Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 191635
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
932 AM PDT SAT APR 19 2014

.SYNOPSIS...A  COLD FRONT AT THE COAST THIS MORNING WILL MOVE INLAND
TODAY...CROSSING THE CASCADES BY LATE TODAY. SHOWERS WILL DECREASE
TONIGHT AS THE PARENT UPPER TROUGH MOVES EAST AS WELL. WEAK HIGHER
PRESSURE WILL MOVE IN SUNDAY FOR GENERALLY DRY WEATHER ON
EASTER...EXCEPT SOME MOISTURE MAY BRUSH THE FAR NORTH COAST ZONES.
THE NEXT FRONT WILL BECOME NORTH SOUTH ORIENTED SUNDAY NIGHT AND
STALL OFF THE COAST AS ENERGY DIGS TOWARD CALIFORNIA FOR MORE MOSTLY
DRY WEATHER...BUT THEN MOVE ONSHORE MONDAY AND TUESDAY FOR MORE RAIN
OR SHOWERS. THE REMAINDER OF NEXT WEEK LOOKS UNSETTLED AS MORE
PRECIPITATION MOVES IN AT TIMES. &&

.MORNING UPDATE...QUITE A BIT OF DRY AIR BELOW 700 MB (10K FT OR SO)
ON THE MORNING SALEM SOUNDING BUT LIFT FROM INCOMING MODEST
NEGATIVELY TILTED TROUGH AND UPPER JET IS BEGINNING TO SATURATE THE
LOWER LEVELS. LIKELY SOME SPRINKLES OR LIGHT RAIN AHEAD OF THE MAIN
FRONTAL PRECIPITATION WHICH IS NOW NEARING THE WEST SIDE OF THE
VALLEY. THE BEST DYNAMICS GRAZE THE NW CORNER OF THE AREA WHERE MORE
MODERATE RAIN WILL FALL. THE MAIN BAND OF PRECIP IS NOT VERY LONG
LASTING AND DRY AIR INLAND WILL CONTINUE TO LIMIT PRECIP TOTALS...SO
LIKE THE OCCASIONAL RAIN WORDING TODAY WITH TRANSITION TO SHOWERS
THIS AFTERNOON/EVENING AS IT WILL NOT BE A HUGE SOAKER INALND.
SUBSIDENCE RETUNS QUICKLY BEHIND THE FRONT AND WILL LIMIT SHOWER
ACTIVITY LATER TONIGHT...SO NOT A WHOLE LOT OF SHOWER ACTIVITY BEHIND
THIS FRONT AGAIN WITH OROGRAPHICALLY FAVORED AREAS IN THE NORTH
STANDING THE BEST CHANCE. /KMD

&&

.SHORT TERM...COLD FRONT WAS SEEN ON SATELLITE ABOUT 200 MI OFFSHORE
EARLY SAT MORNING...MAKING STEADY PROGRESS EASTWARD AND ON TRACK TO
REACH THE COAST LATE THIS MORNING. CLOUDS MAINLY MID AND LOW LEVEL
WITH THE FRONT...MATCHING THE MODEL CROSS SECTIONS SUGGESTING
MOISTURE GENERALLY BELOW 700MB. WHILE MOISTURE IS ON THE SHALLOW
SIDE...THE FRONT ITSELF APPEARS MODERATELY STRONG AND IS SYNCHED
WITH A SHORTWAVE ALOFT PROVIDING WELL TIMED LIFT. WILL KEEP POPS
HIGH TODAY FOR THE FRONTAL PASSAGE ALTHOUGH THE DURATION MAY BE ON
THE SHORT SIDE. SATELLITE SHOWS SHOWERS ARE ACTIVE BEHIND THE
FRONT...AND INITIALLY LATE TODAY INTO THIS EVENING LOW LEVEL FLOW IS
ONSHORE FAVORING SHOWERS ESP FOR THE OROGRAPHICALLY FAVORED CASCADES
AND COAST RANGE.

AS A SURFACE HIGH BUILDS IN LATE TONIGHT AND SUN...AND AN INITIALLY
FLAT UPPER RIDGE MOVES ACROSS WILL SEE DRY WEATHER RETURN ALONG WITH
WARMER TEMPS AGAIN FOR SUN. THE PATTERN AMPLIFIES SUN NIGHT AND MON
AS THE NEXT TROUGH IN A PROGRESSIVE PATTERN DIGS OFFSHORE AND THE
DOWNSTREAM RIDGE OVER THE INTERIOR WESTERN STATES BUILDS. AS THE
FLOW OVER THE PACIFIC NW BACKS TO THE SSW MID AND UPPER LEVEL
MOISTURE EXPECTED TO INCREASE. MODEL SOUNDINGS SUGGEST AIR MASS AT
BEST MARGINALLY UNSTABLE...AND WITH DYNAMICS DIGGING THE TROUGH S
PREFER TO LIMIT POPS OUT AHEAD OF THE FRONT MON TO CHANCE CATEGORY
INLAND...BUT HIGHER ALONG THE COAST AS A FRONT AND SHORTWAVE
APPROACH LATE IN THE DAY. SW ONSHORE FLOW COUPLED WITH FALLING
HEIGHTS ALOFT POINT TOWARDS COOLER MARINE AIR PUSHING BACK IN MON.

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
MONDAY NIGHT THROUGH THURSDAY...FLOW CONTINUES TO AMPLIFY SUNDAY
NIGHT AND THIS WILL ORIENT THE COLD FRONT OFFSHORE MORE NORTH TO
SOUTH...THUS ANY PRECIPITATION WILL REMAIN WELL OFFSHORE SUNDAY
NIGHT. THE COLD FRONT FINALLY GETS A SHOVE AS THE UPPER JET NOSES
INTO THE AREA. PRECIPITATION IS MAINLY TIED TO THE FRONT...BUT WITH
THE MARGINALLY UNSTABLE SW FLOW...MODELS SHOW THAT THERE COULD BE
SOME SHOWERS IN THE AFTERNOON MAINLY FOR THE CASCADES...AS MID LEVEL
LAPSE RATES HOVER IN THE 6 TO 7 DEG/KM RANGE. INSTABILITY PARAMETERS
ARE NOT THAT IMPRESSIVE...SO THUNDER POTENTIAL LOOKS LOW AT THIS
TIME.

LOOKS LIKE TUE AND WED WILL BE CHARACTERIZED BY COOL AND DAMP
CONDITIONS AS THE DEEP UPPER LOW MIGRATES ACROSS THE PAC NW AND INTO
THE NRN ROCKIES. AFTER THE FIRST LARGE UPPER TROUGH CLEARS LATE
TUESDAY NIGHT AND MAYBE A BREAK IN SHOWERS WEDNESDAY...ANOTHER DEEP
UPPER LOW WILL SPREAD SEVERAL WAVES OF SHOWER ACTIVITY THROUGH THE
AREA FOR THE LATTER HALF OF THE WEEK.. /KMD
&&

.AVIATION...PACIFIC COLD FRONT APPROACHING THE COAST EARLY THIS
MORNING. PCPN HAS REACHED THE COAST WITH LOW VFR TO MVFR CIGS IN
THE 2500 TO 3500 FT RANGE. RAIN WILL SPREAD TO INLAND TAF SITES
AROUND 18Z WITH OCCASIONAL MVFR CIGS. NAM RH FIELDS AT 925 MB
IMPLY WIDESPREAD MVFR CIGS WITH AND BEHIND THE FRONT THIS
AFTERNOON AND EVENING. THIS MAYBE OVERDONE ESPECIALLY BEHIND THE
FRONT. HIGH PRES BUILDS OVER THE REGION OVERNIGHT SO COULD SEE
PATCHES OF LOW STRATUS OR FOG SUN MORNING.

KPDX AND APPROACHES...VFR PREVAILING THROUGH ABOUT 20Z. THEN
OCCASIONAL MVFR CIGS AROUND 2500-3000 FT THROUGH 00Z OR SO.
EXPECT VFR OVERNIGHT.

&&

.MARINE...A STRONG LOW PRES SYSTEM MOVING INTO THE ALASKA
PANHANDLE WILL PUSH A COLD FRONT ACROSS THE WATERS TODAY WHICH
WILL BRING SMALL CRAFT ADVISORY WINDS OVER ALL WATERS THROUGH THE
DAY. SOME OCCASIONAL GUSTS IN THE 30-35 KT RANGE POSSIBLE NEAR THE
FRONT...WHICH SHOULD PUSH ASHORE BY LATE MORNING. WINDS WILL
DIMINISH LATE THIS AFTERNOON ACROSS THE CENTRAL OREGON WATERS AND
ACROSS THE NORTH THIS EVENING.

A LARGE WESTERLY SWELL TRAIN WILL FOLLOW THE FRONT TONIGHT INTO
SUN. SEAS WILL RAPIDLY INCREASE TO 17 TO 20 FT AT 16 SECONDS WHEN
THE SWELL ARRIVES AROUND 11 PM TONIGHT...AND PEAKING THROUGH 5 AM
SUN. SEAS WILL THEN GRADUALLY SUBSIDE THROUGH SUN
AFTERNOON...DIMINISHING TO AROUND 15 FT SUN NIGHT...AND TO 10 FT
EARLY TUE.

A HIGH SURF ADVISORY CONTINUES FOR SAT NIGHT THROUGH SUN MORNING
FOR THE SOUTH WASHINGTON AND NORTH OREGON COASTS. IT APPEARS THE
CENTRAL COAST WILL ALSO MEET CRITERIA BASED ON POTENTIAL
IMPACTS...SO WILL ISSUE A HIGH SURF ADVISORY FOR THAT AREA. ALL
INDIVIDUALS ALONG THE BEACHES SHOULD EXERCISE CAUTION THIS
WEEKEND.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 10 PM THIS EVENING TO 10 AM PDT SUNDAY
     FOR NORTH OREGON COAST.

     HIGH SURF ADVISORY FROM 2 AM TO 10 AM PDT SUNDAY FOR CENTRAL
     OREGON COAST.

WA...HIGH SURF ADVISORY FROM 10 PM THIS EVENING TO 10 AM PDT SUNDAY
     FOR SOUTH WASHINGTON COAST.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 9 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 4 PM THIS
     AFTERNOON TO 6 AM PDT MONDAY FOR COASTAL WATERS FROM CAPE
     SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 4 PM PDT THIS AFTERNOON
     FOR COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60
     NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL
     10 AM PDT THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 4 PM
     THIS AFTERNOON TO 3 AM PDT SUNDAY.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
    HTTP://WEATHER.GOV/PORTLAND

INTERACT WITH US VIA SOCIAL MEDIA
    WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
    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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