Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 111602
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
901 AM PDT THU SEP 11 2014

.SYNOPSIS...HIGH PRESSURE WILL MAINTAIN A DRY WEATHER PATTERN INTO
EARLY NEXT WEEK. LOW LEVEL OFFSHORE FLOW TODAY WILL BE STRONG ENOUGH
TO CAUSE BREEZY CONDITIONS IN THE CASCADE FOOTHILLS AND OTHER
EXPOSED LOCATIONS TODAY. ABUNDANT SUNSHINE WILL ACCOMPANY A VERY
GRADUAL WARMING TREND OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...HIGH PRES ALOFT COMBINED WITH LOW LEVEL OFFSHORE FLOW
WILL RESULT IN DRY AND STABLE WEATHER ACROSS WESTERN WA OVER THE
NEXT SEVERAL DAYS. AREAS SHELTERED FROM THE WIND SAW LOWS IN THE 30S
THIS MORNING...LIKE OLYMPIA...SHELTON AND ARLINGTON. ELSEWHERE EAST
WINDS KEPT TEMPS MOSTLY IN THE 50S OVERNIGHT. BUT WITH PLENTY OF
SUNSHINE TODAY WE SHOULD SEE TEMPS RISE A FEW DEGREES ABOVE
NORMAL...WITH HIGHS IN THE 70S TO LOW 80S THIS AFTERNOON. IT WILL BE
ANOTHER CHILLY NIGHT IN THE SW INTERIOR...HOOD CANAL AND WESTERN
SKAGIT WITH LOWS AGAIN IN THE MID TO UPPER 30S.

THERE IS LITTLE CHANGE IN THE FORECAST FRIDAY THROUGH THE WEEKEND.
AN UPPER LEVEL RIDGE WILL CONTINUE TO BRING DRY WEATHER TO THE PAC
NW. LOW LEVEL OFFSHORE FLOW WILL PREVAIL WITH A THERMALLY INDUCED
TROUGH OF LOW PRES ALONG THE COAST. SKIES WILL REMAIN CLEAR. TEMPS
WILL MODERATE A FEW DEGREES WITH HIGH TEMPS ABOVE NORMAL. 33

NOTE...THE STRONG SOLAR FLARE THAT OCCURRED YESTERDAY WILL INCREASE
THE CHANCES OF SEEING THE AURORA BOREALIS OVER WESTERN WASHINGTON
TOMORROW NIGHT INTO THE WEEKEND. FOR MORE INFORMATION GO TO
WWW.SWPC.NOAA.GOV

.LONG TERM...PREVIOUS DISCUSSION...EXTENDED MODELS IN GOOD AGREEMENT
WITH THE UPPER LEVEL RIDGE CONTINUING TO DRIFT EAST ON SUNDAY WITH
THE RIDGE AXIS STILL OFFSHORE AT 00Z MONDAY. LIGHT OFFSHORE FLOW
ALSO CONTINUING ON SUNDAY WITH THE TEMPERATURES ALOFT WARMING
ANOTHER COUPLE OF DEGREES C. THIS WILL RESULT IN SLIGHTLY WARMER MAX
TEMPERATURES ON SUNDAY. RIDGE AXIS MOVING OVERHEAD ON MONDAY WITH
THE THERMALLY INDUCED TROUGH MOVING INLAND. THIS WILL ALLOW AN
AFTERNOON SEABREEZE TO KICK UP ALONG THE COAST LOWERING THE MAX
TEMPERATURES BY 5 TO 10 DEGREES. LITTLE CHANGE IN THE MAX TEMPS ON
MONDAY FOR THE INTERIOR. PATTERN STARTS TO BREAK DOWN ON TUESDAY
WITH THE UPPER LEVEL RIDGE AXIS EAST OF THE AREA. THERMALLY INDUCED
TROUGH ALSO MOVING INTO EASTERN WASHINGTON BY THE 00Z WEDNESDAY.
TEMPERATURES ALOFT ARE STILL WARM OVER THE AREA WITH MODEL 850 MB
TEMPERATURES STILL PLUS 14 TO 17C. FOR NOW WILL GO WITH A VERY WEAK
PUSH SCENARIO WITH HIGHS ON TUESDAY UP TO 5 DEGREES COOLER FOR THE
INTERIOR. MODEL CONSENSUS BREAKS DOWN ON WEDNESDAY WITH THE ECMWF
AND CANADIAN KEEPING THE NEXT SYSTEM TO REACH THE AREA OFFSHORE
WHILE THE GFS HAS PRECIPITATION MOVING INTO WESTERN WASHINGTON IN
THE AFTERNOON AND OVER MOST OF THE AREA BY 06Z THURSDAY. CURRENT
FORECAST IS MORE IN LINE WITH THE GFS. IF THE MODEL TRENDS CONTINUE
LOOK FOR THE CHANCE OF SHOWERS TO BE TAKEN OUT OF THE WEDNESDAY
FORECAST. FELTON

&&

.FIRE WEATHER...A STRONG EAST WIND EVENT IS UNDERWAY THIS
MORNING...WITH CRITICAL COMBINATIONS OF WIND...LOW HUMIDITY AND DRY
FUELS EXPECTED TODAY FOR A LARGE PORTION OF WESTERN WASHINGTON. THE
STRONGEST WINDS TODAY ARE EXPECTED WEST OF THE MAJOR CASCADE PASSES
AND OVER THE NORTHWEST OLYMPIC PENINSULA. DRY GUSTY EAST AND
NORTHEAST WINDS ARE EXPECTED THIS AFTERNOON OVER THE PUGET SOUND
LOWLANDS AND THROUGH THE CHEHALIS GAP TO GRAYS HARBOR. WILL EASILY
VERIFY RED FLAG WIND AND HUMIDITY CRITERIA OVER A LARGE AREA TODAY.
IN FIRE WEATHER ZONE 659 (CENTRAL CASCADES)...FOCUS IS MOSTLY ON THE
SOUTHERN HALF OF THE ZONE (ENUMCLAW AND STAMPEDE PASS ON SOUTH) DUE
TO MOIST FUELS FURTHER NORTH ALONG THE I-90 CORRIDOR.

THE EAST WIND EVENT WILL PEAK IN STRENGTH TODAY...BUT EAST WINDS
WILL CONTINUE FRIDAY AND SATURDAY AT LESSER SPEEDS. EAST WINDS WILL
EASE FURTHER ON SUNDAY AND MONDAY...BUT THE AIR MASS WILL CONTINUE
TO BE WARM AND DRY THROUGH TUESDAY. POOR NIGHTTIME HUMIDITY RECOVERY
WILL CONTINUE...AND MID-LEVEL HAINES 5-6 CONDITIONS ON SUNDAY AND
MONDAY. THOSE NUMBERS HIGHLIGHT A VERY DRY AND SOMEWHAT UNSTABLE AIR
MASS IN THE 850-700 MB LAYER...WHICH WILL SUPPORT AN ACTIVE BURNING
ENVIRONMENT IF ANY FIRES GET STARTED IN THE NEXT FEW DAYS.  HANER

&&

.AVIATION...AN UPPER LEVEL RIDGE CENTERED AROUND 135W WILL GIVE DRY
NW FLOW ALOFT TO THE AREA THROUGH FRIDAY. THE AIR MASS IS STABLE. AT
THE SURFACE...A THERMALLY INDUCED TROUGH OF LOW PRESSURE EXTENDS
FROM THE WEST COAST OF VANCOUVER ISLAND SOUTHWARD THROUGH THE
WASHINGTON AND OREGON COASTAL WATERS WHILE A STRONG RIDGE OF HIGH
PRESSURE EXTENDS FROM SOUTH CENTRAL BRITISH COLUMBIA INTO THE
NORTHERN GREAT PLAINS. THE RIDGE TO THE NORTHEAST OF THE AREA WILL
SLOWLY WEAKEN THROUGH FRIDAY ALLOWING OFFSHORE FLOW TO WEAKEN
SOMEWHAT.

EXPECT GOOD VFR CONDITIONS WITH ONLY A FEW CIRRUS CLOUDS PASSING THE
AREA AT TIMES THROUGH FRIDAY. ALBRECHT

KSEA...EXPECT NEARLY CLEAR SKIES WITH ONLY A FEW PASSING CIRRUS
CLOUDS THROUGH FRIDAY. EAST TO NORTHEAST WINDS 10-15 KT WILL TURN
NLY AROUND 20Z THEN WILL VEER TO NELY AROUND 04Z. ALBRECHT

&&

.MARINE...A THERMALLY INDUCED TROUGH OF LOW PRESSURE EXTENDS FROM
THE WEST COAST OF VANCOUVER ISLAND SOUTHWARD THROUGH THE WASHINGTON
AND OREGON COASTAL WATERS WHILE A STRONG RIDGE OF HIGH PRESSURE
EXTENDS FROM SOUTH CENTRAL BRITISH COLUMBIA INTO THE NORTHERN GREAT
PLAINS. THE RIDGE TO THE NORTHEAST OF THE AREA WILL SLOWLY WEAKEN
THIS AFTERNOON THROUGH FRIDAY ALLOWING OFFSHORE FLOW TO WEAKEN
SOMEWHAT.

SMALL CRAFT ADVISORY CONDITIONS ALONG THE WEST ENTRANCE OF THE
STRAIT OF JUAN DE FUCA...AND THE ADJACENT NEAR COASTAL ZONE FROM
CAPE FLATTERY TO JAMES ISLAND AND OUT 10 NM...WILL SUBSIDE DURING
THE AFTERNOON HOURS. NORTH WINDS MAY REACH 20 KT AT TIMES OVER THE
OUTER COASTAL WATERS AND OVER PUGET SOUND AND HOOD CANAL THIS
AFTERNOON AND EARLY THIS EVENING.

THE OFFSHORE FLOW PATTERN WILL WEAKEN SOMEWHAT FRIDAY THROUGH MONDAY
RESULTING IN LIGHTER WINDS. ALBRECHT

&&

SEW WATCHES/WARNINGS/ADVISORIES...
WA...RED FLAG WARNING FOR WIND AND LOW HUMIDITY THROUGH FRIDAY IN
     FIRE WEATHER ZONES 649...650...651...654...655...657...659
     (SOUTH HALF) AND 661.

PZ...SMALL CRAFT ADVISORY WEST ENTRANCE TO THE STRAIT OF JUAN DE
     FUCA...AND NORTHERN INNER COASTAL WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE/

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





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