Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 021009
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
301 AM PDT TUE SEP  2 2014

.SYNOPSIS...AFTER MORNING CLOUDS BREAKUP...AN INCOMING FRONT WILL
BRING INCREASING CLOUDS AND A CHANCE FOR LIGHT RAIN SHOWERS TO MAINLY
SOUTHWEST WASHINGTON AND EXTREME NORTHWEST OREGON LATE THIS AFTERNOON
AND EVENING. MORNING CLOUDS SHOULD ONCE AGAIN RETURN WEDNESDAY...AND
RESULT IN ONE LAST DAY WITH TEMPERATURES NEAR TO SLIGHTLY BELOW
NORMAL. STRENGTHENING OFFSHORE WINDS WILL ALLOW TEMPERATURES TO RISE
INTO THE UPPER 80S AND LOW 90S FOR MANY INTERIOR LOCATIONS LATE IN
THE WORK WEEK. THERE IS A CHANCE ANOTHER STORM SYSTEM COULD BRING A
CHANCE FOR LIGHT RAIN SHOWERS TO THE AREA EARLY NEXT WEEK.

&&

.SHORT TERM...TODAY THROUGH FRIDAY...FOG PRODUCT AND SURFACE
OBSERVATIONS EARLY THIS MORNING INDICATE FOG IS SKIRTING THE CENTRAL
OREGON COASTLINE. IN ADDITION...LOW CLOUDS ARE BEGINNING TO DEVELOP
AROUND THE CASCADE FOOTHILLS NEAR TROUTDALE AND ARE IN THE PROCESS OF
RAPIDLY EXPANDING. CURRENTLY HAVE LOW CONFIDENCE IN THE MORNING CLOUD
FORECAST SO WILL LIKELY UPDATE THE FORECAST DEPENDING ON CLOUD
TRENDS. WHAT CLOUDS DEVELOP INLAND THIS MORNING SHOULD TEMPORARILY
BREAK UP TOWARDS MIDDAY.

WATER VAPOR SATELLITE IMAGERY REVEALS A COMPACT SHORTWAVE TROUGH
NEAR THE QUEEN CHARLOTTE ISLANDS EARLY THIS MORNING. THIS SYSTEM
WILL SLIDE SOUTHEASTWARD ACROSS WASHINGTON TODAY. A TRAILING FRONT
WILL SLIDE SOUTHEASTWARD ACROSS THE NORTHERN HALF OF THE AREA THIS
AFTERNOON AND EVENING...RESULTING IN A FEW LIGHT SHOWERS ACROSS
SOUTHWEST WASHINGTON...AND THE WEST FACING SLOPES OF THE NORTH
OREGON CASCADES AND COAST RANGE. POPS WERE BUMPED UPWARDS...BUT QPF
STILL LOOKS MEAGER.

THE AFOREMENTIONED FRONT WILL PUSH SURFACE HIGH PRESSURE
SOUTHWARD...AND INTO A POSITION THAT SHOULD ALLOW MARINE CLOUDS TO
DEVELOP ACROSS MUCH OF NORTHWEST OREGON TUESDAY NIGHT INTO WEDNESDAY
MORNING. THIS SHOULD RESULT IN ONE LAST DAY OF NEAR TO SLIGHTLY BELOW
NORMAL TEMPERATURES WEDNESDAY.

STRENGTHENING HIGH PRESSURE OVER THE NORTHEAST PACIFIC AND WEAK UPPER
LEVEL TROUGHING OVER SOUTHWEST OREGON AND NORTHERN CALIFORNIA...WILL
TURN MID LEVEL WINDS MORE NORTHEASTERLY OVER THE AREA. THIS WILL
ALLOW THERMAL LOW PRESSURE CURRENTLY OVER NORTHERN CALIFORNIA TO
BUILD UP THE COAST LATE WEDNESDAY INTO THURSDAY. THIS SHOULD RESULT
IN TEMPERATURES RISING INTO AT LEAST THE UPPER 80S AND LOW 90S FOR
THE WILLAMETTE VALLEY COME FRIDAY AND SATURDAY. IN ADDITION...POOR
NIGHT TIME RELATIVE HUMIDITY RECOVERIES AND MODEST EAST WINDS ACROSS
THE CASCADES AND COAST RANGE WILL ENHANCE FIRE WX CONCERNS. THE
MENTION OF SMOKE WAS ALSO ADDED TO THE FORECAST ACROSS MUCH OF LANE
COUNTY DUE TO THE PROXIMITY OF THE DECEPTION FIRE COMPLEX. /NEUMAN


.LONG TERM...SATURDAY THROUGH MONDAY...NO CHANGES...PREVIOUS
DISCUSSION FOLLOWS....A WEAK...POSITIVELY-TILTED TROUGH WILL MOVE
THROUGH OUR AREA LATE THIS WEEK.  NOT ONLY IS MOISTURE LIMITED FOR
THE PASSAGE OF THIS SYSTEM...BUT ANY PRECIPITATION THAT DOES DEVELOP
SHOULD BE EAST OF THE CASCADE RIDGE...OUTSIDE OF OUR AREA.  LATE THIS
WEEKEND THE GFS...ECMWF...AND DGEX ALL ARE SUGGESTING A LONGWAVE
TROUGH WILL MOVE ONSHORE BRINGING A CHANCE FOR SOME RAINFALL SUNDAY
NIGHT OR MONDAY. DISAGREEMENT BETWEEN MODELS ON TIMING AND BECAUSE OF
HOW FAR OUT THIS SYSTEM IS IN THE FORECAST PERIOD...THERE IS A LOT OF
UNCERTAINTY WITH THIS SYSTEM. KEPT POPS THE SAME AS THEY CAPTURE THIS
UNCERTAINTY WELL. -MCCOY

&&

.AVIATION...TAIL END OF A WEAK COLD FRONT IS MOVING THROUGH THE
FORECAST AREA EARLY THIS MORNING...MIXING OUT THE MARINE LAYER
THAT HAD BEEN PRODUCING IFR/LIFR CONDITIONS ALONG THE COAST. IT
APPEARS THERE IS A LITTLE BIT MORE MOISTURE BEHIND THE FRONT...AND
THE GENERAL ONSHORE FLOW PATTERN WILL INCREASE THROUGHOUT THE
MORNING. THIS IS ALREADY BEGINNING TO SHOW IN THE FORMATION OF A
LOW MVFR CLOUD DECK NEAR KTTD. SUSPECT THIS CLOUD DECK WILL EXPAND
OVER THE COMING HOURS AND CIGS AROUND 1500 FT WILL BE COMMON IN THE
NORTHERN WILLAMETTE VALLEY BY SUNRISE...INCLUDING THE PDX METRO
AND POSSIBLY AS FAR S AS KSLE. WITH DECENT ONSHORE FLOW IT MAY
TAKE SOME TIME FOR LOW CLOUDS TO BURN OFF ACROSS THE PDX METRO...
POSSIBLY AS LATE AS 20Z...AND EVEN THEN IT MAY JUST TURN INTO A
SCT-BKN STRATOCUMULUS LAYER AROUND 3000 FT. LOW CLOUDS WILL
LIKELY FILL BACK IN ALONG THE COAST THIS MORNING AS WELL...WITH
IFR OR LOW MVFR CIGS EXPECTED MUCH OF THE DAY AND EVEN SOME -RA
POSSIBLE NEAR KAST AROUND 00Z AS THE NEXT WEAK COLD FRONT MOVES
ACROSS WASHINGTON.  WEAGLE

KPDX AND APPROACHES...VFR CONDITIONS THIS EVENING. STRATUS
DEVELOPING AROUND 10Z WITH MVFR CIGS LIKELY THROUGH 19-20Z. THIS
LIKELY LIFTS INTO A SCT-BKN VFR STRATOCUMULUS DECK AROUND 3500 FT
FOR THE AFTERNOON. SLIGHT CHANCE OF A SHOWER AFTER 01Z WITH MVFR
CIGS RE-FORMING DURING THE EVENING.  WEAGLE/SCHNEIDER

&&

.MARINE...POST FRONTAL N-NW WINDS REMAIN BELOW SMALL CRAFT
ADVISORY CRITERIA ACROSS OUR WATERS THIS MORNING...WITH A COUPLE
GUSTS UPWARDS OF 20 KT. WINDS LIKELY EASE AND BACK LATER TODAY AS
NEXT WEAK COLD FRONT APPROACHES. THIS FRONT WILL MOVE ACROSS OUR
WATERS THIS AFTERNOON AND EARLY EVENING...BUT WILL BE WEAKENING AS
IT DOES SO. FRONT MAY REMAIN STRONG ENOUGH TO PRODUCE SOME S-SW
GUSTS 15-20 KT ALONG THE S WA COAST AS IT MOVES ONSHORE. WINDS
SHIFT TO N-NW AGAIN BEHIND THE FRONT WITH A FEW GUSTS TO 20 KT BUT
AGAIN REMAIN BELOW SCA CRITERIA. N-NW WINDS WILL INCREASE WED/THU
AS HIGH PRESSURE STRENGTHENS OFFSHORE AND THERMAL TROUGH OF LOW
PRESSURE EXTENDS NORTHWARD FROM CALIFORNIA. GUSTS 20-25 KT APPEAR
LIKELY ALONG THE CENTRAL OREGON COASTAL WATERS AS EARLY AS WED
AFTERNOON...THEN THROUGHOUT OUR WATERS THURSDAY. SEAS MAY APPROACH
10 FT IN THE S WA COASTAL WATERS WED DUE TO SOME NW SWELL
ASSOCIATED WITH TODAYS FRONTAL SYSTEM COMBINING WITH WIND WAVES.
SEAS SHOULD EASILY REMAIN BELOW 10 FT FARTHER SOUTH...THOUGH WILL
LIKELY BE CHOPPY WED/THU AS N-NW WINDS INCREASE WITH THE THERMAL
TROUGH. LIGHTER WINDS/SEAS APPEAR LIKELY FRI/SAT AS HIGH PRESSURE
WEAKENS OFFSHORE.  WEAGLE

&&

.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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