Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 262136
AFDPQR

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

.SYNOPSIS...AN UPPER LEVEL LOW PRES SYSTEM CENTERED OVER EASTERN WA
TODAY 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...A SLOW MOVING CLOSED UPPER
LEVEL LOW IS CENTERED NEAR SPOKANE WASHINGTON THIS AFTERNOON.
NUMEROUS SHOWERS AND THUNDERSTORMS HAVE DEVELOPED TODAY UNDER THE
ASSOCIATED COLD POOL ALOFT OVER E WASHINGTON AND FAR NW OREGON. BASED
ON THE LATEST NWS DOPPLER RADAR IMAGERY...THERE ARE NOW
SOME SHOWERS FORMING ALONG THE EASTERN SLOPES OF THE S WASHINGTON
CASCADES. WILL HOLD ON TO A SLIGHT CHANCE FOR THUNDER ALONG THE S
WASH CASCADE CREST IN OUR FCST AREA...ALTHOUGH THINK THAT MOST
OF THE ACTIVITY WILL CONTINUE TO REMAIN ON THE E SLOPES.
ELSEWHERE...MARINE STRATUS CLOUDS HAVE STEADILY DISSIPATED THROUGH
THE DAY. THIS TREND SHOULD CONTINUE THROUGH THE REST OF THE
AFTERNOON...WITH MOST EVERYONE SEEING SOME SUNSHINE BY THE TIME THE
DAY IS OVER.

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 ARE TRYING TO THIN EARLY THIS AFTERNOON
BUT STILL HANGING TOUGH...ESPECIALLY IN THE EASTERN VALLEYS AND
WEST SLOPES OF THE CASCADES. EXPECT THE CLOUDS TO CONTINUE TO THIN
AND CLEAR TO A LARGE DEGREE THROUGH THE LATTER HALF OF THE AFTERNOON
AND EARLY EVENING. STILL QUITE A BIT OF CLOUDS TO THE NORTH AROUND
PUGET SOUND SO STILL MORE CLOUDS TO ADVECT SOUTH INTO OUR AREA
OVERNIGHT AND WEDNESDAY MORNING. THE MODELS ALL SHOW ENOUGH LOW
LEVEL RELATIVE HUMIDITY TO INDICATE MORE MARINE CLOUDS OVER MUCH
OF OUR AREA TONIGHT AND WEDNESDAY MORNING. THE MODELS ALSO
SUGGEST THAT THE MARINE INVERSION WILL BE LOWERING DURING THE NEXT
24 HOURS...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...CIGS AROUND 040 SHOULD BECOME SCATTERED
IN THE 2 TO 4 PM TIME FRAME. EXPECT CIGS TO RETURN LATE EVENING
OR AROUND MIDNIGHT...BECOMING MAINLY MVFR CIGS THROUGH MOST OF
WEDNESDAY MORNING. EARLIER CLEARING EXPECTED WEDNESDAY...POSSIBLY
BY NOON. PT

&&

.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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