FXUS66 KPQR 071100
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
259 AM PST MON DEC  7 2009

.SYNOPSIS...A COLD UPPER TROUGH WILL SLOWLY DROP SOUTH OF THE REGION
TODAY. A MODIFIED ARCTIC AIR MASS WILL CONTINUE THROUGH TUESDAY WHILE
GUSTY NORTHEAST WINDS SLOWLY TAPER OFF. COLD DRY WEATHER WILL PERSIST
THROUGH MUCH OF THE WEEK WITH PRECIPITATION CHANCES INCREASING AGAIN
THIS WEEKEND. 

&&

.SHORT TERM...GUSTY NORTHEAST WINDS WILL CONTINUE ACROSS THE REGION
THIS MORNING AS DEEP E-NE FLOW CONTINUES ON THE N SIDE OF A COLD
UPPER TROUGH WHICH EXTENDS FROM CENTRAL ID TO NW CA. THE WINDS ARE
NOT PARTICULARLY IMPRESSIVE WITH MOST GUSTS BELOW 25-35 KT. EVEN THE
HIGHER CASCADE WINDS HAVE DROPPED OFF OVERNIGHT. EXPECT THE WINDS TO
CONTINUE DECREASING THIS AFTERNOON AND TONIGHT AS THE UPPER TROUGH
DROPS FURTHER TO THE SE DECREASING THE FLOW ALOFT ACROSS THE REGION.
THE EXCEPTION AREA OF COURSE IS THE WESTERN GORGE WHERE THE COLD LOW
LEVEL AIR MASS STACKED UP OVER THE COLUMBIA BASIN AND E SLOPES WILL
MAINTAIN A MODERATE GRADIENT THROUGH THE GORGE THROUGH TUE MORNING. 

AS FOR THE INCOMING ARCTIC AIR MASS...THE BULK OF THE COLDEST AIR
REMAINS BOTTLED UP IN CANADA. HOWEVER AN EXTENSION OF THE COLD
SURFACE HIGH PRES WILL CONTINUE TO BUILD OVER THE COLUMBIA BASIN
THROUGH TONIGHT...FEEDING COLD BUT DRY AIR INTO THE FORECAST AREA.
THE NE PRES GRADIENT WILL CONTINUE TODAY BUT THEN TRANSITION TO A
MORE STRICTLY EASTERLY FLOW PATTERN TONIGHT AND TUE. THE CALMER MORE
STABLE CONDITIONS IN MUCH OF THE WILLAMETTE VALLEY TONIGHT AND
TUE MORNING WILL LIKELY BRING THE COLDEST SURFACE TEMPERATURES TO
THE LOW LYING INVERSION PRONE AREAS. HIGH RESOLUTION NAM12 AND WRFGFS
GUIDANCE SHOWS THE OFFSHORE FLOW WEAKENING TUE AFTERNOON AND TUE
NIGHT...THEN BECOMING NEUTRAL BY WED AFTERNOON. THIS SEEMS UNLIKELY
WITH A COLD LOW LEVEL AIR MASS REMAINING TRAPPED OVER THE COLUMBIA
BASIN. HOWEVER A WEAKER OFFSHORE FLOW SHOULD ALLOW FOR SLIGHTLY
WARMER DAYTIME TEMPERATURES. RW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...DRY CONDITIONS
PREVAIL THROUGH MID 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 WILL CONTINUE THROUGH TUE MORNING. 

&&

.MARINE...STRONG OFFSHORE FLOW CONTINUES TO GENERATE EASTERLY WIND 
WAVES OVER THE WATERS...HOLDING SEAS TO AROUND 9 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. SMALL 
CRAFT ADVISORY WINDS WILL EASE TO BELOW ADVISORY LEVELS BY MIDDAY 
TODAY.

&&

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

&&

$$

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.