FXUS66 KPDT 160605 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PENDLETON OR
1005 PM PST TUE DEC 15 2009
UPDATED AVIATION DISCUSSION AND WARNINGS/ADVISORIES SECTION
.SHORT TERM...UPDATE...COMPLEX...MESSY PATTERN CONTINUES. A WARM
FRONT MOVED THROUGH THIS AFTERNOON. AS A RESULT SNOW LEVELS ARE
RISING ACROSS EASTERN OREGON AND ARE BEGINNING TO SLOWLY RISE IN
EASTERN WASHINGTON. MODIFIED ARCTIC AIR REMAINS TRAPPED IN THE
COLUMBIA BASIN. THE TOP OF THIS AIR MASS SEEMS TO BE AROUND 1300 FT
MSL ON THE EAST SIDE OF THE BASIN AND NEAR 2000 FT MSL ON THE WEST
SIDE. THUS...WITH SNOW LEVELS RISING THERE HAS BEEN FREEZING RAIN IN
MANY PLACES WITHIN THIS AIR MASS. THE THREAT OF MORE FREEZING RAIN
REMAINS WITH THE PASSAGE LATER TONIGHT OF THE NEXT GOOD BAND OF
PRECIPITATION. AS SUCH HAVE CONTINUED THE FREEZING RAIN ADVISORY IN
THE COLUMBIA RIVER GORGE...THOUGH SURFACE TEMPS ARE A PATCHWORK OF
ABOVE AND BELOW 32 DEGREES. CURRENTLY HAVE AN ICE STORM WARNING UP
FOR THE LOWER COLUMBIA BASIN IN OREGON AND WASHINGTON UNTIL 10 PM.
THIS WILL MOST LIKELY BE EXTENDED THROUGH THE REMAINDER OF TONIGHT
AS TEMPS CONTINUE TO SIT AT OR JUST BELOW 32 DEGREES. AREAS ON THE
FRINGE OF THIS COLD AIR MASS MAY SEE BRIEF TEMP DROPS AS THE AIR
MASS SLOSHES AROUND. SNOW FALL SHOULD BE LIMITED TO ABOUT AN INCH IN
THE YAKIMA AND KITTITAS VALLEYS TONIGHT AND HAVE LOWERED THE WINTER
STORM WARNINGS IN THESE ZONES. SOME SHOWERS OF FREEZING RAIN CAN BE
EXPECTED IN THESE VALLEYS THOUGH AS THE SNOW LEVELS HAVE RISEN SOME
OVER THEM. SNOW LEVELS CONTINUE TO RISE IN THE BLUE MOUNTAINS AND
SHOULD TOP OUT AT 4500 FEET TONIGHT. AS SUCH HAVE LOWERED THE
ADVISORY IN THE SOUTHERN OREGON BLUE MOUNTAINS DUE TO THE SNOW
LEVELS BEING ABOVE THE PASSES AND THE MAIN POPULATION AREAS IN THAT
ZONE. OTHERWISE HAVE EITHER EXTENDED OR CONTINUED ALL OTHER
ADVISORIES AND WARNINGS THROUGH TONIGHT TO ACCOMMODATE THE NEXT BAND
OF PRECIP. 90
.LONG TERM...PREVIOUS DISCUSSION...THURSDAY THROUGH SATURDAY
NIGHT...MODELS ARE IN RELATIVELY GOOD AGREEMENT WITH ANOTHER WEATHER
SYSTEM MOVING INTO THE REGION THURSDAY NIGHT. THIS WILL BRING A
CHANCE OF PRECIPITATION TO THE REGION WITH SNOW ABOVE 3000 FEET. A
SECOND DISTURBANCE WILL APPROACH THE SOUTHERN OREGON AND NORTHERN
CALIFORNIA COAST ON FRIDAY AND PUSH INTO THE REGION OVERNIGHT AND
INTO SATURDAY. THIS WILL BRING ANOTHER CHANCE OF PRECIPITATION TO
THE REGION. MODELS START TO DISAGREE BEHIND THIS SYSTEM WITH THE GFS
BRINGING A TROUGH WITH COLDER AIR INTO THE REGION SATURDAY
NIGHT...WHILE THE EUROPEAN STRENGTHENS THE RIDGE OFF SHORE. HAVE
LOWERED PRECIPITATION CHANCES SATURDAY NIGHT AS BOTH MODELS INDICATE
A DECREASE IN THE THREAT FOR PRECIPITATION...BUT HAVE KEPT
TEMPERATURES NEAR NORMAL DUE TO THE UNCERTAINTY IN THE MODELS.
SUNDAY THROUGH TUESDAY...AN UPPER LEVEL RIDGE WILL MOVE OVER EASTERN
WASHINGTON AND OREGON SUNDAY WITH DRY CONDITIONS EXCEPT NEAR THE
CASCADES. SUNDAY NIGHT THROUGH TUESDAY A SERIES OF DISTURBANCES
ROTATING AROUND AN UPPER LEVEL LOW OFF THE COAST WILL MOVE OVER THE
PACIFIC NORTHWEST...KEEPING A CHANCE OF PRECIPITATION OVER EASTERN
WASHINGTON AND OREGON. MODEL TIMING HAS BEEN INCONSISTENT AND
ENSEMBLE SPREAD IS HIGH. THIS GIVES A LOW CONFIDENCE IN TIMING AND
STRENGTH...SO KEPT A BROAD BRUSH CHANCE MOUNTAINS AND SLIGHT CHANCE
VALLEYS THROUGH THE PERIOD.
&&
.AVIATION...06Z TAFS...A WEATHER DISTURBANCE CONTINUES TO SPREAD
RAIN OR FREEZING RAIN ACROSS NORTHEAST OREGON AND SOUTHEAST
WASHINGTON THIS EVENING. THE BEST CONDITIONS SHOULD BE AT KRDM AND
KPDT WHERE SOUTH AND SOUTHEAST FLOW RESPECTIVELY WILL KEEP CIGS AND
VIS MAINLY VFR. A BAND OF RAIN MAY BRIEFLY LOWER CIGS/VIS TO MVFR
EARLY WEDNESDAY MORNING...ESPECIALLY AT KPDT. THERE IS SLIM
POTENTIAL THAT WEST FLOW COULD BRIEFLY REAPPEAR AT KPDT AS THE
PRECIP BAND MOVES THROUGH. THIS WOULD PUSH THE COLD AIR MASS TRAPPED
AT LOWER ELEVATIONS INTO KPDT FOR POSSIBLE LOWER CIGS AND VIS. AT
THIS TIME THE DOWNSLOPE GRADIENTS ALONG THE BLUE MOUNTAIN FOOTHILLS
ARE STRONG AND WILL NOT INDICATE THIS POTENTIAL IN THE TAFS. KPSC...
KYKM...KDLS AND KALW ARE IN OR VERY NEAR THE COLD AIR POOL AND
THEREFORE EXPECT PRIMARILY MVFR CONDITIONS ELSEWHERE...WITH ONLY
BRIEF BREAKS. KPSC AND KYKM REMAIN WELL WITHIN THIS AIR MASS AND
WILL SEE FREEZING RAIN AT TIMES. KALW...BEING ON THE FRINGE OF THE
COLD AIR MASS...HAS THE POTENTIAL OF SEEING ALMOST ANY CIG...VIS AND
PRECIP COMBINATION...THEREFORE FORECAST CONFIDENCE IS LOW. 90
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 34 41 32 41 / 80 50 50 20
ALW 31 42 35 42 / 80 50 50 20
PSC 30 40 32 41 / 80 30 30 20
YKM 27 36 29 37 / 50 40 40 20
HRI 31 41 32 41 / 80 40 40 20
ELN 27 35 28 37 / 50 50 60 30
RDM 33 45 30 45 / 60 40 50 30
LGD 35 39 30 40 / 60 60 50 20
GCD 35 40 30 42 / 60 40 40 20
DLS 32 41 33 42 / 80 60 70 30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...ICE STORM WARNING UNTIL 5 AM PST WEDNESDAY FOR ORZ044.
WINTER STORM WARNING UNTIL 10 AM PST WEDNESDAY FOR ORZ502.
FREEZING RAIN ADVISORY UNTIL 4 AM PST WEDNESDAY FOR ORZ041.
WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY FOR ORZ050.
WA...ICE STORM WARNING UNTIL 5 AM PST WEDNESDAY FOR WAZ028.
FREEZING RAIN ADVISORY UNTIL 4 AM PST WEDNESDAY FOR WAZ024.
WINTER STORM WARNING UNTIL 4 AM PST WEDNESDAY FOR WAZ501-502.
WINTER WEATHER ADVISORY UNTIL 10 AM PST WEDNESDAY FOR WAZ030.
&&
THREAT INDEX
WEDNESDAY : YELLOW
THURSDAY : GREEN
FRIDAY : GREEN
GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
$$
90/84/90
