Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 272158 RRA
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
258 PM PDT WED MAY 27 2015


.SYNOPSIS...THE UPPER LEVEL CLOSED LOW THAT HAS BEEN OVER THE PAC NW
FOR THE PAST FEW DAYS IS NOW CENTERED OVER WRN IDAHO. THE LOW WILL
CONTINUE TO PUSH GRADUALLY EASTWARD INTO THE NRN ROCKIES TONIGHT AND
THU. AN UPPER LEVEL RIDGE WILL BUILD IN BEHIND...BRINGING A WARMER
AND DRIER AIR MASS FOR THE REST OF THE WEEK AND MUCH OF THE WEEKEND.
ANOTHER UPPER LEVEL LOW WILL APPROACH FROM THE SW LATE LATE SUN INTO
MON...BRINGING COOLER TEMPS AND A THREAT FOR SHOWERS AND
THUNDERSTORMS FOR EARLY NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...THE PERSISTENT CLOSED UPPER
LEVEL LOW THAT HAS BEEN OVER THE PAC NW FOR THE PAST SEVERAL DAYS IS
NOW CENTERED OVER WRN IDAHO THIS AFTERNOON. SIMILAR TO
YESTERDAY...AFTERNOON SHOWERS AND THUNDERSTORMS ARE DEVELOPING UNDER
THE COLD LOW OVER ERN WASHINGTON AND OREGON. A FEW SHOWERS ARE
DEVELOPING ALONG THE E SLOPES OF THE SOUTH WASHINGTON CASCADES...SO
WILL CONTINUE TO KEEP A SLIGHT CHANCE OF THUNDER ALONG THE CREST
THROUGH EARLY THIS EVENING. HOWEVER...MOST OF THE ACTIVITY SHOULD
AGAIN REMAIN EAST OF THE CREST. OTHERWISE...A VERY NICE DAY IS
UNDERWAY ACROSS THE FCST AREA. THE THINNER MARINE STRATUS LAYER TODAY
BURNED OFF QUITE A BIT SOONER THAN WE SAW THE PAST COUPLE OF
DAYS...ALTHOUGH SOME STRATOCUMULUS HAVE FORMED OVER THE PAST COUPLE
OF HOURS DUE TO DAYTIME LOW LEVEL MIXING. EXPECT AFTERNOON HIGHS TO
REACH INTO THE MID TO UPPER 70S FOR MOST EVERYONE IN THE INTERIOR
LOWLANDS...WHILE THE COAST WILL REMAIN IN THE 60S WITH NORTHWESTERLY
ONSHORE FLOW.

THE UPPER LOW WILL DRIFT FURTHER EAST TONIGHT AND THU. THIS WILL
ALLOW AN UPPER LEVEL RIDGE TO PUSH TOWARD THE PAC NW...BRINGING A
GRADUALLY WARMER AND DRIER AIR MASS TO THE REGION. EXPECT THE MARINE
STRATUS TO PUSH TO BE EVEN WEAKER TONIGHT...WITH THE MAJORITY OF
INLAND VALLEY LOCATIONS REMAINING CLOUD FREE. 850 MB TEMPS ARE
EXPECTED TO INCREASE TO 13 TO 15 C TOMORROW...WHICH SHOULD RESULT IN
AFTER HIGHS REACHING INTO THE 80S FOR MOST OF THE INTERIOR LOWLANDS.
THE COAST WILL AGAIN STAY COOLER WITH THE NW LOW LEVEL FLOW.

THE WARM WEATHER WILL CONTINUE FOR FRI AND SAT AS THE UPPER RIDGE
MOVES THROUGH THE REGION. HOWEVER...THE RIDGE WILL BE FLATTENED OUT
SOMEWHAT BY A LOW MOVING IN TO THE NORTH OVER B.C. A WEAK SHORTWAVE
ASSOCIATED WITH THE LOW MAY MOVE BRING SLIGHTLY MORE ONSHORE FLOW ON
FRI...BUT EXPECT MINIMAL IMPACT TO THE SENSIBLE WEATHER. TEMPS ON FRI
AND SAT SHOULD BE SIMILAR TO THU WITH INTERIOR HIGHS INTO THE LOW TO
MID 80S.

WILL CONTINUE TO KEEP A SLIGHT CHANCE OF THUNDER ALONG THE CASCADE
CREST EACH AFTERNOON AND EVENING FOR THE NEXT FEW DAYS...AS THE
MODELS CONTINUE TO ADVERTISE SOME LINGERING INSTABILITY. THE BEST
CHANCE APPEARS TO BE ON FRI AS THE WEAK UPPER LEVEL SHORTWAVE MOVES
THROUGH. PYLE

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...WEAK SHORTWAVE
RIDGING MOVES THROUGH THE AREA EARLY SAT NIGHT WITH AN APPROACHING
UPPER LEVEL LOW PRESSURE SYSTEM NEARING 130W BY EARLY SUN. AS THIS
LOW PRESSURE TRACKS INLAND...INCREASING CLOUDS AND MUCH COOLER
TEMPERATURES MOVE INTO THE REGION. SHOWERS WILL BEGIN BY LATE SUN
AFTERNOON OR EVENING AS THE SURFACE BOUNDARY SLIDES ONSHORE AND
ACROSS THE REGION...WITH A CHANCE FOR THUNDERSTORMS IN THE CASCADES
SOUTH OF AROUND MT HOOD. AS THIS UPPER LOW CONTINUES TO TRACK ALONG
A GENERALLY SOUTHWEST TO EAST-NORTHEAST PATH ACROSS THE REGION AND
THEN EAST OF THE CASCADES...EXPECT CONTINUED RAIN CHANCES AND COOLER
WEATHER TO CONTINUE THROUGH AROUND MIDWEEK. WHILE SOME MODEST
DIFFERENCES IN PATTERN EVOLUTION BETWEEN MODEL SOLUTIONS SUGGEST A
BIT OF UNCERTAINTY IN LOCATION AND TIMING OF RAINFALL AMOUNTS...THE
MODEL GUIDANCE REMAINS IN REMARKABLY DECENT AGREEMENT WITH RESPECT
TO THE SHOWERY PATTERN ALONG WITH TEMPERATURES AT OR A FEW DEGREES
BELOW SEASONAL NORMALS.
&&

.AVIATION...THE SUMMERTIME STRATUS PATTERN LOOKS TO CONTINUE FOR
THE NEXT SEVERAL DAYS. A MIXTURE OF CIGS CURRENTLY EXISTS ALONG
THE COAST. EXPECT THESE CIGS TO CONTINUE TO THIN AND LIFT THIS
AFTERNOON WITH MOSTLY VFR CIGS THROUGH AROUND 03Z. VFR CIGS
CONTINUE INLAND WITH SCATTERED CUMULUS DEVELOPING OVER THE HIGHER
TERRAIN. EXPECT VFR CONDITIONS TO CONTINUE INTO TONIGHT WITH
SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE ALONG THE CASCADES.
MVFR STRATUS LIKELY RETURNS TO THE COAST THIS EVENING...WITH IFR
CIGS AND VSBY POSSIBLE EARLY THU MORNING. MVFR STRATUS LOOKS TO
PUSH INLAND THU MORNING. CONDITIONS THU LOOK TO BE A CARBON COPY
OF TODAY.

KPDX AND APPROACHES...EXPECT VFR CONDITIONS WITH SCATTERED SHOWERS
AND THUNDERSTORMS POSSIBLE ALONG THE CASCADES THROUGH 04Z. MVFR
STRATUS LOOKS TO RETURN AFTER 14Z THU MORNING. /64

&&

.MARINE...MILD CONDITIONS CONTINUE THROUGH THE WEEKEND WITH HIGH
PRES OFFSHORE AND LOW PRES OVER THE INLAND PAC NW. EXPECT NW WINDS
TO REMAIN GENERALLY BELOW SMALL CRAFT ADVISORY CRITERIA.
HOWEVER...BRIEF PERIODS OF ISOLATED GUSTS ABOVE 21 KT ARE POSSIBLE
SOUTH OF NEWPORT IN THE AFTERNOON/EVENING. MIXED SEAS BETWEEN 5
AND 7 FT WILL CONTINUE THROUGH THE WEEKEND AND COULD BECOME CHOPPY
AT TIMES DUE TO THE FRESH NW SWELL BEING GENERATED OFF OF B.C. THE
SW SWELL IS EXPECTED TO BECOME THE DOMINATE SWELL ON FRI. /64

&&

.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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