Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42

000
FXUS66 KSEW 191025
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT SUN OCT 19 2014

.SYNOPSIS...AN UPPER RIDGE WILL GIVE DRY AND WARMER WEATHER SUNDAY
OVER THE INTERIOR WHILE THE NEXT FRONT APPROACHES THE COAST. THE
FRONT WILL BRING RAIN TO THE COAST LATE SUNDAY...AND TO THE INTERIOR
SUNDAY NIGHT AND MONDAY. THE ASSOCIATED UPPER LEVEL TROUGH WILL
FOLLOW MONDAY NIGHT...THEN ANOTHER FRONT WILL REACH THE AREA
TUESDAY. MOIST SOUTHWEST FLOW ALOFT WILL CONTINUE THE REST OF NEXT
WEEK.

&&

.SHORT TERM...WESTERN WA IS IN THE WARM SECTOR WHICH LEAD TO PRETTY
MILD TEMPS OVERNIGHT...A FEW SPOTS ARE STILL IN THE LOWER 60S. THE
WARM FRONT IS OVER B.C. BUT THERE ARE A FEW SHOWERS DRIFTING OVER
THE NORTH COAST. THE MAIN COLD FRONT WILL STALL OFFSHORE
TODAY...BECOMING NORTH-SOUTH ORIENTATED...THEN SLOWLY SHIFT INLAND
TONIGHT. MODELS SHOW RAIN HOLDING OFF IN THE INTERIOR UNTIL LATE
TONIGHT OR EARLY MON MORNING. THAT BEING SAID...MON MORNING LOOKS
RATHER WET FOR THE INTERIOR AS THE FRONT DRAGS THROUGH. A COOL UPPER
LEVEL TROUGH WILL NUDGE INLAND MON AFTERNOON AND COULD SEE A FEW
THUNDERSTORMS ALONG THE COAST AND SOUTH PART OF THE CWA.

THE AIR MASS WILL REMAIN COOL...MOIST AND UNSTABLE ON TUE AS AN
UPPER LEVEL TROUGH REMAINS OVER THE PAC NW. EXPECT MORE RAIN TUE
EVENING AS ANOTHER WARM FRONT MOVES INLAND.

AN UPPER LEVEL LOW OVER THE GULF OF AK WILL STEER MOIST SW FLOW INTO
WESTERN WA ON WED FOR ANOTHER WET PERIOD OF WEATHER. MODELS SHOW UP
TO 2 INCHES OF RAIN ALONG THE COAST...WITH UP TO 4 INCHES IN THE
OLYMPICS. THIS PLUME OF MOISTURE WILL SHIFT SOUTH AND EAST WED NIGHT
INTO THU...WITH THE FOCUS FOR HEAVIER PRECIP /1-2 INCHES/ SHIFTING
TOWARD THE CENTRAL AND SOUTH CASCADES. THE INTERIOR MAY SEE AN INCH
OF RAIN OVER THIS PERIOD. 33

.LONG TERM...CONFIDENCE IN THE LONG TERM FORECAST REMAINS LOW AT
THIS POINT. BOTH THE GFS AND EURO DISAGREE ON THE STRENGTH OF A
RIDGE OVER THE WESTERN CONUS ON FRI. THE EURO MAINTAINS DRY WEATHER
WITH THE RIDGE...WHILE THE GFS BRINGS AN UPPER LOW INLAND FOR MORE
RAIN. AN UPPER LEVEL TROUGH MAY CROSS THE REGION FOR MORE SHOWERS
OVER THE WEEKEND...BUT THE EXACT TIMING IS OFF IN THE MODELS.
THEREFORE LITTLE CHANGES WERE MADE DURING THIS PERIOD AND WILL
MAINTAIN A FORECAST CLOSER TO CLIMO. 33

&&

.HYDROLOGY...THE SYSTEM TONIGHT AND MONDAY IS WET BUT DOES NOT
HAVE ENOUGH RAIN TO CAUSE FLOODING. THE SYSTEM LAST NIGHT BROUGHT AN
INCH PLUS TO THE OLYMPICS...AND THE NEXT ONE WILL BRING PERHAPS
ANOTHER 2 INCHES. THESE WILL SERVE TO PRIME THE PUMP...SO TO SPEAK.
PREVIOUSLY DRY AREAS WILL BECOME WET AND NEARLY EMPTY RIVERS ON THE
OLYMPIC PENINSULA WILL RISE TO WET SEASON LEVELS.

THE GFS AND WRF VERSION OF THE HEAVY RAIN BEGINNING TUESDAY NIGHT IS
PROBABLY ENOUGH TO BRING THE SKOKOMISH RIVER TO FLOOD STAGE. IF THE
OUTLIER EURO SOLUTION IS CORRECT THEN SOME MORE RIVERS ON THE
OLYMPIC PENINSULA SHOULD RISE SIGNIFICANTLY...PERHAPS TO FLOOD
STAGE. MODELS DO CONFINE FLOOD-PRODUCING RAINFALL TO THE OLYMPIC
PENINSULA. ANY FLOODING ON THE SKOKOMISH RIVER WOULD PROBABLY OCCUR
WEDNESDAY NIGHT OR THURSDAY.

&&

.AVIATION...AN UPPER TROUGH WILL APPROACH THE PAC NW TODAY AS HIGH
PRESSURE SHIFTS EWD OVER THE ROCKIES. A SURFACE FRONT WILL MOVE ONTO
THE COAST THIS AFTERNOON AND PUSH ACROSS THE INTERIOR DURING THE
EVENING. STRONG S-SW FLOW ALOFT. AIR MASS SOMEWHAT UNSTABLE WITH
ISOLATED THUNDERSTORMS POSSIBLE ALONG THE FRONT. MAINLY MID/HIGH
CLOUDS THIS MORNING EXCEPT MOIST AT THE SURFACE RESULTING IN AREAS
OF FOG AROUND PUGET SOUND AND THE SW INTERIOR. FOG WILL BREAK UP AN
LIFT BY MID MORNING. RAIN DEVELOPING ALONG THE ENTIRE COAST BY
MIDDAY...THEN OVER THE INTERIOR DURING THE EVENING.

KSEA...FOG OVER THE S PUGET SOUND IS MIGRATING NWD AND WILL LIKELY
RESULT IN PERIODS OF IFR CIGS/VIS AT THE TERMINAL THROUGH MID
MORNING. INCREASING MID CLOUDS AND MIXING SHOULD BREAK UP THE FOG BY
16-17Z. RAIN WILL HOLD OFF UNTIL THE EVENING HOURS WITH VFR SKIES.
DTM

&&

.MARINE...A FRONT WILL ENTER THE COASTAL WATERS THIS AFTERNOON AND
PUSH THROUGH THE INTERIOR WATERS DURING THE EVENING. GALE FORCE
WINDS ARE EXPECTED OVER THE COASTAL WATERS TODAY. SMALL CRAFT WINDS
WILL DEVELOP FROM ADMIRALTY INLET NWD. WINDS WILL EASE BELOW 20 KT
THROUGHOUT AFTER MIDNIGHT ONCE THE FRONT PASSES.

ANOTHER STRONG FRONT WILL MOVE THROUGH THE WATERS TUESDAY FOLLOWED
BY YET ANOTHER SYSTEM ON WEDNESDAY. EACH OF THESE SYSTEMS WILL BRING
AT LEAST SMALL CRAFT ADVISORY WINDS TO MOST OF THE WATERS. GALES ARE
LIKELY FOR THE COASTAL WATERS AS EACH FRONT MOVES THROUGH. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING COASTAL WATERS AND WEST ENTRANCE STRAIT OF
     JUAN DE FUCA.
     SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT...ADMIRALTY
     INLET...AND NORTHERN INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.