FXUS66 KPQR 070426
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
825 PM PST SUN DEC  6 2009

.SYNOPSIS...A COLD UPPER TROUGH IS DROPPING SOUTH THROUGH THE PACIFIC
NORTHWEST THROUGH TONIGHT...BRINGING COLDER ARCTIC AIR AND GUSTY
NORTHEAST WINDS INTO THE AREA. ISOLATED SNOW SHOWERS ARE POSSIBLE IN
AND NEAR THE CASCADES BUT NO ACCUMULATIONS ARE EXPECTED. COLD DRY
WEATHER WILL LIKELY PERSIST THROUGH MUCH OF THE WEEK WITH
PRECIPITATION CHANCES INCREASING AGAIN THIS WEEKEND. 

&&

.SHORT TERM...NORTHEAST WINDS CONTINUE WITH GUSTS IN THE 50 TO 60 KT
RANGE AT THE HIGHER CASCADE AND COAST RANGE PEAKS AND RIDGES. IN THE
LOWER ELEVATIONS WEST OF THE CASCADES AND IN THE WESTERN GORGEWINDS
ARE MOSTLY IN THE 15 KT WITH GUSTS TO 25 KT RANGE. 

AS FOR THE INCOMING ARCTIC AIR MASS...THE COLD SURFACE AIR HAS MOVED
SOUTH TO INTERIOR SOUTHERN BRITISH COLUMBIA BUT TEMPERATURES IN
WASHINGTON AND NORTHWEST OREGON ARE STILL IN THE UPPER 20S TO LOW
30S. DEW POINTS HAVE FALLEN TO THE SINGLE DIGITS AND LOW TEENS
SHOWING THAT THE INTERIOR AIR IS ON THE WAY. WITH THE COMBINATION OF
THE CONTINUED WINDS AND COLDER AIR FILTERING IN...TEMPERATURES SHOULD
FALL RAPIDLY TONIGHT AND MONDAY MORNING AS THE THE COLDER AIR
ARRIVES. THE NORTHERLY GRADIENT DOWN THE WILLAMETTE VALLEY WILL
PERSIST OVERNIGHT WHICH WILL KEEP THE LOWER ATMOSPHERE WELL MIXED
MAKING FOR A CLEAR AND DRY BUT BRISK NIGHT. 

AS HIGH PRESSURE BUILDS OVER THE COLUMBIA RIVER BASIN TONIGHT...
WINDS IN THE GORGE WILL INCREASE SUBSTANTIALLY AS THE CROSS MOUNTAIN
EASTERLY COMPONENT OF THE PRESSURE GRADIENT STRENGTHENS. CURRENTLY
THE PRESSURE DIFFERENCE ACROSS THE CASCADES HAS INCREASED TO 3.8
MB...AND WILL INCREASE TO 5 MB BY MIDNIGHT AND 8 OR 9 MB BY EARLY
MONDAY MORNING. LOOK FOR THE SUSTAINED WESTERN GORGE EAST WINDS
INCREASING TO AROUND 30 KT LATER THIS EVENING AND TO 40 TO 45 KT BY
MONDAY MORNING. THE NORTHEASTERLY PRESSURE GRADIENT WILL CONTINUE
THROUGH THE DAY MONDAY BUT THEN TRANSITION TO A MORE STRICTLY
EASTERLY FLOW PATTERN MONDAY NIGHT AND TUESDAY. WITH CALMER MORE
STABLE CONDITIONS IN MUCH OF THE WILLAMETTE VALLEY MONDAY NIGHT AND
TUESDAY MORNING WILL LIKELY BRING THE COLDEST SURFACE TEMPERATURES TO
THE LOW LYING INVERSION PRONE AREAS. LIKENS

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...DRY CONDITIONS
PREVAIL THROUGH MID NEXT WEEK AS NW FLOW ALOFT CONTINUES OVER THE
REGION. MODELS HAVE CONTINUED TO PUSH BACK THE ARRIVAL OF THE NEXT
SYSTEM. THE TRACK OF THIS NEXT LOW WILL DETERMINE THE AMOUNT OF
PRECIP OVER THE AREA. OVERALL...BOTH GFS AND ECMWF AGREE THAT THE
NEXT SYSTEM SHOULD ARRIVE AROUND LATE FRI/EARLY SAT. PRECIP CHANCES
WILL INCREASE BY LATE FRI...WITH A POSSIBILITY OF FREEZING RAIN OR
MIXED PRECIP FOR THE EASTERN PORTION OF THE CWA ON SUN. A WEAK UPPER
RIDGE TRIES BUILDING OVER THE FORECAST AREA MON...BUT IS SQUEEZED OUT
BY A STRONG UPPER LOW EARLY TUE. LRAMIREZ

&&

.AVIATION...DRY OFFSHORE FLOW IS EXPECTED THROUGH THE NEXT 24 HOURS 
WITH VFR CONDITIONS. GUSTY EAST WINDS EXPECTED THROUGH GAPS IN 
TERRAIN.

KPDX AND APPROACHES...VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT 
24 HOURS. BRISK EASTERLY WINDS CONTINUE THROUGH LATE MON EVENING.
&&

.MARINE...STRONG OFFSHORE FLOW CONTINUES TO GENERATE EASTERLY WIND 
WAVES OVER THE WATERS...HOLDING SEAS TO NEAR 10 FT IN THE OUTER 
MARINE ZONES. WEST SWELL AROUND 3 FT AND EASTERLY WIND WAVES WILL 
RESULT IN CONFUSED SEAS...AT LEAST THROUGH EARLY NEXT WEEK. WINDS 
OVER THE WATERS ARE ABOVE SMALL CRAFT ADVISORY LEVELS...AND WILL 
DROP BELOW 20 KTS IN THE NORTHERN WATERS LATE MON AFTERNOON...THEN 
IN THE SOUTHERN WATERS MON EVENING. 

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR/WA...SMALL CRAFT ADVISORY FOR WINDS CAPE SHOALWATER TO FLORENCE 
  THROUGH MONDAY MORNING.

&&

$$

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.