOPPLER RADAR SHOWS WARM FRONT WELL THIS MORNING WITH
RAIN OVER MOSTLY THE NORTHERN PORTION OF THE AREA. HEAVIEST RAIN IS
IN THE NORTH CASCADES. SATELLITE IMAGERY SHOWS THE THE PARENT 968 MB
LOW IN THE GULF OF ALASKA WITH THE TRAILING COLD FRONT EXTENDING
FROM HAIDA GWAII TO JUST NORTH OF VANCOUVER ISLAND BACK OUT TO NEAR
40N/140W. AMSU IMAGERY CONTINUES TO INDICATE THE FRONT TAPPING INTO
SOME VERY MOIST AIR WITH TPW VALUES IN THE CORE STILL ABOVE 2
INCHES. COLD FRONT DROPPING DOWN THROUGH WESTERN WASHINGTON LATER
TODAY INTO TONIGHT. CURRENT TIMING PUTS THE FRONT ALONG A LINE FROM
ABOUT KBLI-KUIL AT 00Z...MOUNT BAKER TO KSEA TO KAST AT 03Z AND
SOUTH AND EAST OF THE CWA BY MIDNIGHT. RAINFALL RATES WILL INCREASE
3 TO 6 HOURS AHEAD OF THE FRONT. WINDY CONDITIONS ARE ALREADY
OCCURING OVER THE NORTHERN PORTION OF THE AREA IN THE VICINITY OF
THE WARM FRONT. AS THE COLD FRONT MOVES SOUTH THROUGH THE AREA WINDS
WILL PICK UP OVER THE REST OF THE CWA.

PRECIPITATION AMOUNTS THROUGH TONIGHT WITH THE COMBINATION OF THE
WARM FRONT AND COLD FRONT WILL BE HIGHEST OVER THE NORTH CASCADES
AND OLYMPICS WITH ANOTHER 2 TO AROUND 3 INCHES EXPECTED. LESSER
AMOUNTS ARE FORECASTED FOR THE LOWLANDS WITH 1 TO 2 INCHES ALONG THE
COAST AND 0.25 TO 1 INCH FOR THE INTERIOR. THE SNOW LEVEL WILL BE
AROUND 9000 FT THROUGH TONIGHT.

PRECIPITATION WILL DECREASE BEHIND THE COLD FRONT LATER TONIGHT INTO
EARLY MONDAY MORNING BUT WITH A 140 KNOT JET OFF THE WASHINGTON
COAST THE BREAK IN THE PRECIPITATION WILL NOT BE LONG. ANOTHER
STRONG FRONTAL SYSTEM WILL APPROACH THE AREA ON MONDAY WITH RAIN
BEGINNING ALONG THE NORTH COAST EARLY IN THE DAY. THE RAIN WILL
SPREAD OVER THE ENTIRE AREA BY EARLY AFTERNOON. EARLIER MODEL RUNS
HAD HINTED AT THE POSSIBILITY OF STRONG WINDS ASSOCIATED WITH THIS
FRONT BUT THE 00Z RUNS HAVE THE PARENT LOW WELL TO THE NORTH OVER
HAIDA GWAII. STILL WITH THE 140 KNOT JET IN THE VICINITY AND THE LOW
CENTER PROGGED TO BE IN THE MID TO UPPER 970S MB...WE SHOULD SEE
WINDY CONDITIONS ALONG THE COAST AND IN THE NORTHWEST INTERIOR. THE
COLD FRONT WILL MOVE THROUGH WESTERN WASHINGTON MONDAY NIGHT.

AN UPPER TROUGH WILL FOLLOW THE FRONT INTO WESTERN WASHINGTON ON
TUESDAY KEEPING SHOWERS IN THE FORECAST. GOOD CONVERGENCE ZONE
PATTERN SETTING UP AND WITH THE FLOW ALOFT WEST NORTHWESTERLY EXPECT
THE CONVERGENCE ZONE TO GET INTO THE SEATTLE AREA DURING THE DAY.
BEHIND THE COLD FRONT THE AIR MASS WILL COOL OFF WITH SNOW LEVELS IN
THE MOUNTAINS DROPPING BELOW THE HIGHER PASS LEVELS...NEAR 4500
FEET. FELTON

.LONG TERM...EXTENDED MODELS REMAINING CONSISTENT WITH THEIR
SOLUTION FOR WEDNESDAY WITH A BREAK IN THE WET PATTERN WITH AN UPPER
LEVEL RIDGE OVER THE AREA AND SURFACE HIGH PRESSURE BUILDING IN. THE
MODEL SOLUTIONS DIVERGE ONCE AGAIN AFTER WEDNESDAY WITH THE SAME
STORY AS THE 00Z RUNS YESTERDAY. THE GFS BRINGS ANOTHER SYSTEM INTO
THE AREA THURSDAY NIGHT WHILE THE ECMWF IS A LITTLE SLOWER WITH THIS
SYSTEM HOLDING IT OFF UNTIL FRIDAY MORNING. CURRENT FORECAST IS MORE
IN LINE WITH THE GFS SOLUTION AND GIVEN THAT BOTH MODELS ARE SHOWING
GOOD RUN TO RUN CONSISTENCY SEE NO REASON TO CHANGE THE FORECAST AT
THIS POINT. BOTH THE GFS AND THE ECMWF KEEP A COOL TROUGH OVER
WESTERN WASHINGTON FOR NEXT WEEKEND KEEPING THE THREAT OF SHOWERS IN
THE FORECAST. FELTON

&&

.HYDROLOGY...ANOTHER BAND OF HEAVY RAIN ASSOCIATED WITH THE MAIN
BAROCLINIC BAND AND COLD FRONT WILL MOVE SOUTHEAST ACROSS THE AREA
THIS AFTERNOON INTO THE EVENING HOURS. BY THE END OF SUNDAY...THE
WEST SLOPES OF THE OLYMPICS AND THE NORTH CASCADES WILL SEE ANOTHER
2 TO AROUND 3 INCHES OF RAIN. THE INTERIOR LOWLANDS WILL RECEIVE
AMOUNTS OF AN INCH OR LESS WITH ONE TO TWO INCHES ALONG THE COAST.

SNOW LEVELS WILL RANGE FROM 8000 TO 9500 FEET THROUGH EARLY MONDAY
MORNING.

GIVEN THE EXCEPTIONALLY DRY ANTECEDENT CONDITIONS...THIS EPISODE IS
UNLIKELY TO PRODUCE ANY RIVER FLOODING. THE POSSIBLE EXCEPTION
IS THE UNIQUELY FLOOD-PRONE SKOKOMISH RIVER. HOWEVER...NORTHWEST
RIVER FORECAST CENTER GUIDANCE HAS CONSISTENTLY SHOWN THAT IT WILL
CREST ABOUT A FOOT BELOW FLOOD STAGE. IT CERTAINLY BEARS CONTINUED
WATCHING...BUT EVEN IF IT DOES FLOOD IT SHOULD BE MINOR.

THE PRECIPITATION EPISODE SHOULD RETURN HYDROLOGIC CONDITIONS TO
NORMAL FOR THIS TIME OF YEAR. MCDONNAL/FELTON

&&

.AVIATION...A STRONG FRONTAL SYSTEM WILL MOVE THROUGH WESTERN WA
TODAY. PERIODS OF RAIN WITH A FAIRLY LOW OVERCAST AND AREAS OF
REDUCED VISIBILITY IN THE RAIN WILL CONTINUE. THE RAIN HAS TAPERED
OFF OVER THE SOUTH HALF OF WESTERN WA EARLY THIS MORNING IN THE WARM
SECTOR SOUTH OF THE WARM FRONT...BUT THE RAIN WILL INCREASE AGAIN
LATER THIS MORNING. THE FRONTAL PASSAGE WILL PROBABLY REACH THE
COAST AROUND MID AFTERNOON AND MOVE THROUGH THE INTERIOR OF WESTERN
WA THIS EVENING. 19

KSEA...THERE WAS SOME IMPROVEMENT OVERNIGHT AS THE WARM FRONT
SHIFTED TO NW WA OR SRN BRITISH COLUMBIA BUT THEN LATER THIS MORNING
CEILINGS SHOULD FALL AGAIN WITH THE MAIN FRONT AND MORE RAIN THROUGH
THIS AFTERNOON. BREEZY SOUTHERLY WINDS EASING TONIGHT AFTER FROPA.

&&

.MARINE...GALE WARNING FOR THE COASTAL WATERS...ENTRANCES TO THE
STRAIT...AND FOR THE NORTHERN INLAND WATERS TODAY. WINDS WILL EASE
LATER THIS AFTERNOON OR EVENING AND THERE ISN'T LIKELY TO BE MUCH OF
A POSTFRONTAL WIND...NOT EVEN EXPECTING MUCH OF A WLY PUSH IN THE
STRAIT TONIGHT. THERE ARE SMALL CRAFT ADVISORIES ARE ON THE
REMAINDER OF THE WATERS AND THE FORECAST FOR PUGET SOUND AND
ADMIRALTY INLET IS SLY 20-30KT TODAY. ANOTHER SYSTEM MONDAY
AFTERNOON COULD PRODUCE GALES...ALTHOUGH THE 00Z ECMWF AND GFS ARE
PRETTY FAR APART IN THEIR SOLUTIONS...THE ECMWF HAS A MUCH DEEPER
LOW TRACKING ACROSS NRN VANCOUVER ISLAND MONDAY EVENING. BEHIND THAT
FRONT THERE WILL PROBABLY BE STRONG WESTERLY FLOW...GALE FORCE WLY
WINDS ARE LIKELY IN THE STRAIT MON NITE. 19

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING COASTAL WATERS...ENTRANCES TO THE STRAIT OF JUAN
DE FUCA...AND NORTHERN INLAND WATERS. SMALL CRAFT ADVISORIES
ELSEWHERE AND FOR THE GRAYS HARBOR BAR.

&&

WWW.WEATHER.GOV/SEATTLE

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