Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 042139
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
240 PM PDT FRI SEP 4 2015

.SYNOPSIS...A BROAD UPPER LEVEL LOW WILL MOVE SOUTH ACROSS WESTERN
WASHINGTON AND WESTERN OREGON TODAY...PRODUCING CONTINUED CHANCES FOR
SHOWERS AND ISOLATED THUNDERSTORMS...ESPECIALLY THIS AFTERNOON AND
EVENING. THE WEATHER WILL IMPROVE SATURDAY AS THE UPPER LOW FINALLY
BEGINS TO SLIDE EAST THOUGH SOME SHOWERS MAY LINGER IN THE HIGHER
CASCADES UNTIL LATER IN THE DAY SATURDAY. ANOTHER LOW IS THEN
EXPECTED TO MOVE INTO THE PACIFIC NORTHWEST FROM THE NORTHWEST...
WITH SOME PRECIPITATION POSSIBLE LATE SATURDAY NIGHT INTO SUNDAY
NIGHT MAINLY ACROSS SOUTHWEST WASHINGTON AND FAR NORTHWEST OREGON.
WARMER AND DRIER WEATHER IS EXPECTED TO RETURN FOR MUCH OF THE COMING
WEEK.
&&

.SHORT TERM...WITH THE AFTERNOON HEATING FOCUS FOR SHOWER ACTIVITY
SHIFTED INLAND. UPPER TROUGH AS SEEN IN WATER VAPOR PICTURES WAS
SHIFTING E ACROSS THE WILLAMETTE VALLEY EARLY THIS AFTERNOON. TROUGH
IS EXPECTED TO SHIFT E OF THE CASCADES LATE TONIGHT...WITH A
SHORTWAVE SWINGING DOWN AROUND THE WEST SIDE OF THE TROUGH LATE
TONIGHT. ISOLATED THUNDERSTORMS WERE POPPING UP WITH THE SHOWERS.
WILL KEEP SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THROUGH THE
EVENING...THEN WITH THE LOSS OF SURFACE HEATING AND UPPER TROUGH
MOVING E EXPECT ONLY LINGERING CHANCE FOR SHOWERS TO BE OVER THE
CASCADES LATE TONIGHT INTO SAT MORNING. WITH PLENTY OF BREAKS IN
CLOUDS OVERNIGHT EXPECT ANOTHER COOL NIGHT TONIGHT.

AS THE UPPER TROUGH DEPARTS FLOW TURNS NW SAT. MODELS AGREE ON A
WEAK FRONTAL SYSTEM DROPPING SW OFF THE BC COAST SAT...EVENTUALLY
MOVING INTO WESTERN WA SUN MORNING. A MOIST ONSHORE LOW LEVEL FLOW
PRECEDES THE SYSTEM...AT LEAST ACROSS THE N PART OF THE FORECAST
AREA. WILL CONTINUE TO INDICTAE THE FIRST THREAT FOR RAIN ON THE S
WA COAST AS EARLY AS SAT EVENING...THEN SPREAD POPS FURTHER INLAND
LATE SAT NIGHT AND SUN MORNING. SUPPORTING SHORTWAVE ALOFT
FOLLOWS...AND IS TO MOVE SE ACROSS WA SUN NIGHT BRINGING CHANCES FOR
RAIN TO AN END. MODELS INDICATE MODEST MOIST ISENTROPIC LIFT AROUND
290K ISENTROPE BY SUN MORNING ACROSS SW WA...SO WILL BUMP POPS UP A
BIT ACROSS THE NW CORNER OF THE FORECAST AREA THEN. DRY WEATHER TO
FOLLOW MON AS A SURFACE RIDGE OF HIGH PRES POKES IN OVER THE REGION
OFF THE PACIFIC.

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY. UPPER-LEVEL FLOW BECOMES
MORE ZONAL AS THE TROUGH WHICH HAS BEEN STATIONARY OVER OUR AREA
MOVES OFF TO THE EAST. HIGH PRESSURE BUILDS BACK OVER THE WESTERN
CONUS...WHICH WILL PUSH THE STORM TRACK TO OUR NORTH INTO WASHINGTON
AND BRITISH COLUMBIA. THIS BRINGS BACK DRY AND WARM WEATHER MORE
TYPICAL OF THIS TIME OF YEAR FOR OUR AREA. EXPECT WARMER...MORE
SEASONAL TEMPERATURES STARTING ON TUESDAY AND CONTINUING THROUGH THE
END OF THE WEEK. NORTH COAST MAY CONTINUE TO SEE SOME CLOUDS TUESDAY
THROUGH THURSDAY AS A COUPLE WEAK SYSTEMS CLIP THE NORTHERN PORTION
OF OUR AREA. OTHERWISE...THE REST OF SOUTHWEST WASHINGTON AND
NORTHWEST OREGON WILL REMAIN MOSTLY SUNNY THROUGH THE END OF NEXT
WEEK. -MCCOY
&&

.AVIATION...CONDITIONS GENERALLY VFR THROUGH THIS EVENING UNDER
SCATTERED CU. WILL CONTINUE TO SEE SCATTERED SHOWERS AND A
SLIGHT CHANCE OF ISOLATED THUNDERSTORMS THROUGH AROUND 03Z. SKIES
SHOULD ONCE AGAIN CLEAR OVERNIGHT ALLOWING THE LOWER ATMOSPHERE TO
STABILIZE. WITH LIGHT WINDS AND AMPLE LOW LEVEL MOISTURE WILL
LIKELY SEE WIDESPREAD IFR TO MVFR STRATUS REDEVELOP ACROSS THE
REGION AFTER 09Z. EXPECT ANY FLIGHT RESTRICTIONS THAT DEVELOP
TONIGHT TO IMPROVE BY LATE SUNDAY MORNING.

KPDX AND APPROACHES...VFR UNDER SCATTERED CU THROUGH THIS EVENING.
WILL CONTINUE TO SEE SCATTERED SHOWERS AND A SLIGHT CHANCE OF
THUNDERSTORMS THROUGH AROUND 03Z. CLEARING SKIES OVERNIGHT SHOULD
ALLOW WIDESPREAD IFR TO MVFR STRATUS TO REDEVELOP AFTER 10Z. /64

&&

.MARINE...HIGH PRESSURE OVER THE NORTHEAST PACIFIC AND INCREASING
LOW PRESSURE OVER THE INTERIOR WILL BRING MARGINAL SMALL CRAFT
ADVISORY WINDS TO THE WATERS...WITH GUSTS GENERALLY AROUND 20 KT.
WILL HOLD OFF ON ISSUING AN ADVISORY AS CONFIDENCE REMAINS LOW
THAT WE WILL SEE WIDESPREAD ADVISORY GUSTS ABOVE 21 KT. A WEAK
FRONT WILL MOVE ACROSS THE WATERS ON SUNDAY AND LIKELY BRING A
FEW HOURS OF SOUTHERLY WINDS...BUT IMPACTS SHOULD REMAIN MINIMAL.
THERMAL LOW PRESSURE LOOKS TO REDEVELOP OVER SOUTHERN OREGON NEXT
WEEK BRINGING A RETURN OF GUSTY NORTHERLY WINDS...ESPECIALLY TO
THE CENTRAL OREGON WATERS. A FEW WEAK DISTURBANCES MAY BRUSH THE
NORTHERN WATERS THROUGH THE WEEK...BUT MAIN IMPACT WILL BE A FEW
HOURS OF WESTERLY WINDS.

SEAS REMAIN AROUND 4 TO 6 FT THROUGH MUCH OF THE FORECAST PERIOD
AND WILL BECOME WIND DRIVEN EARLY NEXT WEEK...ESPECIALLY OVER THE
CENTRAL OREGON WATERS. SEAS MAY BUILD TOWARDS 7 FT LATE NEXT WEEK.
/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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