Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 211644
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
944 AM PDT TUE OCT 21 2014

.SYNOPSIS...EXPECT A VERY WET AND OCCASIONALLY WINDY WEEK AHEAD AS
AN ACTIVE FALL WEATHER PATTERN DOMINATES SOUTHWEST WASHINGTON AND
NORTHWEST OREGON. THE SYSTEM WHICH BROUGHT SHOWERS AND A COUPLE
CLAPS OF THUNDER MONDAY HAS MOVED INTO EASTERN OREGON AND THE GREAT
BASIN. ENOUGH MOISTURE AND INSTABILITY REMAINS LEFT BEHIND FOR
SCATTERED SHOWERS THIS MORNING. MEANWHILE A STRONG FRONTAL SYSTEM IS
TAKING SHAPE OFFSHORE. THIS SYSTEM WILL BE A SLOW MOVER...SPREADING
LOCALLY HEAVY RAIN SOUTH AND EAST ACROSS THE FORECAST AREA TONIGHT
THROUGH EARLY THURSDAY. THIS FRONT WILL PRODUCE STRONG COASTAL WINDS
AS WAVES OF LOW PRESSURE DEVELOP ALONG IT AND PASS BY. ANOTHER WET
AND POTENTIALLY WINDY FRONT IS EXPECTED BY THE WEEKEND.

&&

.UPDATE...MODELS HAVE CHANGED LITTLE THUS FAR WITH THE 12Z OUTPUT.
THE WARM FRONT IS CURRENTLY SPREADING ACROSS THE AREA WITH THE
TRAILING COLD FRONT STILL WELL OFFSHORE. THE OCCLUSION IS SITUATED
JUST OFFSHORE THE NORTH TIP OF VANCOUVER ISLAND. THIS SETUP PLACES
OUR REGION SQUARELY IN THE WARMING SECTOR OF THE FRONTAL SYSTEM.
CONDITIONS ARE STILL VERY FAVORABLE TO SEE A COASTAL JET DEVELOP
WITH NAM12 AND RAP INDICATED PEAK SPEEDS AROUND 67 MPH CENTERED
AROUND 900 MB. THUS FEEL MOST GUSTS ALONG THE COAST WILL PEAK OUT
AROUND 60 MPH GIVEN BROAD ISENTROPIC LIFT AHEAD OF THE COLD FRONT
AND WINDS AT THAT LEVEL VEERING MORE SW THAN THE SOUTH WINDS TRAPPED
ALONG THE TERRAIN. WILL STILL CARRY THE HIGHER SPEEDS TONIGHT IN THE
PRODUCTS FOR NOW AS THE EXPOSED HIGHER HEADLANDS SUCH AS CAPE
FOULWEATHER...CAPE LOOKOUT...AND CAPE DISAPPOINTMENT CERTAINLY COULD
FULLY REALIZE THOSE HIGHER SPEEDS. RAIN AMOUNTS REMAIN ON TRACK AS
EXPECTED FROM OVER THE LAST COUPLE DAYS. /JBONK

&&

.PREV DISC... /ISSUED 351 AM PDT TUE OCT 21 2014/

SHORT TERM...TODAY THROUGH THURSDAY...THE MAIN FEATURE OF THE SHORT
TERM FORECAST PERIOD WILL BE OUR STRONGEST FRONTAL SYSTEM SO FAR
THIS SEASON...PRODUCING STRONG COASTAL WINDS LATER TODAY THROUGH
WEDNESDAY. THIS FRONT WILL ALSO HAVE A STRONG TAP TO SUBTROPICAL
MOISTURE...SPREADING LOCALLY HEAVY RAIN SOUTHWARD ACROSS SOUTHWEST
WASHINGTON AND NORTHWEST OREGON TONIGHT THROUGH THURSDAY MORNING.
CONDITIONS ARE RIPE FOR CYCLOGENESIS ALONG THE FRONT...AND MULTIPLE
WAVES OF LOW PRESSURE ARE EXPECTED TO DEVELOP AND RIDE NE ALONG THE
FRONT AS IT PASSES SLOWLY SOUTHWARD ACROSS WESTERN WA/OR.

FIRST THINGS FIRST...SCATTERED SHOWERS CONTINUE THIS MORNING IN THE
RESIDUAL MOISTURE AND CONDITIONAL INSTABILITY LEFT BEHIND THE FRONT
WHICH MOVED THROUGH THE FORECAST AREA MONDAY. THESE SHOULD GRADUALLY
TAPER OFF THIS MORNING AS THE AIR MASS WARMS ALOFT...HOWEVER THE WARM
ADVECTION ALOFT WILL ALSO PRODUCE ISENTROPIC LIFT. THIS SHOULD RESULT
IN RAINY DAY FOR THE COAST AND PERHAPS OUR NORTHERN ZONES AS A WARM
FRONT LIFTS THROUGH NW OREGON AND SW WASHINGTON.

BEHIND THE WARM FRONT...THE DOOR WILL BE OPENED FOR A STRENGTHENING
COASTAL JET AHEAD OF AN APPROACHING COLD FRONT. THOUGH DETAILS
VARY...MODEL RUNS HAVE BEEN FAIRLY CONSISTENT IN SUGGESTING A 55 TO
65 KT SOUTHERLY JET DEVELOPING ALONG THE COAST AT 950 MB. THIS SHOULD
BE AMPLE FOR 55-70 MPH GUSTS AT TIMES ALONG THE BEACHES AND HEADLANDS
FROM THE S WA COAST DOWN TO THE LINCOLN AND POSSIBLY LANE COUNTY
COAST. THEREFORE WILL BE UPGRADING THE HIGH WIND WATCH TO A WARNING
FOR THESE AREAS. TIMING WILL REMAIN THE SAME FOR THE S WA/N OR
COAST...THIS AFTERNOON INTO WEDNESDAY MORNING. WILL EXTEND THE TIMING
FOR THE CENTRAL COAST INTO MIDDAY WEDNESDAY TO GIVE THE FRONT SOME
TIME TO PUSH SOUTH OF THE LANE/DOUGLAS COUNTY BORDER.

AS MENTIONED ABOVE...MULTIPLE WAVES OF LOW PRESSURE ARE EXPECTED TO
DEVELOP ALONG THE FRONT...WHICH WILL SLOW DOWN ITS SOUTHWARD
PROGRESS. THESE WAVES OF LOW PRESSURE WILL LIKELY EACH PRODUCE A
BURST OF COASTAL WIND TO ITS SOUTH AND EAST ALONG THE FRONT. SO WINDS
MAY BE STRONG FOR A FEW HOURS...LET UP A BIT...THEN PICK BACK UP
AGAIN UNTIL THE FRONT PUSHES SOUTH OF COASTAL LOCATIONS. THERE IS
STILL A GOOD DEAL OF UNCERTAINTY AS TO HOW DEEP THESE LOWS WILL
GET...WHICH OF COURSE WOULD IMPACT THE EXPECTED WIND SPEEDS.

THE 06Z NAM IS DEVELOPING A 990 MB LOW ALONG THE FRONT BY 09Z WED...
PUSHING IT INTO VANCOUVER ISLAND WED MORNING. THE FIRST SIGNS OF THIS
DEVELOPING LOW ARE ALREADY SHOWING UP ON INFRARED/WATER VAPOR IMAGERY
WITH A BAROCLINIC LEAF TAKING SHAPE ALONG THE FRONT NEAR 150W. A
SECONDARY LOW WILL LIKELY DEVELOP ALONG THE TRIPLE POINT OF THE
RESULTING OCCLUDING FRONT OFF THE NORTHERN OREGON COAST...AND PERHAPS
A TERTIARY LOW THEREAFTER. THESE WAVES OF LOW PRESSURE WILL SLOW THE
SOUTHWARD PROGRESS...EACH PRODUCING A BURST OF COASTAL WIND TO ITS
SOUTH AND EAST ALONG THE FRONT. SO WINDS MAY BE STRONG FOR A FEW
HOURS...LET UP A BIT...THEN PICK BACK UP AGAIN UNTIL THE FRONT PUSHES
SOUTH OF COASTAL LOCATIONS. THERE IS STILL A GOOD DEAL OF UNCERTAINTY
AS TO HOW DEEP THESE LOWS WILL GET...WHICH OF COURSE WOULD IMPACT THE
EXPECTED WIND SPEEDS.

ALSO THE 06Z NAM IS BEGINNING TO SHOW SOME POTENTIAL FOR GUSTY WINDS
IN THE WILLAMETTE VALLEY...AS ITS SECONDARY LOW MOVES ONSHORE NEAR
ASTORIA WED MORNING. THIS TRACK COULD OPEN UP ENOUGH SOUTHERLY
GRADIENT FOR 30-40 MPH WIND GUSTS IN THE WILLAMETTE VALLEY AND
STRONGER WIND GUSTS IN THE COASTAL COMMUNITIES. FOR NOW IT APPEARS
WINDS WILL REMAIN SUB-ADVISORY CRITERIA INLAND...BUT WILL NEED TO
MONITOR CLOSELY.

NOT TO GET LOST IN ALL THE DISCUSSION ABOUT OUR FIRST COASTAL HIGH
WIND EVENT...IS THE POTENTIAL FOR RATHER IMPRESSIVE RAINFALL TOTALS
AS THIS SLOW MOVING...WAVY FRONT MOVES SLOWLY SOUTH ACROSS OUR
FORECAST AREA. THIS SYSTEM IS TAPPING INTO A DECENT ATMOSPHERIC RIVER
WHICH EXTENDS ALL THE WAY BACK BEYOND THE DATELINE. MADE ONLY MINOR
CHANGES TO THE QPF FORECAST...WITH 2 INCHES OF RAIN EXPECTED FOR THE
INLAND VALLEYS...2-4 INCHES ALONG THE COAST...AND 3-6 INCHES IN THE
HIGHER TERRAIN BY THURSDAY. IT WILL BE A CLOSE CALL WHETHER OR NOT
THIS WILL BE ENOUGH TO CAUSE PROBLEMS ON FLASHIER RIVERS LIKE THE
GRAYS RIVER IN THE WILLAPA HILLS...AS WELL AS THE BURN SCAR AREAS
FROM THE 36 PIT AND DECEPTION FIRES. IMPACTS ON THESE AREAS WILL NEED
TO BE MONITORED CLOSELY OVER THE COMING DAYS.

DUE TO THIS SYSTEMS SUBTROPICAL ORIGINS SNOW LEVELS WILL REMAIN
RATHER HIGH THROUGHOUT THIS EVENT...SO ONLY THE HIGHEST VOLCANO PEAKS
ABOVE 6000-7000 FEET WILL RECEIVE SIGNIFICANT SNOWFALL.

THE FRONT WILL FINALLY PUSH SOUTH AND EAST OF OUR FORECAST AREA
SOMETIME LATE WED NIGHT OR THU MORNING. SHOWERS WILL LINGER IN THE
COOL UNSETTLED AIR MASS BEHIND THE FRONT THURSDAY.  WEAGLE

LONG TERM...FRIDAY THROUGH MONDAY...MEDIUM RANGE GUIDANCE CONTINUES
TO STRUGGLE WITH HOW TO HANDLE THE LATE WEEK AND WEEKEND PERIOD.
THERE IS INCREASING AGREEMENT THAT ANOTHER POTENT LOW PRESSURE/
FRONTAL SYSTEM WILL DEVELOP OFFSHORE...PERHAPS BRINGING ANOTHER
PERIOD OF HEAVY RAIN AND GUSTY WINDS FRIDAY AND/OR SATURDAY. AS FOR
THE LONGWAVE PATTERN...THE LATEST 00Z RUNS ARE TRYING TO KEEP THE
MEAN RIDGE POSITION OVER THE WESTERN HALF OF THE UNITED STATES. THIS
IS NOT SURPRISING CONSIDERING THE LARGE POOL OF ABOVE NORMAL SEA
SURFACE TEMPS OVER THE NE PACIFIC. THE PACIFIC NORTHWEST MAY REMAIN
IN THE TRANSITION ZONE BETWEEN LONGWAVE RIDGING AND TROUGHING WELL
INTO NEXT WEEK...WHICH IS OF COURSE WHERE THE STORM TRACK TENDS TO
BE. THEREFORE ACTIVE AND WET WEATHER AT TIMES IS EXPECTED TO
CONTINUE INTO NEXT WEEK.  WEAGLE

&&

.AVIATION...SHOWERS CONTINUE THIS MORNING AS A WARM FRONT
APPROACHES THE REGION. EXPECT PRIMARILY VFR CONDITIONS TODAY AND
TONIGHT WITH BRIEF MVFR CIGS FORMING FROM TIME TO TIME. GUSTY
SOUTHERLY WINDS WILL PICK UP TODAY AND ESPECIALLY THIS EVENING.
COASTAL SITES MAY SEE WIND GUSTS TO 45 KT AT TIMES TONIGHT THROUGH
WED MORNING. A HIGH WIND WARNING IS NOW IN EFFECT FOR THE COASTAL
SITES. A COLD FRONT WILL SPREAD HEAVIER RAIN ONTO THE COAST
OVERNIGHT NIGHT AND INLAND TOMORROW MORNING.

KPDX AND APPROACHES...VFR PREVAILING THROUGH TONIGHT...ALTHOUGH A
BRIEF MVFR CIG MAY FORM THROUGH ABOUT 21Z IN SHOWERS. BREEZY
SOUTHERLY WINDS ARE EXPECTED THIS EVENING AND OVERNIGHT. A COLD
FRONT TO SPREAD STEADY RAIN IN AFTER 12Z TOMORROW. PYLE

&&

.MARINE...S/SW WINDS CONTINUE AROUND 10 TO 20 KT WITH GUSTS TO 25
KT THIS MORNING. WINDS WILL GRADUALLY INCREASE TODAY...REACHING
GALE FORCE BY MID AFTERNOON. THE STRONGEST WINDS ARE EXPECTED THIS
EVENING AND OVERNIGHT AHEAD OF AN APPROACHING COLD FRONT...WITH
GUSTS TO 40 TO 45 KT EXPECTED. SOME COASTAL JET ENHANCEMENT MAY
BRING A FEW 50 TO 55 KT GUSTS TO THE NEAR SHORE WATERS.

A WESTERLY SWELL ON THE ORDER OF 10 FT WILL CONTINUE FOR THE NEXT
FEW DAYS...BUT SEAS WILL INCREASE SIGNIFICANTLY TONIGHT AS THE
SOUTHERLY WINDS PICK UP. BASED ON THE LATEST MODEL GUIDANCE...SEAS
MAY APPROACH 20 KT LATER THIS EVENING AND OVERNIGHT.

WINDS AND SEAS ARE EXPECTED TO DROP OFF DURING THE DAY WEDNESDAY.
ADDITIONAL SYSTEMS ARE EXPECTED LATER THIS WEEK...BUT THE TONIGHT
INTO WEDNESDAY IS EXPECTED TO BE THE STRONGEST. PYLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO 9 AM PDT WEDNESDAY
     FOR NORTH OREGON COAST.

     HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO NOON PDT WEDNESDAY
     FOR CENTRAL OREGON COAST.

WA...HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO 9 AM PDT WEDNESDAY
     FOR SOUTH WASHINGTON COAST.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PDT THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO 11 AM PDT WEDNESDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PDT THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE
     OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM PDT
     WEDNESDAY.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.
&&



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