FXUS66 KPDT 112207
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
205 PM PST FRI DEC 11 2009
.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT. SIGNIFICANT WINTER
STORM TO IMPACT THE FORECAST AREA THIS WEEKEND. WINTER STORM
WARNINGS AND ADVISORIES ARE IN EFFECT. CURRENTLY THIS AFTERNOON
MOST OF THE REGION IS UNDER CLEAR SKIES WITH PARTLY TO MOSTLY CLOUDY
OVER CENTRAL OREGON. AS THE LOW PRESSURE SYSTEM CURRENTLY OFF THE
NORTHERN CALIFORNIA SOUTHERN OREGON COAST MOVES INLAND TONIGHT WE
WILL SEE INCREASING CLOUDS WITH LIGHT SNOW DEVELOPING. DEW POINTS
ARE LOW SO THE SNOW WILL TAKE SOME TIME TO REACH THE SURFACE. LOW
TEMPERATURES WILL BE FAIRLY COLD AGAIN TONIGHT THOUGH NOT AS COLD AS
THE PAST SEVERAL NIGHTS. THE COLUMBIA BASIN SHOULD BE THE COLDEST AS
THIS IS WHERE COLD LOW LEVEL AIR IS TRAPPED AND ALSO CLOUD COVER
WILL BE MOVING IN LATE TONIGHT. SATURDAY AND SATURDAY NIGHT WE WILL
SEE SNOW AND POSSIBLE SLEET OVER MOST OF THE FORECAST AREA. OVERALL
THE AIRMASS IS FAIRLY COLD AND SHOULD SUPPORT SNOW HOWEVER A SMALL
WARM LAYER IN THE LOWER LEVELS OF THE ATMOSPHERE COULD RESULT IN A
CHANGEOVER TO SLEET IN SOME LOCATIONS. BASED ON THE TRACK OF THE
STORM CENTER WHICH WILL BE SOUTH OF THE FORECAST AREA...EXPECT THE
LEAST AMOUNT OF PRECIPITATION OVER THE CENTRAL WASHINGTON CASCADES
INTO THE YAKIMA VALLEY. HEAVIER SNOW WILL FALL IN THE LOWER COLUMBIA
BASIN AND BLUES INTO CENTRAL OREGON. TEMPERATURES SATURDAY NIGHT
WILL BE SIGNIFICANTLY WARMER THAN PAST FEW NIGHTS DUE TO CLOUD
COVER. LOW WILL BE IN THE TEENS AND 20S. 94
.SUNDAY TROUGH MONDAY...THE WEATHER SYSTEM PASSING TO THE SOUTH WILL
STILL HAVE THE DEFORMATION BAND OF PRECIPITATION OVER SOUTHERN
WASHINGTON AND NORTHERN OREGON SUNDAY MORNING. THE NORTHERLY BRANCH
OF THE JET WILL BEGIN TO DIP SOUTH FROM BRITISH COLUMBIA RESULTING
IN A WEST TO NORTHWEST FLOW. THIS WILL FAVOR A TRANSITION TO A
UPSLOPE FLOW ALONG THE FOOTHILLS OF THE BLUE MOUNTAINS AND THE BLUE
MOUNTAINS ON SUNDAY THAT WILL LAST INTO MONDAY. MODELS ALSO SHOW A
WAVE MOVING THROUGH THIS FLOW SUNDAY NIGHT INTO MONDAY WHICH WILL
PROVIDE CONTINUAL MOISTURE AND DYNAMICS. THIS PERIOD OF TIME WILL
FAVOR SOME GOOD SNOW AMOUNTS IN THE BLUE MOUNTAINS AND FOOTHILLS.
WINTER STORM WATCH HAS BEEN ISSUED FOR THIS EVENT. COULD ALSO SEE
SOME GOOD SNOW AMOUNTS ALONG THE CREST OF THE CASCADES OF WASHINGTON
UNDER THIS FLOW. REST OF THE FORECAST AREA WILL LIKELY BE DOMINATED
BY THE CASCADE RAIN/SNOW SHADOW EFFECT WHICH WILL LIMIT
PRECIPITATION. 91
.LONG TERM...MONDAY NIGHT THROUGH FRIDAY. ANOTHER STRONG STORM
SYSTEM IS EXPECTED TO MOVE INTO THE AREA MONDAY NIGHT SPREADING
ACCUMULATING SNOW TO PORTIONS OF THE REGION INTO TUESDAY. THE
UNSETTLED WEATHER WILL PERSIST THROUGH THE WEEK AS A SERIES OF
DISTURBANCES PASS THROUGH THE TWO STATE AREA. TEMPERATURES ARE
EXPECTED TO MODERATE AND POSSIBLY CLIMB ABOVE FREEZING ACROSS MOST
PORTIONS OF THE AREA BY MIDWEEK ON A WARMER SOUTHERLY FLOW AND THIS
SHOULD RAISE SNOW LEVELS. 97
&&
.AVIATION...VFR CONDITIONS ARE LIKELY FOR ALL TAF SITES INTO PART OF
THIS EVENING. AFTER 02Z KRDM MAY EXPERIENCE MVFR/IFR CONDITIONS IN
-SN THAT WILL LOWER VSBY AND CEILINGS. AFTER 08Z KPDT...KALW...KDLS
WILL EXPERIENCE MVFR/IFR CONDITIONS AND THEN ALL TAF SITES WILL
EXPERIENCE SIMILAR CONDITIONS DUE TO LOWERING CEILINGS AND VSBY IN
SNOW AND POSSIBLY IP. 97
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 8 26 23 32 / 60 70 70 70
ALW 11 26 26 34 / 30 70 70 70
PSC 7 25 21 36 / 20 60 60 30
YKM 4 25 18 36 / 20 20 20 20
HRI 8 25 23 35 / 40 70 60 40
ELN 4 25 15 35 / 20 20 20 20
RDM 22 35 26 36 / 60 60 70 40
LGD 18 30 25 33 / 60 60 70 70
GCD 20 32 26 34 / 50 60 80 60
DLS 13 28 27 40 / 60 70 60 30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 AM PST
SUNDAY FOR ORZ041.
WINTER STORM WARNING FROM 4 AM SATURDAY TO 4 PM PST SUNDAY FOR
ORZ044-501-502.
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 10 AM PST
SUNDAY FOR ORZ503>506.
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 4 AM PST
SUNDAY FOR ORZ042-043.
WIND ADVISORY UNTIL 8 PM PST THIS EVENING FOR ORZ049.
WA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 4 AM PST
SUNDAY FOR WAZ024-502.
WINTER STORM WARNING FROM 4 AM SATURDAY TO 4 PM PST SUNDAY FOR
WAZ029-030.
WINTER WEATHER ADVISORY FROM 4 AM SATURDAY TO 10 AM PST SUNDAY
FOR WAZ028.
&&
THREAT INDEX
SATURDAY : RED
SUNDAY : YELLOW
MONDAY : YELLOW
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
$$
94/91/97/97
