Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 230957 CCA
AFDPQR

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE PORTLAND OR
257 AM PDT TUE SEP 23 2014

.SYNOPSIS...CLOUDY SKIES AND SHOWERS WILL CONTINUE TODAY AS A WEAK
FRONT DISSIPATES OVER THE AREA. A STRONGER AND MORE MOIST FRONT WILL
PRODUCE MORE SUBSTANTIAL RAIN TONIGHT INTO WEDNESDAY. AN UPPER
TROUGH WILL MAINTAIN COOL AND SHOWERY WEATHER THROUGH FRIDAY. AN
UPPER RIDGE SHOULD BRING DRIER WEATHER FOR THE WEEKEND...BUT THERE IS
A LOT OF UNCERTAINTY IN THE FORECAST BEYOND FRIDAY.

&&

.SHORT TERM...TODAY THROUGH FRIDAY...SATELLITE IMAGERY SHOWS A
WELL-DEFINED LOW NEAR 45N 141W EARLY THIS MORNING...WITH AN
ASSOCIATED COLD FRONT SLOWLY APPROACHING THE WASHINGTON AND OREGON
COAST. AN UPPER LEVEL SHORTWAVE AHEAD OF THIS LOW HAS RESULTED IN
CONVECTIVE SHOWERS ACROSS NW OREGON OVERNIGHT. THE SHOWERS HAVE
MOSTLY MOVED INTO WASHINGTON EARLY THIS MORNING...BUT ISOLATED TO
SCATTERED SHOWERS ARE STILL POSSIBLE FOR NW OREGON THROUGHOUT THE DAY
AS A WEAK FRONTAL ZONE ASSOCIATED WITH THIS FIRST SHORTWAVE
DISSIPATES OVER WESTERN WA/OR.

THE NEXT...MORE IMPRESSIVE FRONT WILL BEGIN TO SPREAD RAIN AND GUSTY
WINDS TO THE COAST EARLY THIS EVENING AND SLOWLY MOVE INLAND TONIGHT
INTO WED MORNING. THIS WILL BE THE FIRST FALL-LIKE STORM OF THE
SEASON WITH WINDS AND RAINFALL TOTALS BEING CLOSELY MONITORED.
MODELED SURFACE PRESSURE GRADIENTS STILL APPEAR TOO EAST-WEST
ORIENTED TO PRODUCE STRONG WINDS FOR THE ENTIRE COAST AND THINK GUSTY
WINDS WILL BE MOST NOTICEABLE FOR THE BEACHES AND HEADLANDS WHERE THE
NAM STILL SHOWS THE POTENTIAL FOR A COASTAL JET TO PRODUCE NEAR HIGH
WIND CRITERIA GUSTS.

THIS FRONT IS TAPPING INTO SUBTROPICAL MOISTURE AS IT MOVES ACROSS
THE PACIFIC. THE COMBINATION OF THIS MOISTURE. WITH ISENTROPIC LIFT
AND OROGRAPHIC ENHANCEMENT PROVIDES THE POTENTIAL FOR 1 TO 2 INCHES
OF RAIN ACROSS THE HIGHER TERRAIN OF NW OREGON AND SW WASHINGTON
TUESDAY NIGHT THROUGH WEDNESDAY AFTERNOON...AND UP TO AN INCH
POSSIBLE FOR THE LOW LANDS. THE RAIN WILL STALL OVER THE CASCADES
WEDNESDAY AFTERNOON AND NIGHT WITH RAIN TURNING TO SHOWERS WEST OF
THE CASCADES.

WILL NEED TO MONITOR BURN SCAR AREAS FOR THE POTENTIAL FOR DEBRIS
FLOWS/FLASH FLOODING...PARTICULARLY ALONG THE CLACKAMAS RIVER HIGHWAY
WHICH IS IN A STEEP CANYON TO BEGIN WITH.

THE MAIN FRONTAL ZONE WILL SLOWLY SHIFT EAST OF THE CASCADES
THURSDAY. THE UPPER LEVEL TROUGH OFFSHORE WILL BECOME MORE NEGATIVELY
TILTED THURSDAY AND INCREASE THE CHANCES FOR CONVECTIVE SHOWERS OVER
THE AREA. COOLER THAN NORMAL TEMPERATURES WILL PERSIST.

MODELS HINT THAT THE UPPER TROUGH WILL SPLIT FRIDAY...SENDING MOST OF
ITS ENERGY NORTH AND SOUTH OF THE PORTLAND FORECAST AREA. THIS WILL
LEAD TO A DECREASE IN SHOWER CHANCES...BUT LEFT A CHANCE IN THE
FORECAST DUE TO THE UNCERTAINTY OF THE PATH OF THE UPPER LOW. IF IT
TRACKS ANY FARTHER SOUTH THAN THE 00Z MODELS SUGGEST...NW OREGON WILL
HAVE MORE SHOWERS THAN THEY CURRENTLY SUGGEST.

.LONG TERM...FCST CONFIDENCE DECREASES CONSIDERABLY AS WE GO INTO
NEXT WEEKEND. THE LAST FEW RUNS OF THE GFS MOVE THE UPPER LEVEL LOW
OFF TO THE EAST AND SHOW UPPER LEVEL RIDGING NOSING INTO THE PAC NW.
THIS WOULD BRING WARMER AND DRIER CONDITIONS TO THE PAC NW FOR SAT
AND SUN. MEANWHILE...THE ECMWF AND CANADIAN MODELS ARE TENDING TO
KEEP THE MUCH COOLER AND SHOWERY WEATHER IN PLACE THROUGH THE
WEEKEND. GIVEN THE VARIETY OF MODEL SOLUTIONS...WILL JUST KEEP A
MIDDLE OF THE ROAD FCST WITH MODERATE TEMPS AND SLIGHT CHANCES FOR
SHOWERS IN PLACE FOR SAT AND SUN. UPPER LEVEL LOW PRESSURE OVER THE
GULF OF ALASKA IS MODELED TO BRING THE NEXT FRONT INTO THE PAC NW
EITHER LATE IN THE WEEKEND OR EARLY NEXT WEEK...DEPENDING ON WHETHER
THE WEEKEND PAC NW RIDGING DEVELOPS. THE BRUNT OF THIS FRONT IS
EXPECTED TO REMAIN TO OUR NORTH.  PYLE

&&

.AVIATION...VFR CONTINUES ACROSS THE REGION THIS AM...BUT WILL
HAVE A FEW OCCASIONAL POCKETS OF MVFR CIGS ALONG THE COAST.
SCATTERED SHOWERS MAINLY OVER THE COAST AND COAST RANGES. SUSPECT
WILL CONTINUE TO SEE VERY ISOLATED TSTORMS IN THAT AREA TODAY. AS
NEXT STRONGER FRONT APPROACHES LATER TODAY AND THIS EVENING...WILL
HAVE INCREASING MVFR CIGS WITH RAIN INCREASING. WILL ALSO HAVE
INCREASING SOUTH WINDS ALONG THE COAST...WITH GUSTS 30 TO 40 KT.

KPDX AND APPROACHES...VFR TODAY WITH OCCASIONAL SHOWERS MAINLY
THIS MORNING. CLOUDS WILL THICKEN AND LOWER AFTER 00Z AS NEXT
FRONT APPROACHES. STEADY RAIN LIKELY TO DEVELOP BY 07Z TONIGHT.
ROCKEY.
&&

.MARINE...NOT MUCH IN WAY OF CHANGES. SMALL CRAFT ADVISORY UP
TODAY FOR GUSTY S TO SE WINDS. SEAS MOSTLY 4 TO 6 FT.

BIG STORY WILL THE APPROACHING FRONT TONIGHT. SOUTH WINDS WILL
INCREASE LATER TODAY...WITH STRONGER WINDS DEVELOPING THIS
EVENING. STILL LOOKS REASONABLE THAT WILL HAVE SOLID GALE FORCE
SOUTHERLIES TONIGHT...WITH STRONGEST WINDS PROBABLY IN 7 PM TO
MIDNIGHT TIME FRAME. AFTERWARDS...FRONT PUSHES ONSHORE. BUT WILL
MAINTAIN MODERATELY STRONG S TO SE PRESSURE GRADIENT OVERNIGHT. SO
WILL KEEP GALE FORCE WINDS CONTINUING.

ANOTHER FRONT MOVES ONSHORE ON WED...WITH ANOTHER ROUND OF LOW END
GALE FORCE WINDS FOR WED AFTERNOON AND EVENING.

SEAS BELOW 7 FT TODAY...BUT WILL INCREASE TONIGHT AS THE WINDS
KICK UP. LIKELY TO TOP AT AT 10 TO 13 FT TONIGHT. HOWEVER...THE
MAIN FETCH AREA OF SWELL WILL ARRIVE ON EARLY WED. WEST SWELL
BUILDING TO 15 TO 18 FT WED AM WITH THE LARGE SWELL OVER THE OUTER
WATERS. WITH WINDS...THIS MAKES COMBINED SEAS AT 14 FT NEARSHORE
AND CLOSE TO 20 FT OVER THE OUTER WATERS. SEAS GRADUALLY SUBSIDE
LATER WED NIGHT...BUT STAY ABOVE 10 FT THROUGH FRI. ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FOR LATE THIS AFTERNOON THROUGH TONIGHT ON ALL
 COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR WINDS TODAY ON ALL COASTAL WATERS.

&&

$$

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 AS THE FORECAST AREA.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.