Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 282203
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
300 PM PDT SAT MAR 28 2015

.SYNOPSIS...SHOWERS REMAIN IN THE HIGHER TERRAIN OF THE CASCADES AND
COAST RANGE BUY WILL CONTINUE TO TAPER OFF AND EVENTUALLY END LATER
THIS AFTERNOON AND EARLY EVENING. A MOIST FRONTAL BOUNDARY WILL SIT
NEARLY STATIONARY OVER BRITISH COLUMBIA AND NORTHERN WASHINGTON THIS
WEEKEND...LEAVING US TO ENJOY MILD AND MOSTLY DRY WEATHER THROUGH MON
AS FLAT UPPER LEVEL RIDGING REMAINS OVER THE PAC NW. THE FRONTAL
BOUNDARY WILL SWING THROUGH AS A COLD FRONT MON NIGHT INTO
TUE...BRINGING WIDESPREAD RAIN AND SNOW LEVELS LOWERING DOWN TO THE
CASCADE PASSES. A FAIRLY PROGRESSIVE PATTERN THEN APPEARS TO BE ON
TAP FOR THE REST OF NEXT WEEK. EXPECT PLENTY OF CLOUDS...PERIODIC
ROUNDS OF SHOWERS...AND COOLER TEMPERATURES. SNOW LEVELS SHOULD
REMAIN BELOW THE CASCADE PASSES FOR MUCH OF NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH TUESDAY...
LIGHT SHOWERS CONTINUE IN THE COOL POST FRONTAL AIR MASS THIS
AFTERNOON...MAINLY OVER THE S WASHINGTON AND FAR N OREGON CASCADES
AND COAST RANGE. BASED ON RADAR IMAGERY...THE SHOWERS ARE BECOMING
NOTICEABLY LESS NUMEROUS AND LOWER TOPPED OVER THE PAST FEW HOURS AS
THE ATMOSPHERE BEGINS TO STABILIZE. EXPECT SHOWERS TO END COMPLETELY
BY EARLY THIS EVENING. OTHERWISE...EXPECT PARTLY CLOUDY SKIES WITH
PLENTY OF CUMULUS CLOUDS AROUND AND ALSO HIGH CIRRUS STREAMING IN
AHEAD OF A WARM FRONT.

AN OFFSHORE FRONTAL SYSTEM WILL REMAIN NEARLY STATIONARY OVER THE
WEEKEND...FOCUSING AN ATMOSPHERIC RIVER OF SUBTROPICAL MOISTURE ON
VANCOUVER ISLAND AND FAR NW WASHINGTON. THIS WILL LEAVE US TO ENJOY
MILD AND MAINLY DRY CONDITIONS ON THE WARM SIDE OF THE FRONT TONIGHT
THROUGH MOST OF MON. THE FCST MODELS CONTINUE TO INDICATE THAT THERE
IS A SLIGHT CHANCE THAT LIGHT RAIN MAY CLIP THE S WASHINGTON AND FAR
N OREGON COAST AT TIMES DURING THIS PERIOD. THERE WILL BE SOME HIGH
CLOUDS STREAMING ACROSS THE REGION ON SUN AND MON...ESPECIALLY FOR
THE NW PORTIONS OF THE FCST AREA. ELSEWHERE...EXPECT THERE TO BE SOME
DECENT SUNSHINE. AFTERNOON HIGH TEMPS SHOULD CLIMB BACK INTO THE MID
TO UPPER 60S OVER THE INTERIOR LOWLANDS.

AN UPPER LEVEL TROUGH WILL DIVE DOWN FROM THE GULF OF ALASKA ON
MON...FINALLY DRIVING THE STALLED FRONTAL BOUNDARY ONSHORE AS A COLD
FRONT. EXPECT RAIN TO PUSH ONTO THE COAST MON EVENING...THEN INLAND
OVERNIGHT. THE UPPER LEVEL TROUGH WILL MOVE THROUGH ON TUE...USHERING
IN A SIGNIFICANTLY COOLER AIR MASS. THE FCST MODELS ARE INDICATING
THAT THERE WILL BE PLENTY OF POSTFRONTAL SHOWERS ACROSS THE REGION ON
TUE. THE FCST MODEL SOUNDINGS ARE ALSO LOOKING DECENTLY UNSTABLE...SO
MAY NEED TO LOOK AT ADDING THUNDER CHANCES TO THE FCST IN THE NEXT
DAY OR TWO. AT THE VERY LEAST...IT WILL PROBABLY BE ONE OF THOSE DAYS
WITH PERIODIC HEAVY SHOWERS...SOME LIKELY CONTAINING SMALL HAIL. THE
COLDER AIR SHOULD ALSO DROP SNOW LEVELS DOWN TO THE CASCADE
PASSES...WHERE SEVERAL INCHES OF ACCUMULATING SNOW MAY FALL. PYLE


.LONG TERM...TUESDAY NIGHT THROUGH FRIDAY...A PROGRESSIVE PATTERN IS
EXPECTED FOR THE EXTENDED FCST PERIOD. BEHIND THE UPPER LEVEL TROUGH
ON TUE...FCST CONFIDENCE IS FAIRLY HIGH THAT ANOTHER SHORTWAVE WILL
MOVE ONSHORE WED...BRINGING CONTINUED SHOWERS AND MOUNTAIN SNOW INTO
THU MORNING. THERE IS THEN A SHORTWAVE UPPER LEVEL RIDGE THAT IS
MODELED TO MOVE INTO THE REGION ON THU. THIS MAY END UP PROVIDING A
BRIEF BREAK FROM THE SHOWER ACTIVITY LATER THU INTO FRI BEFORE A
DEEP UPPER TROUGH MOVES TOWARD THE COAST ON FRI INTO NEXT WEEKEND.
FCST CONFIDENCE BECOMES LOWER TOWARD THE END OF THE WEEK. FRI COULD
END UP BEING MOSTLY DRY...BUT THE FCST MODELS SEEM TO BE TRENDING
TOWARD SPEEDING UP THE ARRIVAL OF THE DEEP TROUGH...WHICH WOULD
BRING MORE RAIN ONSHORE FRI. PYLE

&&

.AVIATION...JUST A FEW SHOWERS REMAINING THIS AFTERNOON OVER SW
WASHINGTON AND ALSO IN THE CASCADES. VFR CONDITIONS AT THE
TERMINALS THIS AFTERNOON WITH VFR CIGS AND SCT CUMULUS WITH BASES
AROUND 3000 FT. MAY OCCASIONALLY SEE SOME MVFR CIGS DEVELOP WITH
THESE...BUT OTHERWISE VFR CONTINUES THIS EVENING WITH INCREASING
HIGH CLOUDS SPREADING OVER THE AREA. DEWPOINTS A BIT LOWER TODAY
THAN YESTERDAY AND OFFSHORE LOW LEVEL FLOW WILL EASE INTO THE
OVERNIGHT PERIOD ALONG WITH AT LEAST A BKN HIGH CLOUD DECK
OVERHEAD. THUS...THIS SHOULD PRECLUDE MOST FOG DEVELOPMENT. ONE
EXCEPTION MAY BE DOWN TOWARDS KEUG WHERE HIGH CLOUDS MAY NOT BE
AS THICK/PREVALENT...THOUGH EVEN THEN IT MAY BE A STRUGGLE TO
COOL ENOUGH FOR FOG DEVELOPMENT.

KPDX AND APPROACHES...VFR CIGS CONTINUE THIS AFTERNOON...BUT
SHOULD DECREASE AND SCATTER THIS EVENING. INCREASING HIGH CLOUDS
OVERNIGHT AND THESE SHOULD PRECLUDE FOG DEVELOPMENT. SOUTHERLY
SURFACE WINDS AROUND 10 KT WILL DECREASE LATER THIS EVENING AND
BECOME LIGHT/VARIABLE LATE. CULLEN

&&

.MARINE...SURFACE PRESSURE GRADIENT CONTINUES TO INCREASE A BIT IN
BETWEEN BUILDING HIGH PRESSURE OVER THE WATERS AND A LOW PRESSURE
SYSTEM IN THE GULF OF ALASKA. AN ASCAT PASS AROUND NOON TODAY
INDICATED WINDS OVER THE NORTHERN OUTER WATERS AROUND 18 KT NEAR
THE BOUNDARY OF THE OUTER WATERS. AS THE GRADIENT INCREASES A BIT
FURTHER...WINDS WILL INCREASE AND EXPECT SMALL CRAFT ADVISORY
STRENGTH GUSTS. THEREFORE HAVE ISSUED AN ADVISORY FOR WINDS FOR
THE NORTHERN OUTER WATERS WITH THE AREA OF CONCERN N OF CANNON
BEACH AND GENERALLY BEYOND 20 NM OFFSHORE. GUSTS TO 25 KT THROUGH
THE OVERNIGHT HOURS AND INTO EARLY SUN MORNING CAN BE EXPECTED.
ELSEWHERE...WINDS GENERALLY AROUND 15 KT OR LESS.

SEAS WILL HOLD AROUND 8 TO 9 FT TONIGHT...BEFORE POSSIBLY
INCREASING TO 10 FT LATE SUNDAY AFTERNOON INTO MONDAY. SOMEWHAT
LOWER CONFIDENCE IN THE EXTENT OF TIMING OF 10 FT SEAS SO HOLDING
OFF ON ADVISORY FOR SEAS AT THIS POINT...BUT SUSPECT THAT IT WILL
BE NECESSARY FOR AT LEAST THE NORTHERN WATERS. WINDS BECOME
SOUTHERLY AND INCREASE SUNDAY NIGHT AND MONDAY AHEAD OF AN
APPROACHING FRONTAL SYSTEM THAT WILL CROSS THE WATERS MONDAY
NIGHT. A SMALL CRAFT ADVISORY FOR WINDS LIKELY NEEDED FOR THIS
TIME...AS WELL AS AN ADVISORY FOR HAZARDOUS SEAS ON MONDAY NIGHT
INTO TUESDAY WITH SEAS BUILDING INTO THE 10 TO 12 FT RANGE. CULLEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT SUNDAY FOR WATERS
     FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM 10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 11 PM
     THIS EVENING TO 3 AM PDT SUNDAY.

&&

$$

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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