Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 061018
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
317 AM PDT WED MAY  6 2015

.SYNOPSIS...A COOL UPPER LOW PRES AREA OVER WASHINGTON WILL SLOWLY
SINK SOUTHWARD TODAY AND THU. THIS WILL BRING SHOWERY WEATHER TO THE
REGION TODAY AND TONIGHT. ONCE LOW SHIFTS FURTHER SOUTHEAST INTO THE
GREAT BASIN ON THU. THIS WILL ALLOW HIGH PRES TO BUILD OVER PAC
NW...WITH DRIER WEATHER AND WARM TEMPERATURES FOR THU THROUGH SUN.
&&

.SHORT TERM...TONIGHT THROUGH FRIDAY...
COOL UPPER LOW NOW CENTERED OVER CENTRAL WASHINGTON...WITH SPOKES OF
UPPER LEVEL ENERGY ROTATING AROUND THE LOW FROM VANCOUVER ISLAND
SOUTHWARD INTO WESTERN WASHINGTON AND OREGON. FIRST SPOKE NOW
BRINGING SHOWERS TO MUCH OF NW OREGON AS OF 2 AM. THESE SHOWERS ARE
NOT ALL THE INTENSE...BUT CAN EXPECT A BRIEF DOWNPOUR FROM TIME TO
TIME.

AS THE UPPER LOW DRIFT SOUTHWARD ACROSS WASHINGTON AND INTO CENTRAL
OREGON...THE COOLEST AIR ALOFT WILL ALSO DROP SOUTHWARD. AIR MASS
ALOFT WILL COOL A LOT MORE THIS AM AS COMPARED TO YESTERDAY...WITH
TEMPERATURES AT 500 MB...OR ABOUT 25K FT...RUNNING AT -25 TO -30 DEG
BY LATE MORNING. THIS WILL ALLOW FOR MORE BUBBLY CLOUDS AND THUS
BETTER BUOYANCY ALOFT...RESULTING IN MORE ORGANIZED SHOWERS AND EVEN
A FEW THUNDERSTORMS. BEST INSTABILITY WILL BE EAST OF THE COAST RANGE
AND PRIMARILY FROM LATE MORNING THROUGH EARLY EVENING. THIS
SAID...SHOWERS WILL STILL REMAIN SCATTERED IN NATURE. ANY OF THE
HEAVIER SHOWERS AND THUNDERSTORMS WILL PRODUCE SMALL HAIL.

SHOWERS WILL BE DECREASING LATER THIS EVENING AND OVERNIGHT AS THE
UPPER LOW CONTINUES ITS DIVE SOUTHWARD. BY THU AM...THE LOW WILL HAVE
PUSHED INTO NE CALIF. WITH THE COUNTER-CLOCKWISE MOTION ALOFT AROUND
THE LOW...MOISTURE AND INSTABILITY WILL PUSH INTO THE SE HALF OF
OREGON AND UP AGAINST THE E SLOPES OF THE SOUTH AND CENTRAL OREGON
CASCADES. WILL KEEP MINOR THREAT OF SHOWERS FOR CASCADES S OF SANTIAM
PASS FOR THU AM. BUT I SUSPECT THAT MAY STILL BE OVERDONE AND INSTEAD
MAY JUST HAVE SOME SCRAWNY CUMULUS BUILDUPS.  THREAT OF SHOWERS ENDS
THU AFTERNOON AS LOW WILL PULL TOO FAR TO THE SOUTH.

ONCE THE LOW DEPARTS...HIGH PRES WILL BE BUILDING OFFSHORE. THIS WILL
BRING BACK A DRY NORTHERLY FLOW TO W WASHINGTON AND NW OREGON. SO
AFTER SOME MORNING CLOUDS...WILL SEE PLENTY OF SUNSHINE ON THU AND
FRI. WITH COOL AIR MASS AND LIGHT WINDS...TEMPERATURES TONIGHT WILL
DROP INTO THE 40S...AND POSSIBLY AS COOL AS THE MIDDLE 30S IN MORE
RURAL LOCATIONS. THIS WILL BOOST POTENTIAL OF PATCHY FROST
TONIGHT...ESPECIALLY IN HOOD RIVER VALLEY AND MORE RURAL AREAS OF
WILLAMETTE VALLEY AND CLARK COUNTY. BUT THIS WILL DEPEND ON WHETHER
OR NOT THE WINDS GO CALM AND SKIES CLEAR. WILL HAVE DAY SHIFT
RE-EVALUATE THIS POTENTIAL. AFTER A COOL START TO THU...TEMPERATURES
WILL QUICKLY WARM. INLAND TEMPERATURES WARM BACK INTO THE LOWER 70S
ON THU...THEN THE UPPER 70S ON FRI. THIS SUPPORTED BY VARIOUS MODELS
WHICH HAVE 850 MB TEMPS JUMPING SOME 5 TO 8 DEG FROM THU TO FRI. EVEN
COASTAL AREAS WILL WARM BUT STILL ONLY IN THE 60S.  ROCKEY.

.LONG TERM...FRIDAY NIGHT THROUGH MONDAY. AN UPPER LEVEL RIDGE WILL
DOMINATE FRIDAY AND SATURDAY FOR DRY AND WARM WEATHER. INLAND
TEMPERATURES WILL WARM TO THE UPPER 70S FRIDAY AND SATURDAY. GUSTY
NORTH WINDS ALONG THE COAST WILL KEEP COASTAL TEMPERATURES IN THE LOW
60S. SUNDAY WILL BE SLIGHTLY COOLER AS AN UPPER LEVEL TROUGH
APPROACHES. A WEAK COLD FRONT MAY BRING SOME LIGHT RAIN SUNDAY NIGHT
AND MONDAY MORNING. AN UPPER LOW WILL MOVE OVER THE AREA MONDAY
CONTINUING THE THREAT FOR SHOWERS. THE UPPER TROUGH/LOW WILL RESULT
IN COOLER TEMPERATURES MONDAY AND TUESDAY WITH HIGHS IN THE 60S AND
LOWS IN THE MID 40S. TJ
&&

.AVIATION...EXPECT MOSTLY VFR TODAY AND TONIGHT AS THE UPPER
LEVEL LOW CONTINUES TO SLOWLY MOVE ACROSS THE REGION. SCATTERED
SHOWERS CONTINUE TO MOVE ONSHORE THIS MORNING AS A WEAK SHORTWAVE
MOVES INLAND. INCREASED SHOWER ACTIVITY AND ISOLATED THUNDERSTORMS
POSSIBLE AFTER 18Z TODAY FOR INLAND TAF SITES...WITH BRIEF
PERIODS OF REDUCED CIGS AND VSBY UNDER HEAVER SHOWERS THROUGH
THIS EVENING.

KPDX AND APPROACHES...MOSTLY VFR TODAY AND TONIGHT. SCATTERED
SHOWERS TO CONTINUE THROUGH THIS EVENING. SHOWER ACTIVITY
INCREASES THIS AFTERNOON WITH ISOLATED THUNDERSTORMS POSSIBLE
AFTER 18Z TODAY.
&&

.MARINE...THE UPPER LEVEL LOW WILL CONTINUE TO SLOWLY MOVE ACROSS
THE REGION TODAY. EXPECT AN OCCASIONAL SHOWER THIS MORNING...WITH
GUSTS TO 25 KT POSSIBLE UNDER HEAVIER SHOWERS. OTHERWISE...WINDS
LOOK TO REMAIN BELOW ADVISORY CRITERIA TODAY AND TONIGHT. HIGH
PRES LOOKS TO REBUILD OVER THE NE PAC ON THU...WITH THERMAL LOW
PRES BUILDING OVER THE S OREGON COAST. EXPECT A GUSTY NORTHERLY
WIND PATTERN THROUGH THE WEEKEND WITH GUSTS TO 30 KT POSSIBLE.
THE STRONGEST WINDS WILL BE SOUTH OF TILLAMOOK. A WEAK SYSTEM
LOOKS TO APPROACH THE REGION EARLY NEXT WEEK...BUT IMPACTS SHOULD
BE MINIMAL.

SEAS WILL RANGE BETWEEN 5 TO 8 FT THROUGH EARLY NEXT WEEK.
HOWEVER...PERIODS OF STEEP AND CHOPPY SEAS ARE POSSIBLE THROUGH
THIS WEEKEND WITH THE GUSTY NORTHERLY WINDS.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
CONDITIONS FROM 5 AM TO 9 AM TODAY.
&&


$$

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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