Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 272137
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
236 PM PDT THU AUG 27 2015

.SYNOPSIS...AFTER ONE MORE NICE DAY TODAY...ATTENTION TURNS TOWARD
OUR UPCOMING BIG CHANGE IN THE WEATHER. A LOW PRESSURE SYSTEM
CENTERED OFF THE OREGON COAST WILL SPREAD THE FIRST WAVE OF RAIN INTO
THE COASTAL WATERS TONIGHT AND TO THE COAST LATE TONIGHT AND
FRIDAY...SPREADING INLAND SOME FRIDAY BEFORE LIFTING NORTH LATER IN
THE DAY. THE MOST SIGNIFICANT WAVE WILL LIFT NORTH THROUGH THE AREA
FRIDAY NIGHT AND SATURDAY MORNING FOR MORE RAIN. THE MODELS ARE
INCREASINGLY INDICATING THAT THIS WAVE WILL BE ASSOCIATED WITH A
RATHER STRONG SURFACE LOW THAT WILL BRING WINDY CONDITIONS TO NEARLY
ALL OF SOUTHWEST WASHINGTON AND NORTHWEST OREGON LATE FRIDAY NIGHT
AND SATURDAY MORNING. ANOTHER FRONT WILL SWEEP IN FROM THE WEST
SATURDAY NIGHT INTO EARLY SUNDAY FOR ANOTHER PERIOD OF RAIN.
UNSETTLED WEATHER WILL CONTINUE AT TIMES INTO NEXT WEEK AS A TROUGH
REMAINS NEAR THE COAST.
&&

.SHORT TERM...SOUTHWEST WASHINGTON AND NORTHWEST OREGON IS SEEING
ANOTHER SUMMER LIKE DAY TODAY UNDER SOUTHWEST FLOW ALOFT...KEEPING
THE THREAT OF ANY THUNDER EAST OF OUR FORECAST AREA WHILE ALLOWING
TEMPS TO STILL RISE ABOVE NORMAL THIS AFTERNOON...WITH MID TO UPPER
80S INLAND.

THE BIG CHANGE THAT HAS BEEN ADVERTISED FOR FRIDAY AND THIS WEEKEND
STILL LOOKS ON TRACK...THOUGH SOME SUBTLE CHANGES CONTINUE TO CREEP
INTO RECENT MODEL RUNS. THE MAIN CENTER OF LOW PRESSURE IS STILL
CENTERED OUT AROUND CLOSE TO 140W AND A BIT NORTH OF 40N THIS
AFTERNOON...WITH A FRONTAL BOUNDARY ALONG ABOUT 128W. SOME
PRECIPITATION WAS ROTATING NORTH ALONG THE BOUNDARY. ADDITIONAL RAIN
WILL SPREAD INTO OUR COASTAL WATERS TONIGHT WITH A WAVE LIFTING
NORTH...LIKELY REACHING THE COAST LATE TONIGHT...AND SPREADING INLAND
ESPECIALLY IN THE NORTH ON FRIDAY BEFORE LIFTING NORTH LATER IN THE
DAY FRIDAY.

AFTER A BRIEF LULL LATE FRIDAY AFTERNOON AND FRIDAY EVENING...THE
STRONGEST WAVE OF THE SERIES WILL BE LIFTING NORTH ALONG THE COAST
AND THROUGH THE FORECAST AREA LATE FRIDAY NIGHT AND SATURDAY MORNING.
THE MODELS...ESPECIALLY THE GFS13 AND NOW THE 12Z ECMWF... INDICATE A
RATHER STRONG SURFACE LOW TO LIFT NORTH ALONG THE COAST AND THROUGH
THE AREA LATE FRIDAY NIGHT AND SATURDAY MORNING. IF SO...IT COULD
BRING GALES TO THE COASTAL WATERS...HIGH WIND TO THE COAST AND
POSSIBLY THE COASTAL MOUNTAINS...AND WINDY CONDITIONS FARTHER INLAND.
WILL BE ISSUING A HIGH WIND WATCH FOR THE COAST AND COASTAL MOUNTAINS
FOR LATE FRIDAY NIGHT AND SATURDAY MORNING WITH THIS FORECAST
PACKAGE.

AFTER THE PRECIPITATION TURNS TO SHOWERS AND EASES SATURDAY
AFTERNOON...ANOTHER FRONT WILL SWING IN FROM THE WEST SATURDAY NIGHT
FOR A ANOTHER PERIOD OF STEADY RAIN. SHOWERS WILL FOLLOW BEHIND ON
SUNDAY...ESPECIALLY ACROSS THE NORTHERN FORECAST ZONES.

THESE SYSTEMS...ESPECIALLY THE ONE LATE FRIDAY NIGHT AND SATURDAY
MORNING...WILL HAVE SUBSTANTIAL DYNAMICS WITH THEM. PRECIPITABLE
WATER VALUES FEEDING IN FRIDAY NIGHT AND SATURDAY CONTINUE TO BE
FORECAST TO BE NEAR 1.5 INCHES...ACCOMPANIED BY A 110 KT 300 MB JET
STREAK LATE FRIDAY NIGHT AND SATURDAY MORNING. 850 MB INFLOW IS
AROUND 25 KT WITH THE INITIAL SURGE OF MOISTURE TONIGHT AND
FRIDAY...THEN IS AROUND 60 KT ON THE GFS AND ECMWF AS THE SURFACE LOW
MOVES THROUGH...GIVING SUPPORT TO THE HIGH WIND. ALL IN ALL...THIS
LOOKS QUITE WET...THOUGH THE WINDY SYSTEM FRIDAY NIGHT AND SATURDAY
MORNING MIGHT NOT BE QUITE AS WET AS PREVIOUS EXPECTED.

RAINFALL ACCUMULATIONS THROUGH THE ENTIRE WEEKEND ARE LIKELY TO BE IN
THE 1 TO 2 INCH RANGE ALONG THE COAST...IN THE COAST RANGE...AND IN
THE SOUTH WASHINGTON CASCADES...0.75 TO 1.5 INCHES IN THE OREGON
CASCADES...AND IN THE 0.5 TO 0.75 INCH RANGE IN THE VALLEYS. THE
HEAVIES AMOUNTS WILL TEND TO BE ON THE SOUTH WASHINGTON COAST...AND
THE LOWER AMOUNTS IN THE CENTRAL OREGON CASCADES. THIS WILL LIKELY
PUT A HUGE DENT IN THE FIRE WEATHER SEASON FOR OUR AREA FOR AT LEAST
THE NEXT COUPLE OF WEEKS. TOLLESON

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY. FALL-LIKE WEATHER PATTERN
CONTINUES INTO NEXT WEEK WITH PRIMARILY COOLER THAN NORMAL
TEMPERATURES...CLOUDY CONDITIONS...AND CHANCES FOR ADDITIONAL RAIN.
ON MONDAY A SHORTWAVE MOVING THROUGH TO OUR NORTH MAY CLIP US WITH
SOME RAIN MAINLY ON THE COAST AND INLAND NORTH WHILE THE REST OF THE
AREA SHOULD REMAIN MOSTLY DRY. HAVE LEFT A SLIGHT CHANCE FOR RAIN
ACROSS MOST OF THE AREA JUST IN CASE THE MODELS DON`T QUITE HAVE THE
RIGHT TRACK FOR THIS SHORTWAVE SINCE IT`S A FEW DAYS OUT. MODELS ARE
HONING IN ON ANOTHER LOW PRESSURE SYSTEM THAT WILL MOVE THROUGH
TUESDAY NIGHT INTO WEDNESDAY WHICH COULD PRODUCE ANOTHER SOAKING RAIN
ACROSS THE AREA. BEHIND THIS SYSTEM TEMPERATURES COOL DOWN A BIT MORE
WITH MAYBE A FEW SHOWERS LINGERING INTO THURSDAY. -MCCOY
&&

.AVIATION...DRY SOUTHWEST FLOW WILL BECOME INCREASINGLY MOIST THROUGH
00Z SATURDAY AND PRODUCE LOWERING CEILINGS ACROSS THE REGION. EXPECT
MVFR STRATUS AND OCCASIONAL BOUTS OF IFR STRATUS TO PUSH ONTO THE
COAST LATER THIS EVENING...LIKELY LINGERING FOR MUCH OF THE DAY ON
FRIDAY. A WEAK SURFACE TROUGH SHIFTING INLAND ON FRIDAY MAY ENABLE
SOME OF THE STRATUS ALONG THE COAST TO PUSH INTO THE WILLAMETTE
VALLEY LATE FRIDAY MORNING/MIDDAY...ESPECIALLY ACROSS THE NORTH. THIS
MAY PRODUCE A PERIOD OF MVFR CONDITIONS ACROSS THE INTERIOR...BUT
CONFIDENCE REMAINS LOW.

KPDX AND APPROACHES...DRY SOUTHWEST FLOW WILL BECOME INCREASINGLY
MOIST FRIDAY. THERE IS A CHANCE OF MVFR CONDITIONS DEVELOPING LATE
FRIDAY MORNING/MIDDAY...BUT CONFIDENCE IN THIS SCENARIO REMAINS LOW
AT THIS POINT. /NEUMAN
&&

.MARINE...EXPECT RELATIVELY BENIGN CONDITIONS ON FRIDAY TO ABRUPTLY
CHANGE FRIDAY NIGHT. WHILE UNCERTAINTY STILL EXISTS...ESPECIALLY IN
REGARDS TO DETAILS...CONFIDENCE IS GROWING THAT THE WATERS WILL
EXPERIENCE A VERY UNUSUAL FOR THIS TIME OF THE YEAR LOW PRESSURE
SYSTEM...SOMETHING THAT HAS NOT BEEN OBSERVED IN AT LEAST THE PAST 30
YEARS THIS EARLY IN THE SEASON. THIS LOW PRESSURE SYSTEM APPEARS
LIKELY TO DEVELOP OFF THE CALIFORNIA COAST AND MOVE NORTHEASTWARD OFF
THE OREGON COAST BEFORE MAKING LANDFALL NEAR THE OLYMPIC PENINSULA.
THIS WILL RESULT IN SOUTH WINDS INCREASING ABRUPTLY ACROSS THE WATERS
LATE FRIDAY NIGHT OR EARLY SATURDAY MORNING FROM SOUTH TO NORTH. GALE
FORCE WIND GUSTS OF 35 TO 40 KT APPEAR LIKELY DURING THIS
PERIOD...WITH EVEN 45 TO 50 KT WINDS NOT OUT OF THE QUESTION. A GALE
WATCH WAS ISSUED FOR NOW...BUT DEPENDING ON DETAILS THAT STILL NEED
TO BE IRONED OUT...A STORM WARNING MAY BE NEED FOR AT LEAST A PART OF
THE WATERS DURING THE LATE FRIDAY NIGHT OR EARLY SATURDAY MORNING
HOURS. EITHER WAY...THIS UPCOMING STORM SYSTEM IS VERY UNUSUAL FOR
THIS TIME OF YEAR...AND IS SOMEWHAT REMINISCENT OF ONE OF OUR BIGGEST
MARINE EVENTS LAST YEAR...OCTOBER 25TH 2014...WHERE SEAS ROSE 15 TO
20 FT IN 3 TO 4 HOURS AT BUOYS OFF THE OREGON COAST.

ANYWAY...ONCE THE LOW PRESSURE PUSHES ASHORE IN THE PACIFIC
NORTHWEST...A SECOND UNUSUALLY STRONG FRONTAL STORM SYSTEM WILL PUSH
INTO THE WATERS SATURDAY AFTERNOON AND EVENING. THIS SHOULD PRODUCE
ANOTHER ROUND OF 15 TO 25 KT WINDS WITH GUSTS OF 30 TO 35 KT. WINDS
AND SEAS SHOULD THEN RELAX ACROSS THE WATERS SATURDAY NIGHT AND EARLY
SUNDAY.

ADDITIONAL BOUTS OF SMALL CRAFT ADVISORY LEVEL WINDS OF 20 TO 30 KT
APPEAR LIKELY THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. TIMING IN
THESE ADDITIONAL SURGES IN WINDS REMAINS UNCERTAIN AT THIS
POINT...BUT SUNDAY NIGHT AND EARLY TUESDAY APPEAR THE PRIMARY WINDOWS
OF CONCERN. THESE PERIODS OF HIGHER WINDS SHOULD KEEP SEAS FLIRTING
WITH THE 10 FT MARK THROUGH THE MIDDLE OF NEXT WEEK. /NEUMAN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     AFTERNOON FOR NORTH OREGON COAST.

     HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     AFTERNOON FOR CENTRAL COAST RANGE OF WESTERN OREGON-COAST
     RANGE OF NORTHWEST OREGON.

     HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY MORNING
     FOR CENTRAL OREGON COAST.

WA...HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     AFTERNOON FOR SOUTH WASHINGTON COAST.

     HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY
     AFTERNOON FOR WILLAPA HILLS.

PZ...GALE WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

&&

$$

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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