Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 162152
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
245 PM PDT TUE SEP 16 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM CURRENTLY WELL OFF THE OREGON COAST
WILL MOVE TOWARDS SOUTHERN OREGON AND BRING A CHANCE OF SHOWERS LATE
WEDNESDAY INTO THURSDAY ACROSS NORTHWEST OREGON AND SOUTHWEST
WASHINGTON. ONSHORE FLOW WILL KEEP MOST OF THE SMOKE FROM THE 36
PIT AND DECEPTION COMPLEX FIRES OVER THE CASCADES AND POINTS EAST.
HOWEVER...HIGH PRESSURE AND OFFSHORE FLOW LOOKS INCREASINGLY LIKELY
TO BUILD OVER THE REGION TOWARDS THE WEEKEND SO EXPECT SMOKEY
CONDITIONS AND TEMPERATURES POSSIBLY APPROACHING 90F AGAIN ACROSS THE
WILLAMETTE VALLEY.


&&

.SHORT TERM...TONIGHT...WATER VAPOR SATELLITE IMAGERY SHOWS A LARGE
SHORTWAVE TROUGH LOCATED OFF THE CALIFORNIA COAST...PLACING THE CWA
UNDER DEEP SOUTH TO SOUTHWESTERLY FLOW ALOFT. VISIBLE SATELLITE
IMAGERY SHOWS THE FIRST ROUND OF MID TO UPPER LEVEL CLOUDS PUSHING
NORTHWARD OFF THE OREGON COAST AND ACROSS SOUTHWEST WASHINGTON.
DOPPLER RADAR INDICATES SOME LIGHT PRECIPITATION IS FALLING OUT OF
THESE CLOUDS...BUT SUSPECT THIS IS ALMOST ENTIRELY VIRGA. ANOTHER
CLUSTER OF VIRGA CURRENTLY OFF CAPE MENDOCINO SHOULD TRACK ALONG THE
OREGON COAST THIS EVENING.

THE 36 PIT AND DECEPTION COMPLEX FIRES CONTINUE TO PRODUCE PLENTY OF
SMOKE. CONTINUE TO CHECK WITH YOUR STATE AIR QUALITY AGENCY FOR THE
LATEST AIR QUALITY OBSERVATIONS. EXPECT VALLEY LOCATIONS IMMEDIATELY
DOWN RIVER OF THESE FIRES LIKE ESTACADA AND OAKRIDGE TO EXPERIENCE
PROBLEMS WITH SMOKE EACH NIGHT AND EARLY MORNING THIS WEEK.
FORTUNATELY...WEST WINDS EACH AFTERNOON AND EVENING SHOULD DISPERSE
SMOKE...ESPECIALLY WHEN THE FIRES ARE GENERALLY MOST ACTIVE....TO THE
EAST.

FOR WEDNESDAY...MODELS AGREE THE UPPER LEVEL TROUGH AND SURFACE LOW
PRESSURE CURRENTLY WELL OFF THE CALIFORNIA COAST WILL SHIFT
NORTHEASTWARD TOWARDS THE CALIFORNIA/OREGON STATE LINE THROUGH
WEDNESDAY EVENING...BEFORE SPLITTING AND NOSE DIVING INTO SOUTHERN
CALIFORNIA LATE THURSDAY. THIS RATHER MESSY PATTERN WILL RESULT IN
WAVES OF MAINLY MID TO UPPER LEVEL CLOUDS SPREADING ACROSS THE AREA
THROUGH WEDNESDAY EVENING. ASIDE FROM A FEW SPRINKLES FROM TIME TO
TIME...SUSPECT MOST LOCATIONS WILL REMAIN DRY BASED ON MODEL
SOUNDINGS. KEPT A SLIGHT CHANCE MENTION OF THUNDER ACROSS OUR
SOUTHEASTERN ZONES WEDNESDAY AFTERNOON AND EVENING WHERE PERHAPS
ENOUGH MID LEVEL INSTABILITY COULD GENERATE A LIGHTNING STRIKE OR
TWO...BUT CONFIDENCE IN THIS SCENARIO PANNING OUT IS VERY LOW.

FOR THURSDAY...THE NAM AND GFS SUGGEST A LOW LEVEL SURGE OF
ISENTROPIC LIFT AHEAD OF THE TROUGH AXIS LATE WEDNESDAY NIGHT INTO
THURSDAY MORNING MAY SATURATE THE ATMOSPHERIC COLUMN AND RESULT IN
LIGHT PRECIPITATION ACROSS MUCH OF THE AREA THURSDAY MORNING. LOW
LEVEL WESTERLY FLOW SHOULD ALSO AID IN WRINGING OUT LIGHT RAIN
ACROSS THE OROGRAPHICALLY FAVORABLE COAST RANGE AND CASCADES. AS A
RESULT...POPS WERE NUDGED UPWARDS DURING THIS PERIOD INTO THE LOW
END LIKELY CATEGORY ALONG THE COAST AND ACROSS THE TOPOGRAPHY...AND
HIGH END CHANCE CATEGORY FOR VALLEY LOCATIONS. MODELS SUGGEST CLOUD
COVER WILL BE AMPLE ON THURSDAY...BUT IF WE DO GET ANY BREAKS IN THE
CLOUDS...IT WILL NOT TAKE MUCH HEATING TO PRODUCE THUNDERSTORMS. AT
THIS POINT...CLOUD COVER LOOKS PRETTY SOLID THURSDAY SO LEFT THE
MENTION OF THUNDER OUT OF THE FORECAST...BUT THIS WILL BE WORTH
MONITORING OVER THE NEXT 48 HOURS.

OVERALL...CONTINUE TO REMAIN NERVOUS THAT MODELS ARE TOO AGGRESSIVE
WITH THE MOISTURE AND PRECIPITATION CHANCES LATE WEDNESDAY INTO
THURSDAY GIVEN THE SPLITTING NATURE OF THE UPPER LEVEL TROUGH. IN
ADDITION...THIS WILL BE THE FIRST FALL LIKE STORM SYSTEM TO TRY AND
BREAK DOWN THE LONGWAVE RIDGE...WHICH ALSO DOES NOT BODE WELL.

FOR FRIDAY...SHORTWAVE RIDGING MOVING INTO THE AREA LATE THURSDAY
INTO FRIDAY SHOULD ALLOW THE AREA TO DRY OUT CONSIDERABLY.
STRENGTHENING THERMAL LOW PRESSURE OVER CALIFORNIA ON FRIDAY WILL
TURN WINDS MORE NORTHERLY...AND THE AREA WILL BEGIN ANOTHER WARMING
TREND. /NEUMAN


.LONG TERM...SATURDAY THROUGH TUESDAY...GFS...DGEX...AND ECMWF ALL
SHOW A RETURN TO EASTERLY FLOW ON SATURDAY WHICH WILL WARM
TEMPERATURES ACROSS THE AREA. THIS WARM UP WILL ONLY LAST THROUGH
SUNDAY...AS WINDS SHIFT BACK TO THE WEST FROM AN UPPER-LEVEL TROUGH
AND ASSOCIATED CYCLONE DEEPENING OVER THE GULF OF ALASKA. THIS WILL
COOL TEMPERATURES AND BRING THE MARINE LAYER BACK IN AT NIGHT MONDAY
AND TUESDAY. -MCCOY
&&

.AVIATION...LIGHT SE WINDS HAVE HELPED CLEAR THE MARINE CLOUDS
SOONER THAN ANTICIPATED THIS AFTERNOON. MARINE STRATUS WITH MVFR
CIGS SHOULD FILL IN ALONG THE IMMEDIATE COAST AFTER 0Z. ONSHORE
WINDS ACROSS CENTRAL OREGON COAST WILL BRING SOME CLOUDS THROUGH
THE COASTAL GAPS NEAR KONP EARLY THIS EVENING...AND UP THE LOWER
COLUMBIA RIVER TOWARDS KSPB.. LIGHT SOUTH TO SOUTHEAST WINDS WILL
DEVELOP LATE TONIGHT AND PREVENT THE CLOUDS TO MOVE MUCH INLAND.
WOULD NOT BE SURPRISED IF THE MARINE CLOUDS ACTUALLY PUSH AWAY
FROM THE COAST EARLY WED MORNING. THERE MAY BE A BRIEF PERIOD OF
LOW MVFR FOR THE SOUTHERN WILLAMETTE VALLEY INCLUDING KEUG AROUND
09Z...BUT FORECAST CONFIDENCE IS LOW FOR KEUG CIGS.

SMOKE FROM THE 36 PIT WILDFIRE WILL GENERATE MVFR CIGS IN VCNTY OF
THE FIRE. THIS SMOKE SHOULD REMAIN MOSTLY OVER THE CASCADE
FOOTHILLS THIS AFTERNOON AND EVENING...BUT MAY EXPAND ITS
COVERAGE WHEN THE WINDS CALM LATE TONIGHT...AND POSSIBLY IMPACT
PARTS OF THE NORTHERN AND CENTRAL WILLAMETTE VALLEY EARLY WED
MORNING.

KPDX AND APPROACHES...VFR TODAY AND TONIGHT WITH A MIX OF HIGH
CLOUDS. TJ

&&

.MARINE...FAIRLY BENIGN CONDITIONS PERSIST OVER THE WATERS FOR
THE NEXT FEW DAYS AS WEAK LOW PRESSURE WILL MAINTAIN SOUTH WIND
GENERALLY LESS THAN 15 KT. THERE WILL BE A MIX OF WAVE TRAINS
WITH VARYING PERIODS...OUT OF THE NW...AND SW WITH THE OVERALL WAVE
HEIGHTS GRADUALLY BUILDING TONIGHT. SEA HEIGHTS OF 5 TO 7 FT CAN
BE EXPECTED THROUGH THURSDAY.

HIGH PRES WILL REBUILD OVER THE WATERS FRI AND SAT...WITH THERMAL
LOW PRESSURE OVER THE COAST AND COASTAL WATERS. THIS WILL BRING
ANOTHER ROUND OF N WINDS TO THE WATERS THIS WEEKEND WITH WINDS
POSSIBLY
REACHING SMALL CRAFT ADVISORY LEVELS AT TIMES. TJ

&&

.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 AS THE FORECAST AREA.


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