Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 202156
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
257 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 TUESDAY NIGHT AND WEDNESDAY...WITH RAIN LIKELY LINGERING INTO
THURSDAY. THIS FRONT MAY ALSO PRODUCE STRONG COASTAL WINDS. ANOTHER
FRONT IS EXPECTED BY THE WEEKEND.

&&

.SHORT TERM...TONIGHT THROUGH THURSDAY...LOW PRESSURE TROUGH AXIS
HAS PUSHED JUST INSIDE 130W ALONG THE PACNW COAST. THE BACK EDGE OF
A N/S ORIENTED FRONT IS LOCATED OVER THE HIGHER CASCADES. DECENT
CLEARING BEHIND THE FRONT IS ALLOWING FOR CONVECTION TO DEVELOP WITH
SOME SHOWERS BECOMING HEAVY AT TIMES. THERE MAY BE ENOUGH HEATING TO
RESULT IN THE OCCASIONAL LIGHTNING STRIKE EAST OF THE COAST RANGE
BUT BEST CHANCE FOR THUNDERSTORMS WILL BE OVER THE WATERS THROUGH
EVENING. SHOWERS AND ANY THUNDERSTORMS WILL DIMINISH AS THE UPPER
TROUGH WEAKENS AND ALSO WITH THE LOSS OF DAYTIME SURFACE HEATING.

SHORTWAVE ENERGY FROM THE CURRENT TROUGH IS DIGGING A BIT FURTHER
SOUTH THAN PREVIOUS MODEL RUNS INDICATED. AS SUCH...TUESDAY APPEARS
THE REGION WILL BE UNDER MORE ZONAL FLOW WITH THE SHORT WAVE RIDGING
HAVING DRIFTED A BIT FURTHER SOUTH THAN IN RECENT RUNS. IS ALL... STILL
POTENTIALLY A PLEASANT DAY THROUGH THERE WILL BE SOME LINGERING
SHOWERS.

MORNING MODEL RUN DATA MAINTAINS CONFIDENCE IN A BROAD PACIFIC
TROUGH AND ASSOCIATED SLOW MOVING AND MOISTURE LADEN FRONT CROSSING
THE AREA OVER THE NEXT FEW DAYS. CURRENT QPF FORECAST LOOKS FAIRLY
GOOD AGAINST THE RECENT RUNS. ESRL REFORECAST ANALOGS OF SIMILAR
PAST EVENTS PROVIDE SIMILAR QPF AMOUNTS AND PATTERN GIVING FURTHER
CONFIDENCE OF TOTAL RAIN FOR THE NEXT 72 HOURS. OUR QPF FORECAST
CALLS FOR 2 TO 5 INCHES THROUGHOUT THE FORECAST AREA BY THE TIME
RAIN TAPERS OFF THURSDAY. HEAVIEST RAIN WILL BE IN THE COAST RANGE
AND THE S WA CASCADES. THIS MAY BE ENOUGH TO CAUSE SOME FLOOD THREAT
FOR OUR MORE RESPONSIVE RIVERS SUCH AS THE GRAYS RIVER DRAINING OUT
OF THE WILLAPA HILLS. OF COURSE WE WILL MONITOR THIS CLOSELY AND
WILL HAVE A BETTER IDEA ON THE RAINFALL DISTRIBUTION AS WE GET
CLOSER TO THE EVENT.

THERE WILL BE MULTIPLE EMBEDDED SHORT WAVES BRINGING PERIODS OF
GUSTY WINDS TO AROUND 50 MPH ALONG THE COAST TUESDAY EVENING AND
AGAIN WEDNESDAY NIGHT. STRONG PARENT SURFACE LOW WILL STAY WELL
OFFSHORE WITH A PRIMARILY SOUTHEAST GRADIENT ACROSS THE COASTLINE.
THIS TYPICALLY RESULTS IN A BEACHES AND HEADLANDS FOCUS FOR THE
WINDS. THE SLIGHTLY INLAND COASTAL COMMUNITIES MAY GET A SHORT
PERIOD OF THE HIGHER WINDS LATE TUESDAY EVENING WITH PERHAPS A
BETTER EXPOSURE ON WEDNESDAY NIGHT/THURSDAY. /JBONK


LONG TERM...THURSDAY NIGHT THROUGH SUNDAY... MINIMAL
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 ACROSS NW OREGON THIS AFTERNOON.
SCATTERED SHOWERS EXPECTED TO CONTINUE THROUGH THE NIGHT...BUT
SLOWLY DECREASING IN COVERAGE. SHOWERS WILL CONTINUE TO BRING
LOCALLY MVFR CONDITIONS AND MOUNTAIN OBSCURATIONS. ISOLATED
THUNDERSTORMS WILL BE POSSIBLE NEAR THE COAST THROUGH 02Z.

KPDX AND APPROACHES...VFR TONIGHT AND EARLY TUE...BUT OCCASIONAL
SHOWERS WILL CONTINUE TO BRING A RISK FOR BRIEF MVFR CONDITIONS...
MOST LIKELY EARLY TONIGHT THROUGH 05Z.
&&

.MARINE...WINDS GUSTING OUT OF THE S WILL CONTINUE TO FLIRT WITH
SMALL CRAFT CRITERIA TONIGHT AND TUE MORNING. WINDS WILL PICK UP
WITH THE NEXT FRONTAL SYSTEM TUE AFTERNOON. GALES APPEAR LIKELY WITH
THIS SYSTEM...AND EXPECTED TO CONTINUE UNTIL AN OCCLUDED FRONT MOVES
ONTO THE N OREGON AND S WA COAST LATE TUE NIGHT OR EARLY WED...
BEFORE STALLING ALONG THE CENTRAL OREGON COAST. BEST GUESS AT THIS
POINT IS FOR THE FRONT TO REACH THE COLUMBIA RIVER BAR AROUND 3 AM
TUE NIGHT. A COASTAL JET IS EXPECTED TO FORM AHEAD OF THE 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 SOME AND BECOME STEEPER TUE
NIGHT DUE TO THE SOUTHERLY GALES.
&&


.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
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 5 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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