Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 270343
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
842 PM PDT TUE MAY 26 2015

.SYNOPSIS...AN UPPER LEVEL LOW PRES SYSTEM CENTERED OVER EASTERN WA
WILL MOVE SLOWLY SE INTO IDAHO TONIGHT AND WED. THE LOW WILL THEN
MOVE OFF TO THE E AS A RIDGE OF HIGH PRES BUILDS INTO THE REGION FROM
OFF THE PACIFIC. LOW LEVEL ONSHORE FLOW WILL GRADUALLY WEAKEN DURING
THE COURSE OF THE WEEK...RESULTING IN PROGRESSIVELY FEWER CLOUDS AND
WARMING TEMPS HEADING INTO THE WEEKEND. UPPER LEVEL LOW PRES WILL
LIKELY BRING COOLER TEMPERATURES...MORE CLOUDS...AND INCREASING
SHOWERS LATE IN THE WEEKEND AND EARLY NEXT WEEK.
&&

.SHORT TERM...TONIGHT THROUGH FRIDAY...EVENING UPDATE...HAVE HAD A
FEW CLOSE CALLS LATE THIS AFTERNOON AND EARLIER THIS EVENING WITH
ISOLATED THUNDERSTORMS TRYING TO SNEAK OVER THE SW WASHINGTON
CASCADES. MUCH OF THE ACTIVITY STAYED EAST OF THE CASCADES...BUT MOST
LIKELY SAW BRIEF HEAVY RAIN EARLIER THIS AFTERNOON. THE UPPER LEVEL
LOW CONTINUES TO SLOWLY ROTATE OVER FAR EASTERN WASHINGTON THIS
EVENING AND THROUGH TONIGHT...WITH THUNDERSTORMS DRIFTING FURTHER
AWAY FROM OUR FORECAST AREA BORDER. MARINE STRATUS DISSIPATED QUITE A
BIT TODAY...WITH MOST LOCATIONS SEEING SUN THROUGH EARLY THIS
EVENING. MARINE STRATUS HAS ALREADY RETURNED TO THE CENTRAL OREGON
COAST...AND WILL GRADUALLY SPREAD NORTH ALONG THE COAST AND THROUGH
THE COASTAL GAPS OVERNIGHT. THE REMAINDER OF THE FORECAST REMAINS
VALID.../27

THE CLOSED LOW WILL CONTINUE TO DRIFT EASTWARD INTO IDAHO TONIGHT AND
WED. THIS WILL ALLOW HEIGHTS TO GRADUALLY RISE AS AN UPPER LEVEL
RIDGE BEGINS TO PUSH TOWARD THE PAC NW. THE ONSHORE FLOW WILL WEAKEN
AS THE LOW LEVEL FLOW TURNS MORE NORTHERLY OVER THE NEXT COUPLE OF
DAYS. THE MARINE LAYER WILL ALSO BECOME INCREASINGLY SHALLOW AS THE
HIGH PRES BUILDS IN. SO EXPECT LESS AND LESS OVERNIGHT MARINE STRATUS
INTRUSION AS WE GET LATER IN THE WEEK. IT STILL LOOKS LIKE CLOUDS
WILL FILL IN OVER A GOOD PORTION OF THE VALLEY TONIGHT AND WED
MORNING...BUT THE CLOUDS WILL BE THINNER AND THINK THAT CLOUD BURN
OFF
WILL BE QUITE A BIT SOONER THAN WE HAVE SEEN OVER THE PAST COUPLE OF
DAYS. THE INLAND PUSH LOOKS EVEN WEAKER FOR THU AND FRI
MORNINGS...AND IT CURRENTLY LOOKS LIKE MANY VALLEY LOCATIONS WILL
REMAIN STRATUS FREE. THE COMBINATION OF DECREASING CLOUD COVER AND A
GRADUALLY WARMING AIR MASS WILL RESULT IN TEMPERATURES CLIMBING
THROUGH THE REST OF THE WEEK. HIGHS SHOULD REACH WELL INTO THE 70S ON
WED AND INTO THE LOW TO MID 80S THU AND FRI. NW FLOW SHOULD KEEP
TEMPS AT THE COAST CAPPED IN THE 60S.

WILL CONTINUE WITH A SLIGHT CHANCE OF THUNDERSTORMS ALONG THE CASCADE
CREST EACH AFTERNOON AND EVENING THROUGH THE END OF THE WEEK. IT
APPEARS THAT WRAP AROUND FLOW ON THE BACK SIDE OF THE DEPARTING LOW
WILL KEEP SOME WEAK INSTABILITY OVER THE CASCADES THROUGH THU. THE
MODELS CONTINUE TO INDICATE SOME WEAK INSTABILITY FRI AS WE DEVELOP
W/SW FLOW ALOFT. PYLE

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...WEAK RIDGING OVER THE
PACNW FRIDAY NIGHT INTO SATURDAY IS PUSHED OFF TO THE EAST AS A
TROUGH OF LOW PRESSURE MOVES ONSHORE SUNDAY NIGHT. SATURDAY WILL BE
A LOT LIKE FRIDAY WITH CLOUDY SKIES EARLY CLEARING TO PARTLY CLOUDY
SKIES IN THE AFTERNOON. THERE WILL ALSO BE A SLIGHT CHANCE FOR SOME
AFTERNOON/EVENING SHOWERS OR THUNDERSTORMS NEAR THE CASCADE CREST.
WITH THE APPROACH OF THE LOW PRESSURE SYSTEM FROM THE
SOUTHWEST...EXPECT SKIES TO REMAIN MOSTLY CLOUDY TO PARTLY SUNNY ON
SUNDAY KEEPING TEMPERATURES A BIT COOLER...TOO. UNDER WESTERLY FLOW
MODELS STILL SUGGEST A SLIGHT CHANCE FOR SHOWERS OR THUNDERSTORMS IN
THE CASCADES SUNDAY AFTERNOON/EVENING. WHETHER THESE
SHOWERS/THUNDERSTORMS OCCUR WILL DEPEND ON HOW MUCH CLOUD COVER
CLEARS OUT OVER THE CASCADES BY THE AFTERNOON. SUNDAY NIGHT OR EARLY
MONDAY AS THE FRONT MOVES THROUGH ASSOCIATED WITH THE UPPER-LEVEL
LOW PRESSURE SYSTEM...MODELS SUGGEST SHOWERS WILL SPREAD ACROSS THE
AREA THROUGH THE DAY MONDAY. A CHANCE FOR SOME SCATTERED SHOWERS
BEHIND THE FRONT WILL CONTINUE THROUGH TUESDAY. -MCCOY

&&

.AVIATION...MARINE CLOUDS WORKING ITS WAY BACK TO THE COAST THIS
EVENING WITH WIDESPREAD MVFR CIGS EXPECTED. STRATUS AROUND
5000-7000 FEET ACROSS WESTERN WASHINGTON ADVANCING INTO THE
INTERIOR OF NW OREGON. BKN TO OVC CIGS GENERALLY NORTH OF KUAO.
MODELS ALL SHOW ENOUGH LOW LEVEL RELATIVE HUMIDITY TO INDICATE
MORE MARINE CLOUDS OVER MUCH OF OUR AREA TONIGHT AND WEDNESDAY
MORNING...BUT SHOULD BE SHALLOWER THAN TODAY. SO CIGS WILL BE MORE
LIKELY MVFR EXCEPT FOR POSSIBLE IFR ALONG THE COAST AND POSSIBLY
NEAR KEUG. THE LOWER INVERSION SHOULD LEAD TO EARLIER CLEARING ON
WEDNESDAY...POSSIBLY BY NOON.

KPDX AND APPROACHES...VFR CONDITIONS WITH CIGS AROUND 5000 FEET
THROUGH ABOUT 12Z WED. THEN A LOWER LAYER SHOULD FORM PROVIDED
ENOUGH CLEARING FROM THE HIGHER LAYER. ANY MVFR CIGS THAT FORM IS
EXPECTED TO DISSIPATE IN THE 18Z TO 20Z WED TIME FRAME. /MH

&&

.MARINE...NOT MUCH IN THE WAY OF SIGNIFICANT CHANGES. WILL BEGIN
TO SEE A MORE DOMINANT PAIR OF SWELL TRAINS ARRIVE FROM WELL OFF
TO THE WEST AND THE DISTANT SOUTH. ADDITIONALLY STILL HAVE SOME
FRESH SWELL FROM WINDS OFF THE WESTERN BC COAST TO COMBINE AND
PRODUCE SOMEWHAT CHOPPY AND CONFUSED SEAS. ON THE UP SIDE...
DOMINANT SEAS WILL ONLY BRIEFLY COMBINE TO AROUND 7 FT MAXIMUM AT
TIMES OVER THE NEXT COUPLE DAYS AND THUS REMAIN BELOW SMALL CRAFT
CRITERIA. OVERALL WINDS WILL STAY FROM THE WEST NORTHWEST WITH
ONLY BRIEF AND LOCALIZED GUSTS PUSHING OVER 20 KTS OVER THE FAR
SOUTHERN EXTENT OF THE WATERS. /JBONK/PT

&&

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

&&

$$

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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