Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 211656
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
954 AM PDT SUN SEP 21 2014

.SYNOPSIS...FLOW TURNS ONSHORE TODAY AS WEAK HIGH PRESSURE BUILDS
ALONG THE COAST...FORCING A THERMAL TROUGH OF LOW PRESSURE EASTWARD
ACROSS THE CASCADES. THE MARINE LAYER IS DEEPENING ALONG THE COAST
WHICH WILL RESULT IN A CLOUDY AND MUCH COOLER DAY THERE TODAY. INLAND
AREAS WILL BE SUNNY AND A TAD COOLER...MAINLY NEAR EUGENE. SMOKE FROM
LARGE FIRES IN THE AREA WILL CONTINUE TO TINT THE SUN TODAY...
PARTICULARLY IN THE PORTLAND METRO. ONSHORE FLOW INCREASES FOR A
COOLING TREND MONDAY AND TUESDAY. AS A DYING FRONT REACHES THE COAST
THERE COULD BE A COUPLE SHOWERS COAST AND CASCADES. A MORE ORGANIZED
SYSTEM WILL BRING MORE WIDESPREAD RAIN MIDWEEK...WITH COOL AND
SHOWERY WEATHER AFTERWARDS.

&&

.UPDATE...A FEW CHANGES WERE MADE TO THE FORECAST PACKAGE THIS
MORNING...MAINLY TO BRING IT MORE IN LINE WITH MODEL CONSENSUS THAT
RAIN CHANCES MAY INCREASE A LITTLE FASTER THAN EARLIER EXPECTED FOR
THE FORECAST AREA. 12Z NAM/GFS AND 00Z ECMWF NOW HINT AT RAIN
REACHING THE PDX METRO AREA AS SOON AS TUE MORNING...FROM A DECAYING
FRONT THAT WAS PREVIOUSLY EXPECTED TO BE TOO WEAK TO BRING MUCH EAST
OF THE COAST RANGE. DID NOT EXACTLY GO WHOLE HOG JUMPING ON THIS
SOLUTION...JUST PAINTED SOME SLIGHT CHANCE POPS EASTWARD INTO THE PDX
METRO TUE MORNING. THE MORE WIDESPREAD RAIN STILL APPEARS TO HOLD OFF
UNTIL TUE NIGHT/WED...AND QPF AMOUNTS COULD BE RATHER IMPRESSIVE IF
CURRENT GUIDANCE HOLDS TRUE. ALSO OF NOTE...THE NAM 12 KM WINDS ARE
LOOKING RATHER IMPRESSIVE ALONG THE COAST WITH THE TUE NIGHT
SYSTEM...WITH 50+ KT AT 950 MB AND AS HIGH AS 60+ KT AT 850 MB ALONG
WITH THE FRONT. A LOT WILL DEPEND ON TIMING OF INDIVIDUAL WAVES
RIDING NORTHWARD ALONG THE FRONT AS IT DRIFTS ONSHORE...BUT EITHER
WAY THIS WILL PROBABLY BE THE FIRST SIGNIFICANT FALL-LIKE BLUSTERY
SOUTH WIND EVENT ALONG THE COAST...POSSIBLY ALONG WITH SOME SORT OF
COASTAL JET TUE NIGHT AS WELL.WEAGLE

/PREV DISC ISSUED 231 AM PDT SUN SEP 21 2014/

.SHORT TERM...LOW STRATUS HAS RAPIDLY SPREAD UP THE OREGON COAST
OVERNIGHT...AND CONTINUES TO PUSH UP THE WASHINGTON COAST. THERMAL
TROUGH NOW LIES FROM FAR NW WASHINGTON OVER THE WILLAPA HILLS THEN
OVER THE WILLAMETTE VALLEY. THIS IS THE LINE MARKING THE SHIFT FROM
OFFSHORE TO ONSHORE WINDS.  THIS THERMAL WILL SHIFT EAST OF THE
CASCADES BY EARLY AFTERNOON. THIS WILL ALLOW ALL WINDS TO BECOME
ONSHORE BY LATE MORNING ACROSS THE REGION. WHILE NOT ALL THAT STRONG
OVER THE INTERIOR...WILL BE ENOUGH TO HOLD TODAYS HIGHTEMPERATURES
IN THE LOWER TO MIDDLE 80S. LOW CLOUDS WILL NOT MOVE MUCH ALONG THE
COAST...KEEPING TEMPERATURES THERE IN THE LOWER TO MID 60S.

ONSHORE FLOW WILL CONTINUE TO INCREASE TONIGHT...WITH MARINE LAYER
DEEPENING AND PUSHING MARINE CLOUDS INTO THE INTERIOR. MORNING LOW
CLOUDS ON MONDAY WILL GRADUALLY BREAK UP. BUT IT WILL BE MUCH COOLER
INLAND WITH HIGHS ONLY THE 70S. AT THE SAME TIME...A FRONTAL SYSTEM
ALONG 145W WILL BE APPROACHING THE PAC NW COAST. THERE IS GOOD
AGREEMENT THAT THIS SYSTEM WILL STRETCH APART WHILE APPROACHING THE
COAST...WITH THE BULK OF LEFTOVER ENERGY HEADED TOWARD BRITISH
COLUMBIA. THE FRONT MAY HOLD TOGETHER LONG ENOUGH FOR SPOTTY LIGHT
RAIN ALONG THE WASHINGTON AND N OREGON COAST.

WILL ALSO KEEP MINOR THREAT OF SHOWERS OVER THE HIGH CASCADES OF
OREGON FOR MONDAY. THIS DUE TO MOISTURE ROTATING UP OUT OF NEVADA
INTO SOUTHERN OREGON. SINCE SO CLOSE TO THE MOISTURE POOL...CAN NOT
RULE OUT A SHOWER OR TWO.

ANOTHER FRONT WILL APPROACH LATER TUESDAY...AND WILL BE A BIT
STRONGER. SO SEEMS TUESDAY WILL BE A REPEAT OF MONDAY...BUT THREAT OF
MOISTURE PUSHES FURTHER INLAND INTO THE COAST RANGES. HAVE INCREASED
CLOUD COVER...AND PUT THREAT OF OCCASIONAL SPRINKLES OVER INTERIOR
FOR TUE.     ROCKEY.

.LONG TERM...FIRST SIGNIFICANT FRONT OF THE FALL SEASON ARRIVES LATE
TUE NIGHT AND WED. VERY WELL COULD SEE AROUND 1 INCH OF RAIN IN THE
COAST RANGES...AND WIDESPREAD 0.33 TO 0.50 INCH ACROSS INLAND AREAS.
FRONT IS ARRIVING IN A SOUTH TO NORTH ORIENTATION. AS A RESULT...IT
WILL BE SLOWING ITS EASTWARD PROGRESSION INTO THE PAC NW. SO RAINFALL
HAS POTENTIAL TO BE A BIT HEAVIER OVER THE WEST SLOPES OF THE COAST
AND CASCADES RANGES. WILL BE PLENTY OF CLOUDS AND MUCH COOLER FOR
WED. AFTER THAT FRONT CLEARS THE REGION WED EVENING... AIR MASS WILL
REMAIN UNSETTLED WITH SHOWERS AND COOL WEATHER. SUCH COOL DAMP
WEATHER WILL GO FAR IN QUIETING WILDFIRE ACTIVITY. ROCKEY.
&&

.AVIATION...VFR CONDITIONS PERSIST INLAND THROUGH THIS EVENING.
MARINE STRATUS WILL THEN FILL THE VALLEY WITH LOW MVFR CIGS BY
MONDAY MORNING. AT THE COAST...IFR TO LIFR CIGS WITH OCCASIONAL
VISIBILITY RESTRICTION IN FOG CONTINUE TODAY. CIGS ARE EXPECTED TO
RISE TONIGHT TO 1000-1500 FT RANGE AS AN UPPER TROUGH APPROACHES
THE REGION.

KPDX AND APPROACHES...VFR CONDITIONS THROUGH 09Z MON THEN
INCREASING CHANCES FOR LOW MVFR CIGS. LOW MVFR CIGS LIKELY BY 12Z
MON.

&&

.MARINE...SOUTHERLY WINDS HAVE SPREAD ACROSS THE WATERS EARLIER
THIS MORNING OVERNIGHT AS THE COASTAL TROUGH SPREAD INTO
WASHINGTON. WINDS WILL INCREASE A BIT THROUGH THIS
AFTERNOON...AND SMALL CRAFT ADVISORY FOR WINDS REMAINS IN EFFECT
FOR THE NORTHERN ZONES WITH THE STRONGEST WINDS ARE EXPECTED OUT
TO ABOUT 40 NM THROUGH THIS AFTERNOON. WINDS WILL EASE ACROSS ALL
WATERS THIS EVENING. THE NEXT WEAKENING FRONT FOR MONDAY AFTERNOON
MAY BRING ANOTHER ROUND OF SMALL CRAFT ADVISORY WINDS...BEFORE A
FAIRLY STRONG LOW PRES SYSTEM MOVES TOWARDS THE WATERS ON TUE
THROUGH THU WITH A BETTER CHANCE FOR ADVISORIES NEEDED FOR THIS
SYSTEM.

WESTERLY SWELL 6 FT THROUGH THIS MORNING...THEN SLOWLY SUBSIDING
THROUGH THE EARLY PART OF THE WEEK. COMBINED SEAS THEN LIKELY
BUILD WED INTO THE 10-15 FT RANGE WITH APPROACHING LOW PRES SYSTEM.
SEAS MAY REMAIN AROUND 10 FT THROUGH FRI...BUT MODEL DIFFERENCES
AFTER THU INCREASE UNCERTAINTY FOR THE END OF THE WEEK.  CULLEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 PM PDT THIS AFTERNOON
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT
     60 NM.

&&

$$

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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