Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 090428
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
828 PM PST MON FEB 8 2016

.SYNOPSIS...A STRONG UPPER LEVEL RIDGE AND LOW LEVEL OFFSHORE FLOW
WILL BRING ONE MORE SUNNY AND MILD DAY TO WESTERN WASHINGTON ON
TUESDAY. SOUTHWEST FLOW ALOFT WILL DEVELOP TUESDAY AS THE RIDGE
MOVES EAST...ALLOWING EMBEDDED WEAK SYSTEMS TO BRING MORE CLOUDS AND
SOME RAIN AT TIMES FROM TUESDAY NIGHT THROUGH THE REMAINDER OF THIS
WEEK.

&&

.SHORT TERM...THE STRONG UPPER RIDGE OVER W WA THIS EVENING COMBINED
WITH LOW LEVEL OFFSHORE FLOW WILL BRING ONE MORE SUNNY AND MILD DAY
TO W WA ON TUESDAY. SKIES WILL BE CLEAR ONCE AGAIN TONIGHT BUT AFTER
HIGHS IN THE MID 50S TO MID 60S TODAY...TUESDAY MORNING LOWS SHOULD
BE A LITTLE WARMER...IN THE MID 30S TO MID 40S. PATCHY FOG IS LIKELY
ONCE AGAIN TUESDAY MORNING...MAINLY OVER THE SW INTERIOR AND S PUGET
SOUND.

THE UPPER LEVEL RIDGE WILL CONTINUE DRIFTING SLOWLY E THROUGH
TUESDAY...REACHING THE ID BORDER 00Z/4 PM TUESDAY AFTERNOON. THE
DEPARTING RIDGE WILL ALLOW SW FLOW ALOFT TO DEVELOP OVER W WA WHICH
WILL ALLOW WEAK WEATHER SYSTEMS EMBEDDED IN THE SW FLOW TO REACH THE
AREA THE REST OF THE WEEK. THE FIRST WEAK UPPER LEVEL SHORTWAVE
TROUGH SHOULD REACH THE COAST AROUND 12Z/4 AM WEDNESDAY MORNING. THE
GFS AND NAM HAVE BEEN CONSISTENT IN SHOWING A LITTLE LIGHT RAIN FROM
THIS TROUGH...MAINLY OVER THE COAST. THE ECMWF AND CANADIAN HAVE
BEEN EQUALLY CONSISTENT KEEPING THIS FIRST SHORTWAVE DRY. THE
FORECAST COMPROMISES BETWEEN THE TWO SOLUTIONS WITH LOW CHANCE POPS
OVER THE AREA. THE MODELS ARE MORE IN AGREEMENT THAT ONE OR MORE
SMALL TRAILING SHORTWAVE TROUGHS WILL RESULT IN A BETTER CHANCE OF
RAIN WEDNESDAY NIGHT. THURSDAY COULD BE WETTER STILL WITH A WARM
FRONT REACHING THE AREA. THE GFS AND ECMWF HAVE THE WARM FRONT
BRUSHING THE AREA THURSDAY AS IT HEADS TOWARD VANCOUVER ISLAND.
THE WETTER CANADIAN MODEL BRINGS IT INLAND RIGHT OVER W WA. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 245 PM AFD...MODELS
GENERALLY HAVE A WET LOOKING SYSTEM MOVING THROUGH THE REGION
THURSDAY NIGHT THROUGH FRIDAY NIGHT AND THE FORECAST GENERALLY HAS
LIKELY POPS DURING THIS PERIOD. ANOTHER SYSTEM ARRIVES AROUND
SUNDAY. MODEL TIMING IS IMPRECISE BUT THE EXTENDED PERIOD DEFINITELY
LOOKS LIKE IT HAS MORE NORMAL WEATHER WITH CLOUDS AND RAIN. HIGHS
WILL BE MAINLY IN THE 50S. EXCEPT FOR A BRIEF PERIOD OVER THE
WEEKEND...THE SNOW LEVEL IN THE MOUNTAINS WILL BE 7000 FEET OR
HIGHER. BURKE

&&

.HYDROLOGY...RIVER FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS.

&&

.AVIATION...LIGHT FLOW ALOFT WILL BECOME SOUTHERLY AND INCREASE ON
TUESDAY AS AN UPPER RIDGE OVER THE AREA SHIFTS EAST. HIGH PRESSURE
INLAND WITH LOW PRESSURE OFFSHORE WILL CONTINUE TO GIVE OFFSHORE
FLOW.
THE AIR MASS IS DRY AND STABLE. THERE WILL BE PATCHY SHALLOW FOG IN
A FEW SPOTS BY DAYBREAK TUE...PROBABLY AT OLYMPIA AND IN A FEW RIVER
VALLEYS.

KSEA...NE BREEZE...CLEAR SKIES.

&&

.MARINE...OFFSHORE FLOW THROUGH TUESDAY. A WEAK WARM FRONT WILL BRUSH
THE AREA WED. ANOTHER FRONTAL SYSTEM WILL STALL JUST OFFSHORE THU AND
FRI...MOVING INLAND SAT. THE FRONTAL SYSTEMS WILL AFFECT MAINLY THE COAST
WITH SMALL CRAFT ADVISORY CONDITIONS THERE AT TIMES.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 AM PST TUESDAY
     FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO
     60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE
     10 TO 60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT
     GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO
     CAPE SHOALWATER 10 TO 60 NM-COASTAL WATERS FROM POINT
     GRENVILLE TO CAPE SHOALWATER OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 3 AM PST TUESDAY FOR
     GRAYS HARBOR BAR.

     SMALL CRAFT ADVISORY UNTIL 10 AM PST TUESDAY FOR COASTAL WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-WEST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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