FXUS66 KPQR 151002
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
200 AM PST TUE DEC 15 2009

.SYNOPSIS...A PACIFIC COLD FRONT PUSHING INTO THE REGION THIS 
MORNING WILL STALL AND WEAKEN LATER TODAY AND TONIGHT. A LOW 
PRESSURE SYSTEM LIFTING NE TOWARDS THE BRITISH COLUMBIA COAST WED 
AND THU WILL BRING A WARM FRONT INTO NW OREGON AND SW WA LATE THU. 
AN ACTIVE WEATHER PATTERN WILL CONTINUE THROUGH THE WEEKEND AS MORE 
SYSTEMS COME IN OFF THE PACIFIC.
&&

.SHORT TERM...A SERIES OF SHORTWAVES LIFTING OUT OF THE TROUGH SEEN 
ON WATER VAPOR PICTURES NEAR 150W WILL KEEP AN ABOVE NORMAL THREAT 
FOR PRECIPITATION GOING FOR THE NEXT FEW DAYS. MODELS ULTIMATELY 
STALL AND WEAKEN THE PACIFIC FRONT PUSHING INLAND EARLY THIS MORNING 
OVER THE REGION. WITH A WEAK BAROCLINIC ZONE AND THE SHORTWAVES 
CONTINUING TO MOVE ACROSS...POPS WILL GENERALLY REMAIN LIKELY OR 
ABOVE FOR THE NEXT FEW DAYS. LOW LEVEL WARM AIR ADVECTION AHEAD OF A 
WARM FRONT PROVIDES TEMPORARILY RAISES POPS WED AND WED NIGHT...BUT 
BY THU BEST ISENTROPIC LIFT HAS SHIFTED N...FOR REDUCED CHANCES FOR 
RAIN IN THE SE. 

RADAR TRENDS SUGGEST PRECIPITATION INTENSITY DROPPING OFF THROUGH 
THE GORGE AND UPPER HOOD RIVER VALLEY EARLY THIS MORNING...ALTHOUGH 
LIGHTER PRECIP IS LIKELY TO CONTINUE. EASTERLY LOW LEVEL FLOW 
THROUGH THE GORGE HAS MAINTAINED A COLD AIR MASS IN THE GORGE... 
ALTHOUGH WARM AIR IS EXPECTED BY MODELS TO OVERRUN THE COLD LOW 
LEVEL AIR THIS MORNING. OBSERVATIONS INDICATE PRETTY MUCH A RAIN TO 
SNOW TRANSITION WEST TO EAST THROUGH THE GORGE...BUT FREEZING RAIN 
SHOULD BECOME A BETTER POSSIBILITY IN THE NEXT FEW HOURS IF THE WARM 
AIR PUSHES IN OVERHEAD AS INDICATED BY MODELS. THE TREND FOR COOLING 
TEMPS IN THE WEST END OF THE GORGE APPEAR TO HAVE STABILIZED TO JUST 
ABOVE FREEZING...AS THE RAINFALL INTENSITY WEAKENED. LOW LEVEL COLD 
AIR E OF CASCADE LOCKS APPEARS LIKELY TO LINGER LONGER THAN EARLIER 
EXPECTED...SO WILL PROBABLY HAVE TO EXTEND THE GORGE ADVISORY 
THROUGH 10 AM.

SNOW CONTINUES TO FALL AT HIGH ELEVATIONS...WITH AVALANCHE CENTER 
OBSERVATIONS AROUND MT HOOD INDICATING A QUICK 6 TO 11 INCHES SINCE 
LAST EVENING. SHORT WAVE NEAR 135W IS EXPECTED TO MOVE ACROSS THIS 
AFTERNOON WJHICH MAY REINTENSIFY PRECIPITATION...BUT SNOW LEVELS 
ALSO EXPECTED TO RISE WELL ABOVE PASS LEVEL IN THE SW FLOW.

.LONG TERM...WET WEATHER PERSISTS THROUGH THE EXTENDED PERIOD. AN 
UPPER LEVEL TROUGH LEVELS A RIDGE IN PLACE OVER THE ROCKIES THU 
AFTERNOON. THIS SYSTEM IS FOLLOWED BY A SECOND FRONT CONTINUING THE 
WET TREND. BY SAT AFTERNOON...MODELS DISAGREE ON WHETHER THERE WILL 
BE A RIDGE BUILDING BEHIND THE ASSOCIATED COLD FRONT OR IF ANOTHER 
SYSTEM FALLS FROM THE NORTH TO IMPACT THE PAC NW. ECMWF SHOWS A 
BRIEF BREAK POSSIBLE BY FRI NIGHT AS THIS RIDGE AMPLIFIES. GFS 
CONTINUES WITH WET CONDITIONS IN THE FORECAST. EITHER WAY...MORE 
SLOW MOVING SYSTEMS ARE EXPECTED. HOWEVER...THEY MAY STALL AS THEY 
TRY TO CROSS THE CASCADES...WINDY CONDITIONS AND HEAVY RAIN FALL ARE 
POSSIBLE DURING THIS TIME. EXPECT SNOW LEVELS TO RISE TO NEAR 8000 
FT THROUGH THE WEEKEND AND FALLING SLOWLY THROUGH THE BEGINNING OF 
NEXT WEEK. LRAMIREZ
&&

.AVIATION...MVFR CEILINGS ACROSS THE NORTHERN HALF OF THE REGION 
THIS MORNING...WITH MOSTLY VFR CONDITIONS OVER THE SOUTHERN HALF.  
MOST AREAS WILL IMPROVE TO VFR LATER THIS MORNING. APPROACHING FRONT 
WILL SPREAD HIGH END MVFR CIGS BACK TO COAST AFTER 21Z...ALONG WITH 
INCREASING S WINDS. AFTER 00Z EXPECT THESE MVFR CONDITIONS WITH RAIN 
TO SPREAD INLAND AS FRONT PUSHES TOWARDS COAST.

.KPDX AND APPROACHES...MIX OF HIGH END MVFR AND LOW VFR...WILL 
GRADUALLY IMPROVE TO VFR BY 18Z. SHOULD REMAIN VFR FOR REST OF 
DAY...THEN RETURN OF MVFR AFTER 03Z AS RAIN INCREASES. 
&&

.MARINE...WINDS STILL IN GALE FORCE NEAR THE COAST AND ACROSS THE S 
COASTAL WATERS AND WILL REMAIN AS SUCH UNTIL 7 OR 8 AM THIS AM. 
WINDS FARTHER N HAVE SUBSIDED BELOW GALE FORCE. HOWEVER...WINDS WILL 
INCREASE AGAIN LATER TODAY AS ANOTHER FRONT ARRIVES. COMBINED SEAS 
AROUND 14 TO 20 FT THIS MORNING...MOSTLY CONSISTING OF LOCAL WIND 
GENERATED ENERGY. BASELINE SWELL AROUND 13 TO 15 FT. WIND ENERGY 
WAVES WILL EASE SOMEWHAT THIS AM...BUT EXPECT SEAS TO REMAIN AROUND 
15 FT THROUGH TONIGHT. LARGER SWELL TRAIN FROM THE N PAC WILL ARRIVE 
LATE WED AND THU...WITH 20 FT SWELLS EXPECTED. &&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR/WA...GALE WARNING ON COASTAL WATERS FROM CAPE 
         SHOALWATER TO FLORENCE UNTIL 8 AM...THEN AGAIN FOR
         LATER THIS AFTERNOON THROUGH TONIGHT. 
        SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR CONDITIONS
         THROUGH WED.
        WINTER WEATHER ADVISORY THROUGH 10 AM PST FOR
         WESTERN COLUMBIA RIVER GORGE.
        WINTER WEATHER ADVISORY THROUGH 10 AM PST FOR CASCADES
         IN LANE COUNTY-UPPER HOOD RIVER VALLEY.
        WINTER STORM WARNING THROUGH 10 AM PST FOR NORTH OREGON
         AND S WA CASCADES.
&&

$$

MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND

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.