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 312141
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
240 PM PDT THU JUL 31 2014

.SYNOPSIS...AN UPPER LEVEL RIDGE OVER THE ROCKIES AND GREAT BASIN
WILL REMAIN INTO THE WEEKEND...BEFORE FLATTENING OUT EARLY NEXT
WEEK. A SERIES OF WEAK SHORTWAVE TROUGHS ALOFT WILL LIFT N THROUGH
THE PACIFIC NW OVER THE NEXT FEW DAYS BRINGING A CHANCE FOR
THUNDERSTORMS...MAINLY TO THE CASCADES.
&&

.SHORT TERM...A VERY SLOW MOVING SHORTWAVE WAS SEEN EARLY THIS
AFTERNOON OFF THE N CA AND S OREGON COAST IN WATER VAPOR PICTURES...
WITH AN ALTOCUMULUS FIELD MOVING UP INTO WESTCENTRAL OREGON
SUGGESTING SOME MID LEVEL INSTABILITY IN THE DIFFLUENT AREA AHEAD OF
THE SHORTWAVE. SPC MESOANALYSIS HOWEVER INDICATES BEST INSTABILITY
REMAINS CLOSER TO THE CASCADES. MODEL FORECAST SOUNDINGS HOWEVER DO
SHOW SOME DESTABILIZATION ALOFT LATER TONIGHT BETWEEN THE CASCADES
AND COAST RANGE AS THE SHORTWAVE AND MID LEVEL MOISTURE LIFT N...SO
IN ADDITION TO KEEPING A CHANCE FOR THUNDERSTORMS TONIGHT OVER THE
CASCADES...WILL EXTEND A SLIGHT CHANCE FOR THUNDERSTORMS W TO THE
COAST RANGE. MODELS IN GENERAL INDICATE THE SHORTWAVE LIFTING NE OF
THE REGION FRI MORNING SO WILL INCLUDE A SLIGHT CHANCE FOR
CONVECTION INTO FRI MORNING ACROSS THE N. ADDITIONAL WEAK SHORTWAVES
INDICATED IN MODELS TO FOLLOW SAT AND TO A LESSER EXTENT SUN...BUT
WITH THE MID AND UPPER LEVEL FLOW BECOMING INCREASINGLY SW TO
WESTERLY. EXPECT THIS TO RELEGATE THE THREAT FOR THUNDERSTORMS MORE
TO THE CASCADES FRI AFTERNOON...AND LIMITED MORE TO THE OREGON
CASCADES SAT AND SUN.

THE LACK OF ANY KIND OF MARINE PUSH LAST NIGHT WAS LIKELY RELATED TO
THE SHORTWAVE SITTING OFF THE S OREGON AND N CA COAST. AS THE WAVE
LIFTS N TONIGHT AND FRI THOUGH EXPECT ONSHORE FLOW TO PICK UP
A BIT TONIGHT SUGGESTING MORE MARINE CLOUDS ON THE COAST...AND AN
EVEN BETTER PUSH FRI NIGHT SUGGESTING THE POTENTIAL FOR SOME CLOUDS
PUSHING INLAND BY SAT MORNING...AS WELL AS A FEW DEGREES OF COOLING
BY SAT. A SIMILAR SITUATION SAT NIGHT INTO SUN SUGGESTS AGAIN SOME
MARINE CLOUDS PUSHING INLAND FOR SUN MORNING...AND HIGH TEMPS AGAIN
A BIT COOLER SUN BUT LIKELY STILL ABOVE NORMAL.

.LONG TERM...MODELS IN PRETTY GOOD AGREEMENT IN SHOWING THE REGION
UNDER A WEAK 500 MB FLOW THROUGH MOST OF NEXT WEEK...WITH A
CONTINUATION OF A MODEST LOW LEVEL ONSHORE FLOW AS A RESULT OF THE
HIGH OVER THE NE PACIFIC. OVERALL LOOKS LIKE A DRY PATTERN WITH THE
FLOW ALOFT SEEMING TO FAVOR A LIGHT WESTERLY WIND...AND TEMPS
REMAINING A BIT ABOVE NORMAL.
&&

.AVIATION...HIGH PRESSURE WILL PRODUCE VFR CONDITIONS THROUGH THIS
EVENING. EARLIER MODEL RUNS SUGGESTED THE MARINE LAYER WOULD
SATURATE OFFSHORE THIS EVENING...AND SLIGHTLY STRONGER ONSHORE
FLOW THIS EVENING WOULD RESULT IN LOW CLOUDS PUSHING INTO ALL
COASTAL LOCATIONS OVERNIGHT. HOWEVER...RECENT MODEL GUIDANCE HAS
BACKED OFF ON THIS IDEA SOMEWHAT...DESPITE LOW CLOUDS SKIRTING
THE OLYMPIC PENINSULA COASTLINE THIS AFTERNOON. AS A RESULT...A
LOW CONFIDENCE FORECAST IS IN THE WORKS FOR KAST AND KONP. IN
ADDITION...ELEVATED INSTABILITY WILL RIDE SOUTH TO NORTH ACROSS
THE WILLAMETTE VALLEY OVERNIGHT...BRINGING A THREAT FOR ELEVATED
THUNDERSTORMS TO ALL INTERIOR TAF SITES OVERNIGHT. CONFIDENCE
REMAINS LOW...BUT SUSPECT THE PORTLAND METRO TAF SITES STAND THE
BEST CHANCE OF EXPERIENCING THUNDER TOWARDS 12Z FRIDAY. CONDITIONS
SHOULD OTHERWISE REMAIN VFR FOR INTERIOR TAF SITES THROUGH 00Z
SATURDAY.

KPDX AND APPROACHES...HIGH PRESSURE AND NW FLOW WILL MAINTAIN VFR
CONDITIONS THROUGH 00Z SATURDAY. THERE IS A 30 PERCENT CHANCE
HIGH END IFR CONDITIONS WILL IMPACT THE TERMINAL BETWEEN 13Z AND
17Z FRIDAY. THERE IS A 10 PERCENT CHANCE OF A THUNDERSTORM
IMPACTING THE TERMINAL BETWEEN 06Z AND 18Z FRIDAY. /NEUMAN

&&

.MARINE...ONLY SUBTLE DAY TO DAY VARIATIONS EXPECTED IN THE
WEATHER PATTERN THROUGH THE WEEKEND AS HIGH PRESSURE REMAINS OVER
NORTHEAST PACIFIC. THIS WILL MAINTAIN A TYPICAL SUMMERTIME
PATTERN OF NORTHERLY WINDS...GENERALLY INCREASING EACH AFTERNOON
THROUGH AROUND MIDNIGHT. WILL KEEP SMALL CRAFT ADVISORIES GOING
FOR THE NEAR SHORE WATERS...BUT DECIDED TO DROP THE CENTRAL OREGON
OUTER WATERS WHERE MODELS HAVE BEEN UNDERACHIEVING ALL DAY.

HIGH PRESSURE SAGGING SOUTHWARD FRIDAY AND SATURDAY WILL LIKELY
KEEP SMALL CRAFT ADVISORY LEVEL WIND GUSTS OF 25 KT FROM
MATERIALIZING ACROSS ALL THE WATERS EVEN THOUGH MODEL GUIDANCE
SUGGESTS OTHERWISE.

NONETHELESS...THE GENERAL WEATHER PATTERN WILL CONTINUE TO PRODUCE
LOCALLY GENERATED WIND WAVES/FRESH SWELL....LEADING TO CHOPPY
SEAS...BUT WITH TOTAL WAVE HEIGHTS GENERALLY REMAINING 5 FT OR
LESS. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT
     THIS EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA
     TO CASCADE HEAD OR OUT 10 NM-COASTAL WATERS FROM CASCADE
     HEAD TO FLORENCE OR OUT 10 NM.
&&

$$

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.


&&



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