Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Graphics & Text | 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 43 44 45 46 47 48 49 50

000
FXUS66 KSEW 200406
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
906 PM PDT SUN OCT 19 2014

.SYNOPSIS...A SLOW MOVING FRONT WILL SPREAD RAIN ACROSS WESTERN
WASHINGTON TONIGHT AND MONDAY MORNING. THE TRAILING UPPER LEVEL
TROUGH WILL BRING SHOWERS TO THE AREA MONDAY AFTERNOON AND NIGHT. A
STRONGER AND MUCH WETTER FRONTAL SYSTEM WILL REACH THE AREA TUESDAY
AFTERNOON...WITH PERIODS OF RAIN CONTINUING INTO THURSDAY. UNSETTLED
WEATHER WILL CONTINUE INTO THE WEEKEND AS A LARGE UPPER LEVEL TROUGH
APPROACHES THE COAST.

&&

.SHORT TERM...THE FRONT ALONG THE COAST HAS BROUGHT RAIN TO AREAS
WEST OF PUGET SOUND THIS EVENING. RAIN WILL SPREAD ACROSS THE REST
OF THE INTERIOR TONIGHT AS THE FRONT SLOWLY DRAGS INLAND. RAIN HAS
BEEN FAIRLY HEAVY ALONG THE N COAST WITH OVER AN INCH SO FAR AT
QUILLAYUTE AND FORKS. AWAY FROM THE OLYMPICS WHERE TERRAIN IS
ENHANCING THE RAINFALL...AMOUNTS HAVE BEEN MUCH LESS. ACCORDING TO
THE SHORT RANGE HRRR GUIDANCE THE RAIN SHOULD DIMINISH OVER THE N
COAST BEFORE MIDNIGHT...BUT CONTINUE TO SOAK THE OLYMPICS ALL NIGHT.
RAIN SHOULD SPREAD ACROSS CENTRAL PUGET SOUND AROUND MIDNIGHT.

RAIN WILL CONTINUE OVER W WA THROUGH MONDAY MORNING BEFORE THE FRONT
FINALLY WEAKENS OVER THE CASCADES. THE TRAILING UPPER LEVEL TROUGH
WAS CENTERED OFFSHORE ALONG 135W AT 03Z/8 PM. THE AIR MASS UNDER THE
TROUGH LOOKS NICELY UNSTABLE ON IR SATELLITE IMAGERY WITH ISOLATED
LIGHTING STRIKES SHOWING UP OFFSHORE ALONG ROUGHLY 130W. THE TROUGH
AXIS WILL MOVE OVER THE OFFSHORE WATERS MONDAY AFTERNOON WITH THE
UNSTABLE AIR MASS REACHING THE COASTAL WATERS IN THE MORNING AND
PROBABLY THE IMMEDIATE COAST AND PART WAY INLAND MONDAY AFTERNOON.
GFS LIFTED INDICES GET DOWN TO ABOUT -2 OVER THE COASTAL WATERS
MONDAY AFTERNOON WHILE THE NAM HQM SOUNDING HAS -3 AND CAPE AROUND
700 J/KG. I WILL ADD A SLIGHT CHANCE OF THUNDERSTORMS TO THE COAST
AND COASTAL WATERS FOR MONDAY.

MODELS SOLUTIONS FOR TUESDAY AND WEDNESDAY CONTINUE TO EVOLVE WITH
RESPECT TO THE DETAILS. THE SCREAMING MESSAGE REMAINS THE
SAME...VERY WET WITH POTENTIAL HEAVY RAINFALL OVER THE OLYMPICS.
GFS/ECMWF/NAM ALL SHOW A WEAK FRONT EMERGING OUT OF THE SYSTEM
CURRENTLY FAR OFFSHORE ALONG 160W. THIS FRONT REACHES 130W AROUND
12Z/5 AM TUESDAY. EARLIER MODELS SOLUTIONS SHOWED THIS FRONT
REACHING THE COAST TUESDAY...BUT THE LATEST CONSENSUS SOLUTION IS
FOR A STRONG WAVE...DRIVEN ACROSS THE NE PACIFIC BY A 140KT JET
STREAK...TO OVERTAKE THE FRONT OVER THE OFFSHORE WATERS TUESDAY
AFTERNOON. A STRONG WARM FRONT INTENSIFYING JUST OFFSHORE WILL MOVE
INLAND TUESDAY EVENING. VERY WINDY CONDITIONS SHOULD DEVELOP OVER
THE COAST AND N INTERIOR TUESDAY NIGHT AND HEAVY RAIN SHOULD DRENCH
THE COAST AND OLYMPICS. 850 MB WINDS S-SW 60 KT SHOULD AID
OROGRAPHIC PRECIP OVER THE OLYMPICS. SNOW LEVELS WILL BE HIGH. RAIN
WILL SPREAD OVER INTERIOR AREAS OVERNIGHT...WITH THE CORE OF THE
PRECIP SHIFTING OVER THE CASCADES AND WEAKENING ON WEDNESDAY. HEAVY
RAIN SHOULD BE LIMITED TO TUESDAY NIGHT AND WEDNESDAY...WITH A 4-5
INCH BULLSEYE OVER THE OLYMPICS AND UP TO AN INCH OVER THE LOWLANDS.

MODELS ARE SHOWING PERIODS OF RAIN CONTINUING IN THE MOIST SW FLOW
ON WEDNESDAY...BUT THE HEAVIEST PRECIP SHOULD BE OVER. OF COURSE
SINCE THE DETAILS HAVE BEEN A BIT OF A MOVING TARGET THE PAST COUPLE
OF DAYS...BE PREPARED FOR CHANGES. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 3 PM AFD...THE PATTERN
LOOKS MORE SHOWERY IN BOTH THE GFS AND EURO MODELS ON FRIDAY. MODELS
THEN DIVERGE WITH THE GFS STILL SHOWERY ON THE WEEKEND BUT THE EURO
BRINGING ANOTHER FRONT SATURDAY WITH SHOWERS ON SUNDAY. FOR NOW HAVE
STUCK WITH THE IDEA OF SHOWERS LIKELY ON FRIDAY WITH A CHANCE OF
SHOWERS ON SATURDAY AND SUNDAY. SHOWERS MAY BE MORE LIKELY ON THE
COAST. HEIGHTS DO FALL A BIT SO OVERNIGHT LOWS WILL BE LOWER...MAYBE
BELOW 50 DEGREES. BURKE

&&

.HYDROLOGY...3 PM DISCUSSION...THE SYSTEM TONIGHT AND MONDAY IS WET
BUT DOES NOT HAVE ENOUGH RAIN TO CAUSE FLOODING. THE OLYMPICS WILL
GET THE MOST RAIN WITH PERHAPS 2 INCHES. THIS WILL BE THE SECOND
RAINY EVENT OVER THE OLYMPICS IN THREE DAYS. YESTERDAY MORNING THE
SKOKOMISH RIVER REACHED 15.3 FEET AND IT IS LIKELY TO GET AROUND
THAT HIGH AGAIN ON MONDAY. FLOOD STAGE ON THE SKOKOMISH IS 16.5 FEET.

THE GFS AND WRF VERSION OF THE HEAVY RAIN BEGINNING TUESDAY NIGHT IS
PROBABLY ENOUGH TO BRING THE SKOKOMISH RIVER TO FLOOD STAGE. MODELS
CONFINE FLOOD-PRODUCING RAINFALL TO THE OLYMPIC PENINSULA AND
PROBABLY JUST TO THE SKOKOMISH RIVER BASIN. ANY FLOODING ON THE
SKOKOMISH RIVER WOULD PROBABLY OCCUR WEDNESDAY NIGHT OR THURSDAY.

&&

.AVIATION...AN UPPER TROUGH OFFSHORE WILL MOVE OVER THE PAC NW
MONDAY. THE ASSOCIATED SURFACE FRONT WILL WEAKEN AND PUSH THROUGH
WRN WA LATER TONIGHT AND MONDAY MORNING. STRONG SLY FLOW
ALOFT...BECOMING LIGHT TO MODERATE SW FLOW BEHIND THE FRONT. MOIST
AND STABLE CONDITIONS...BECOMING UNSTABLE ON MONDAY. RAIN TONIGHT
WILL TRANSITION TO SHOWERS MONDAY MORNING WITH ISOLATED
THUNDERSTORMS POSSIBLE NEAR THE COAST.

KSEA...MID OR HIGH CLOUDS. CEILINGS LOWERING LATER TONIGHT WITH RAIN
DEVELOPING MONDAY MORNING. THERE SHOULD BE SOME IMPROVEMENT LATER
MONDAY AS RAIN CHANGES TO SHOWERS. SOUTH WIND 5 TO 10 KNOTS. DTM

&&

.MARINE...A FRONT ALONG THE COAST WILL SLOWLY SHIFT INTO THE INLAND
WATERS MONDAY MORNING AND DISSIPATE. SMALL CRAFT SLY WINDS WILL
CONTINUE TONIGHT OVER THE COASTAL WATERS AND INLAND WATERS N OF
PUGET SOUND. WINDS EASING BELOW 20 KT THROUGHOUT BY MONDAY MORNING.
10 TO 13 FOOT WEST SWELLS WILL LINGER OVER THE COASTAL WATERS
THROUGH MONDAY NIGHT. A SMALL CRAFT FOR HAZARDOUS SEAS IS UP FOR
SWELL OVER THE COAST AND W ENTRANCE MONDAY.

ADDITIONAL STRONG FRONTAL SYSTEMS WILL AFFECT THE WATERS LATER THIS
WEEK. FOR NOW IT LOOKS LIKE ONE SYSTEM WILL MOVE THROUGH THE AREA
AROUND TUESDAY NIGHT WITH ANOTHER ONE AROUND WEDNESDAY NIGHT. EACH
OF THESE SYSTEMS WILL BRING AT LEAST SMALL CRAFT ADVISORY WINDS TO
MOST OF THE WATERS. GALES ARE LIKELY FOR THE COASTAL WATERS AND
ENTRANCES TO THE STRAIT AS EACH FRONT MOVES THROUGH. SCHNEIDER/DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY ALL WATERS TONIGHT EXCEPT PUGET SOUND.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COAST AND WEST ENTRANCE
     MONDAY.


&&

$$

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.