092 
FXUS66 KPQR 221017
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR 
316 AM PDT THU OCT 22 2015

.SYNOPSIS...CLEARING SKIES BEHIND A DEPARTING FRONT WILL RESULT IN A
COOL MORNING WITH AREAS OF FOG. OFFSHORE WINDS WILL DEVELOP THIS
EVENING. CLEAR SKIES AND A DRIER ATMOSPHERE WILL LEAD TO COOLER
TEMPERATURES LATE TONIGHT WITH SOME INLAND AREAS COOLING INTO THE
30S. WEAK OFFSHORE WINDS WILL CONTINUE FRIDAY AS A LOW PRESSURE
SYSTEM APPROACHES THE PACIFIC NORTHWEST. THIS LOW WILL BRING A CHANCE
FOR RAIN LATE IN THE WEEKEND. 

&&

...FIRST FROST OF THE FALL POSSIBLE FOR THE NORMALLY COLDER
LOWLAND VALLEY LOCATIONS LATE TONIGHT/EARLY FRIDAY MORNING...

.SHORT TERM...A WEAKENING FRONT IS OVER THE CASCADES EARLY THIS
MORNING. SKIES ARE CLEARING BEHIND THE FRONT...AND EXPECT SOME
RADIATION FOG TO DEVELOP ALONG THE COAST AND IN THE INTERIOR VALLEYS
THIS MORNING...ESPECIALLY IN AREAS WHERE THE WINDS CALM. THIS FOG
WILL LIKELY BE DENSE AND LIMIT VISIBILITIES TO A QUARTER OF A MILE OR
LESS AT TIMES. DO NOT EXPECT THIS FOG TO BE WIDESPREAD OR LONG
LASTING...WITH PLENTY OF SUNSHINE THIS AFTERNOON.

A THERMAL TROUGH OVER CALIFORNIA WILL BUILD NORTHWARD INTO OREGON
THIS MORNING...WITH NORTH TO NORTHEAST WINDS HELPING MIX THE LOWER
LEVELS OF THE ATMOSPHERE. THE THERMAL TROUGH WILL REMAIN AT OR NEAR
THE COAST THROUGH EARLY FRIDAY MORNING...CONTINUING OFFSHORE WINDS.
THIS WILL HELP KEEP SKIES MOSTLY CLEAR THIS EVENING...AS WELL AS MIX
DRIER AIR ALOFT DOWN TOWARDS THE SURFACE. 

TEMPERATURES FOR THE CASCADES AND THE INTERIOR VALLEYS WILL RAPIDLY
DROP AFTER SUNSET...AND LIKELY LOWER INTO THE 30S EARLY FRIDAY
MORNING. THE OFFSHORE WINDS WILL NOT BE STRONG ENOUGH TO PREVENT
RADIATION FOG COMPLETELY...BUT THINK THE AREAL EXTENT OF FOG AND LOW
CLOUDS WILL BE MINIMAL FRIDAY MORNING. THE WILLAMETTE VALLEY
TEMPERATURES WILL BE THE COLDEST IN OUTLYING ...MORE RURAL AREAS.

THE COOL START FRIDAY SHOULD LIMIT WARMING SOMEWHAT IN THE AFTERNOON
WITH DAYTIME TEMPERATURES REMAINING NEAR SEASONAL CLIMATOLOGY. LIGHT
OFFSHORE WINDS WILL CONTINUE FRIDAY EVENING...BUT WITH MORE OF A
SOUTHERLY COMPONENT AS A CLOSED LOW APPROACHES THE COAST. THE
OFFSHORE WINDS WILL BE WEAKER...ALLOWING FOR ANOTHER OPPORTUNITY FOR
OVERNIGHT RADIATION FOG AND/OR COLD TEMPERATURES.  

WINDS WILL BECOME SOUTHERLY EARLY SATURDAY AS THE LOW NEARS THE
COAST. THE SOUTHERLY WIND REVERSAL MAY BRING SOME LOW MARINE CLOUDS
AND FOG TO THE CENTRAL OREGON COAST MID MORNING SATURDAY...MOVING
NORTH UP THE COAST THROUGH THE DAY. THE MODELS VARY ON THE TIMING OF
THE APPROACH WITH GFS THE QUICKEST SOLUTION AND THE OUTLIER. HAVE
CONTINUED TO LEAN TOWARDS THE SLOWER SOLUTIONS OF THE AM AND THE
ECMWF. SOME HIGH CLOUDS MAY BEGIN TO STREAM OVER THE AREA SATURDAY
AFTERNOON AND EVENING...BUT DO NOT EXPECT ANY RAIN FROM THE LOW UNTIL
LATER IN THE WEEKEND. TJ
  
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...A CLOSED LOW WILL
BRING A CHANCE FOR RAIN SUNDAY. THERE IS A LOT OF MODEL VARIABILITY
ON THE TIMING...AREAL EXTENT...AND AMOUNT OF RAIN. THE 00Z MODELS
FORECAST THAT THE UPPER RIDGE  WITH THE CLOSED LOW WILL
SPLIT WITH LITTLE TO NO RAIN FOR THE PORTLAND FORECAST AREA. HAVE NOT
JUMPED ONTO THIS SOLUTION QUITE YET...BUT WITH THE RECENT HISTORY OF
SPLITTING TROUGHS...THINK IT IS A REASONABLE FORECAST.	

A SHORTWAVE UPPER RIDGE SHOULD KEEP MONDAY AND TUESDAY MOSTLY
DRY....DEPENDING ON HOW THE WEEKEND UPPER TROUGH SPLITS. THIS RIDGE
WILL SLOW THE PROGRESSION OF THE NEXT SYSTEM...AND POSSIBLY EVEN
STRETCH AND SPLIT THIS SECOND UPPER TROUGH. THIS SYSTEM MAY ENTRAIN
MOISTURE FROM THE REMNANTS OF HURRICANE OLAF AND PRODUCE DECENT RAIN
SOMEWHERE ALONG THE WEST COAST. TJ 
 
&& 

.AVIATION...WIDE VARIETY OF FLYING CONDITIONS IN PLACE ACROSS THE
FORECAST AREA THIS MORNING. HIGH CLOUDS ASSOCIATED WITH A
DEPARTING COLD FRONT ARE CLEARING OUT...WHICH WILL INCREASE THE
RISK OF FOG TOWARDS SUNRISE. HOWEVER THE LOW-LEVEL AIR MASS IS
SLIGHTLY BETTER MIXED THAN WED MORNING...SO THE TENDENCY THUS FAR
HAS BEEN FOR MVFR STRATUS TO DEVELOP RATHER THAN FOG. EXPECT THIS
TREND TO CONTINUE THIS MORNING...WITH MVFR STRATUS BECOMING MORE
WIDESPREAD BY 12Z AND LINGERING THROUGH 18Z-20Z BEFORE CLEARING.
ONCE THESE CIGS CLEAR...EXPECT VFR CONDITIONS TO PREVAIL THIS
AFTERNOON AND EVENING.

VALLEYS WHICH REMAIN CLEAR THROUGH 13Z WILL HAVE AN INCREASED RISK
OF LOCALLY DENSE FOG AND LIFR CONDITIONS. GREATEST CHANCE OF FOG
THIS MORNING WILL BE IN THE WESTERN WILLAMETTE VALLEY AS WELL AS
COASTAL VALLEYS. ANY FOG SHOULD SLOWLY LIFT AFTER 16Z...WITH
CIGS/VSBYS IMPROVING TO MVFR BY 17Z THEN CLEARING TO VFR BY 20Z. 

KPDX AND APPROACHES...VFR CONDITIONS WILL LIKELY DETERIORATE TO
MVFR BY 13Z...WITH SOME PATCHY IFR POSSIBLE. THERE IS A 20 PERCENT
CHANCE OF IFR/LIFR FOG DEVELOPING IN AND AROUND KPDX THIS MORNING.
EITHER WAY...CIGS ARE EXPECTED TO CLEAR AROUND 19Z WITH VFR
THEREAFTER.  WEAGLE

&&

.MARINE...MODERATE NORTHERLY FLOW EXPECTED ACROSS THE COASTAL
WATERS TODAY WITH HIGH PRESSURE BUILDING INTO THE PAC NW AND A
THERMAL TROUGH ALONG THE S OREGON COAST. A FEW GUSTS TO 25 KT ARE
POSSIBLE FOR THE SOUTHERN WATERS...ESPECIALLY NEAR CAPES. HOWEVER
THESE ARE EXPECTED TO BE TOO LOCALIZED TO WARRANT A SCA FOR WIND.
W-NW SWELL FROM AN EARLIER GULF OF ALASKA LOW WILL ARRIVE
MIDDAY...PUSHING SEAS TO 10-12 FT AND PROMPTING A SCA FOR SEAS ALL
WATERS THIS AFTERNOON INTO TONIGHT. SEAS SHOULD FALL BACK BELOW 10
FEET FRI MORNING.

HIGH PRESSURE WILL SLOWLY WEAKEN FRI...WITH WINDS VEERING NE-E-SE
FRI-SAT AS LOW PRES NOW NEAR 155W APPROACHES THE OREGON COAST.
FORECAST MODELS CONTINUE TO SHOW A GREAT DEAL OF UNCERTAINTY AS TO
HOW STRONG THIS LOW WILL BE AS IT REACHES THE COASTAL WATERS SAT
NIGHT/SUN...PROJECTING ANYTHING FROM LIGHT SE FLOW TO NEAR-GALE
CONDITIONS. FOR NOW KEPT WINDS FAIRLY MODERATE OVER THE WEEKEND
BUT WILL NEED TO MONITOR THIS SYSTEM CLOSELY.  WEAGLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM NOON TODAY TO 
     6 AM PDT FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 11 AM 
     THIS MORNING TO 6 AM PDT FRIDAY.

&&

$$

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.