FXUS66 KPQR 061705
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
904 AM PST SUN DEC 6 2009
.SYNOPSIS...A COLD UPPER TROUGH WILL DROP SOUTH THROUGH THE PACIFIC
NORTHWEST TODAY...BRINGING COLDER ARCTIC AIR AND GUSTY NORTHEAST
WINDS INTO THE AREA TODAY THROUGH MONDAY. ISOLATED SNOW SHOWERS ARE
POSSIBLE TODAY BUT NO ACCUMULATIONS ARE EXPECTED. COLD WEATHER WILL
LIKELY PERSIST THROUGH THE FIRST HALF OF THE WEEK.
&&
.SHORT TERM...THE RADAR IS SHOWING SOME INTERESTING BANDED STRUCTURES
THIS MORNING. THE BRIGHTER ECHOES ARE ANCHORED TO THE VOLCANOES AND
MOST LIKELY SNOW BLOWING OFF THE PEAKS IN THE STRONG NORTHEASTERLY
WINDS PUSHING INTO THE AREA. WEAKER TRANSIENT ECHOS MOVING THROUGH
THE PATTERN INDICATE SNOW FLURRIES AND AREAS OF LIGHT SNOW. SO FAR
REPORTED SNOW ACCUMULATIONS HAVE BEEN QUITE SPOTTY AND LITTLE MORE
THAN A DUSTING...BUT STILL ENOUGH TO MAKE SOME TO THE LESS TRAVELED
ROADS QUITE SLIPPERY IN PLACES.
NORTHEAST WINDS CONTINUE TO INCREASE WITH GUSTS IN THE 50 TO 60 KT
RANGE AT THE HIGHER CASCADE AND COAST RANGE PEAKS AND RIDGES. EAST OF
THE CASCADES IN THE COLUMBIA RIVER BASIN NORTHEASTERLY WINDS ARE ALSO
QUITE IMPRESSIVE WITH 30 TO 40 KT WINDS IN PLACES THAT ONLY SELDOM
PICK UP MUCH WIND DURING OFFSHORE FLOW. NOT SURE IF I HAVE EVER SEEN
STRONGER NE WINDS AT ROOSEVELT THAN ROOSTER ROCK BEFORE BUT THAT
SEEMS TO BE THE EFFECT OF THE LARGE NORTHERLY COMPONENT TO THE
NORTHEASTERLY GRADIENT. SO FAR IN THE LOWER ELEVATIONS WEST OF THE
CASCADES AND IN THE WESTERN GORGE SUSTAINED WINDS ARE IN THE 15 TO 25
KT RANGE WITH GUSTS OF 30 TO 35 KT. SITES WITH BOTH NORTHERLY AND
EASTERLY EXPOSURE ARE REPORTING THE HIGHEST GUSTS THIS MORNING WHICH
IS BRINGING BREEZY CONDITIONS TO A MUCH MORE WIDESPREAD AREA THAN THE
TYPICAL EAST WIND EVENT. WHILE THE FOOT PRINT OF THE EVENT IS LARGER
THAN NORMAL THE LACK OF AN INVERSION AT RIDGE LEVEL SHOULD KEEP THE
WINDS FROM CONCENTRATING INTO A STRONGER DOWNSLOPE WIND EVENT ALONG
THE WEST SLOPES.
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 DID FALL MORE DRAMATICALLY OVERNIGHT TO THE SINGLE
DIGITS AND LOW TEENS SHOWING THAT THE INTERIOR AIR IS ON THE WAY.
WITH THE COMBINATION OF THE CONTINUE WINDS AND COLDER AIR FILTERING
IN TODAY TEMPERATURES SHOULD STAY WITHIN A FEW DEGREES OF THEIR
PRESENT VALUE THROUGH THIS AFTERNOON THEN FALL MORE 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 IS 2 TO 3 MB WHICH WILL
INCREASE TO AROUND 5 MB THIS AFTERNOON AND 8 OR 9 MB BY EARLY MONDAY
MORNING. LOOK FOR THE SUSTAINED WESTERN GORGE EAST WINDS INCREASING
TO AROUND 30 KT 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. RUTHFORD
.LONG TERM...DRY CONDITIONS EXPECTED THROUGH MUCH OF THE WEEK AS NW
FLOW ALOFT CONTINUES OVER THE NW STATES. EXPECT SOME OFFSHORE FLOW TO
CONTINUE BUT NO REINFORCING DISTURBANCES ARE SHOWN IN CURRENT MODELS
WHICH COULD TIGHTEN OFFSHORE PRESSURE GRADIENTS. PRECIP CHANCES WILL
INCREASE A LITTLE BY LATER IN THE WEEK...BUT THE MAIN THREAT FOR
RENEWED PRECIP WILL BEGIN SOMETIME NEXT WEEKEND. BEFORE THEN WEATHER
SYSTEM IN THE WESTERLIES WILL BE MAKING LANDFALL WELL TO
OUR S. RW
&&
.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 DEVELOP THIS MORNING AS OFFSHORE
GRADIENTS INCREASE.
&&
.MARINE...STRONG OFFSHORE FLOW WILL GENERATE EASTERLY WIND
WAVES...BRINGING SEAS TO NEAR 10 FT IN THE OUTER MARINE ZONES BY
THIS AFTERNOON. WEST SWELL AROUND 3 FT AND EASTERLY WIND WAVES WILL
RESULT IN CONFUSED SEAS...AT LEAST THROUGH EARLY NEXT WEEK. WINDS
WILL INCREASE TO LOW END GALES BY LATER THIS MORNING...ESPECIALLY
WEST OF GAPS IN COASTAL TERRAIN AND FURTHER OFF SHORE.WINDS WILL
EASE TO SMALL CRAFT ADVISORY LEVELS AGAIN BY MON MORNING.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR/WA...GALE WARNING 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.
