Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 210402
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
902 PM PDT MON OCT 20 2014

.SYNOPSIS...SHOWERS WILL DECREASE TONIGHT AND TUESDAY MORNING AS AN
UPPER TROUGH MOVES EAST OF THE FORECAST AREA. THE NEXT FRONT WILL BE
QUITE WET AS IT SLOWLY MOVES NORTH TO SOUTH THROUGH OUR FORECAST
AREA...SLOWLY SPREADING IN FROM THE NORTHWEST TUESDAY THEN SLOWLY
SINKING SOUTH THROUGH THE FORECAST AREA TUESDAY NIGHT AND WEDNESDAY.
RAIN WILL LIKELY LINGER INTO THURSDAY. THIS FRONT MAY ALSO PRODUCE
STRONG COASTAL WINDS BEGINNING LATE TUESDAY AND CONTINUING INTO
WEDNESDAY MORNING. ANOTHER RATHER WET AND POSSIBLY WINDY FRONT IS
EXPECTED BY THE WEEKEND.
&&

.SHORT TERM...TONIGHT THROUGH THURSDAY...THE AXIS OF AN UPPER TROUGH
WAS MOVING ONSHORE THIS EVENING...AND THE ASSOCIATED INSTABILITY
PRODUCED A COUPLE OF LINES OF SHOWERS AND ISOLATED THUNDERSTORMS THAT
MOVED THROUGH THE VALLEYS IN THE LATE AFTERNOON AND EARLY EVENING
WITH SOME HEAVY DOWNPOURS THAT LIKELY AFFECTED TRAFFIC IN THE EVENING
COMMUTE AND ON AREA FREEWAYS. THE SHOWERS ARE EASING... BUT WILL
STILL HAVE A FEW SHOWERS LINGER INTO EARLY TUESDAY AS THE UPPER
TROUGH FINALLY MOVES EAST OF THE AREA.

ATTENTION THEN TURNS TO THE MOIST ENERGETIC SYSTEM APPROACHING 130W
THIS EVENING THAT HAS A 130 KT OR SO CENTRAL AND EASTERN PACIFIC JET
PUSHING IT ALONG. THE MODELS SHOW THE OVERRUNNING CLOUD SHIELD
STARTING TO REACH THE COAST BY LATE TUESDAY MORNING...AND CONTINUING
TO SPREAD INTO WASHINGTON AND NORTHWEST PART OF OUR FORECAST AREA
THROUGH THE DAY TUESDAY. THE ASSOCIATED FRONTAL BOUNDARY STAYS HUNG
UP OVER WESTERN WASHINGTON AND PERHAPS THE FAR NORTHWEST CORNER OF
OREGON THROUGH TUESDAY NIGHT...THEN SAGS SOUTH THROUGH NORTHWEST
OREGON DURING THE DAY WEDNESDAY INTO WEDNESDAY NIGHT.

THIS SYSTEM HAS A LOT OF MOISTURE WITH IT...AND A STRONG 300 MB JET
IN ADDITION TO STRONG 850 MB INFLOW OR MOISTURE TRANSPORT WINDS. LOOK
FOR SUBSTANTIAL RISES ON AREA RIVERS...WITH THE MOST PRONE TO BE
FLASHY RIVERS LIKE THE GRAYS RIVER IN WAHKIAKUM COUNTY IN SOUTHWEST
WASHINGTON. HOWEVER...THE FRONT DOES MOVE ENOUGH AS IT MOVES SOUTH
THROUGH OUR FORECAST AREA THAT IT MAY KEEP MOST RIVERS FROM FLOODING.
THE BIGGEST PROBLEM WILL PROBABLY BE URBAN AND SMALL STREAM
FLOODING...WHICH WILL BE MUCH MORE LIKELY...EXACERBATED BY THE
CURRENT CROP OF FALLING LEAVES PLUGGING STORM DRAINS.

THERE IS A GOOD WAVE OR POSSIBLE LOW CENTER THAT THE NAM12 AND GFS
MODELS CONTINUE TO FORECAST WILL RIDE ALONG THE FRONTAL ZONE TOWARD
VANCOUVER ISLAND TUESDAY NIGHT. HAVE ISSUED A HIGH WIND WATCH FOR THE
HEADLANDS AND BEACHES FOR FOR LATE TUESDAY INTO EARLY WEDNESDAY FOR
THIS.

THE FRONT SAGS SLOWLY INTO SOUTHERN OREGON WEDNESDAY NIGHT AND
THURSDAY...WITH THE PRECIPITATION BREAKING UP MUCH OF OUR AREA BY
THURSDAY. HOWEVER...THERE IS ENOUGH ENERGY ROTATING AROUND THE
OFFSHORE LONG WAVE TROUGH TO KEEP SOME PRECIPITATION GOING ON
THURSDAY AS WELL. TOLLESON

.LONG TERM...THURSDAY NIGHT THROUGH SUNDAY...NO CHANGES...PREVIOUS
DISCUSSION FOLLOWS. MEDIUM RANGE GUIDANCE CONTINUE TO STRUGGLE WITH
HOW TO HANDLE THE LATE WEEK AND WEEKEND PERIOD...WITH THE 00Z
GFS/ECMWF/GEM SEEMING TO TREND TOWARD SHIFTING THE LONGWAVE PATTERN
TO FAVOR TROUGHING OVER WESTERN NORTH AMERICA. THIS WOULD BE A
SIGNIFICANT SHIFT FROM THE OVERALL LONGWAVE RIDGING PATTERN THAT HAS
DOMINATED THE WEST FOR THE PAST SEVERAL MONTHS. AS SUCH...THE 00Z
GFS/ECMWF NOW BRING ANOTHER UPPER TROUGH ACROSS THE PAC NW FOR MORE
SHOWERS AND COOL TEMPS THROUGH THE WEEKEND. AM A BIT SKEPTICAL OF
THIS LARGE SCALE PATTERN SHIFT... ESPECIALLY CONSIDERING THE LARGE
POOL OF ABOVE NORMAL SEA SURFACE TEMPS OVER THE NE PACIFIC. THEREFORE
WE REMAIN A BIT CONSERVATIVE... KEEPING POPS/TEMPS CLOSER TO CLIMO
OVER THE WEEKEND THAN THESE 00Z MODELS WOULD SUGGEST. WEAGLE
&&

.AVIATION...MAINLY VFR CONDITIONS WITH OCCASIONAL MVFR AND MOUNTAIN
OBSCURATION IN SCATTERED SHOWERS THROUGH THE NIGHT. THERE SHOULD BE A
LULL IN THE SHOWERS TUE MORNING BEFORE THE RAIN RETURNS TO THE COAST
BY LATE MORNING WITH GRADUALLY LOWERING CONDITIONS AT THE COAST.
WINDS WILL ALSO BE AN ISSUE ON THE COAST WITH SURFACE WINDS LIKELY
GUSTING TO 40 KT AT TIMES TUE NIGHT THROUGH WED MORNING.
INLAND...RAIN CHANCES INCREASE IN THE AFTERNOON BECOMING LIKELY BY
LATE AFTERNOON OR EARLY EVENING.

KPDX AND APPROACHES...VFR PREVAILING THROUGH TUE. THERE IS A 30
PERCENT CHANCE OF MVFR CIGS BETWEEN 2000 AND 3000 FT BETWEEN 12Z AND
18Z.
&&

.MARINE...MARGINAL SMALL CRAFT ADVISORY WINDS WILL CONTINUE THIS
EVENING MAINLY WITH GUSTS TO 25 KT BUT WILL KEEP ADVISORY GOING UP TO
THE EXPECTED GALES BEGINNING TUE AFTERNOON. THERE ARE STILL
DIFFERENCES BETWEEN THE MODELS AS TO THE STRENGTH...SOME LOW END
GALES AND ONE OTHERS LIKE THE NAM IS SHOWING HIGHER END GALES TUE
NIGHT INTO WED MORNING. THE NAM BRINGS ANOTHER LOW TO THE NORTH
OREGON COAST WED MORNING...THIS IS AN OUTLIER RIGHT NOW BUT BEARS
WATCHING GIVEN THE ACTIVE JET OVER THE NORTH PACIFIC.  A COASTAL JET
IS EXPECTED TO FORM AHEAD OF AN OCCLUDED FRONT TUE NIGHT ENHANCING
WINDS NEAR THE COAST.

A WESTERLY SWELL ON THE ORDER OF 10 FT WILL CONTINUE FOR THE NEXT FEW
DAYS...BUT SEAS ARE LIKELY TO BUILD TO AROUND 15 TO 18 FT AND BECOME
STEEPER TUE NIGHT AND WED DUE TO THE SOUTHERLY GALES.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     MORNING FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...HIGH WIND WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
     MORNING FOR SOUTH WASHINGTON COAST.

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

     GALE WARNING FROM 1 PM TUESDAY 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 TUESDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL
     6 PM PDT TUESDAY.

&&

$$

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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