FXUS66 KPDT 111744 AAA
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
940 AM PST FRI DEC 11 2009
UPDATED AVIATION DISCUSSION
.SHORT TERM...MAINLY CLEAR SKIES ACROSS THE FORECAST AREA THIS
MORNING. SATELLITE SHOWING HIGH CLOUDS MOVING IN FROM THE NORTH AND
SOUTH SO CLOUD COVER SHOULD BE SLOWLY INCREASING DURING THE DAY. A
NARROW BAND OF FOG IS PRESENT ALONG THE COLUMBIA RIVER WHICH WILL
DISSIPATE OVER THE NEXT FEW HOURS. TEMPERATURES ARE STILL PRETTY
COLD THIS MORNING THOUGH SOME WARMING IS NOTED AT MOST LOCATIONS AS
SOUTHERLY FLOW ALOFT IS WARMING THE AIRMASS. MAIN CONCERN CONTINUES
TO BE THE APPROACHING STORM AND THE WINTER MIX OF PRECIPITATION IT
WILL BRING TO THE REGION STARTING TONIGHT AND LASTING THROUGH THE
WEEKEND. NEW MODEL RUNS CONTINUE THE TREND OF SPREADING SNOW INTO
THE AREA TONIGHT FROM SOUTH TO NORTH. 94
.AVIATION...OCCASIONAL MVFR/IFR CONDITIONS ARE POSSIBLE AT TAF SITE
KDLS DUE TO LOWERING CEILINGS AND POSSIBLE LOWERING VSBY UNTIL 20Z.
OTHERWISE VFR CONDITIONS ARE LIKELY FOR ALL TAF SITES INTO THIS
AFTERNOON. AFTER 22Z 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 IP.
&&
.PREV DISCUSSION... /ISSUED 325 AM PST FRI DEC 11 2009/
SHORT TERM...TODAY THROUGH SATURDAY...TODAY WILL BE DRY FOR MOST OF
THE FORECAST AREA AS WE WILL STILL BE BETWEEN THE NORTHERN JET
STREAM AND AND ASSOCIATED MID/UPPER LEVEL LOW OVER WESTERN CANADA
AND THE SOUTHERN JET STREAM MAKING LANDFALL IN SOUTHERN CALIFORNIA.
LOOK FOR INCREASING CLOUDS THIS AFTERNOON IN CENTRAL OREGON AS
MOISTURE ADVANCES INTO OREGON FROM THE SOUTHERN JET STREAM. WATER
VAPOR IMAGERY LOOP SHOWS A DISTURBANCE RIDING ALONG THE SOUTHERN JET
STREAM NEAR 46N/155W...WHICH WILL MOVE EASTWARD TODAY AND APPROACH
THE NORTHERN CALIFORNIA COAST TONIGHT AND SPREAD MOISTURE ACROSS THE
OREGON PORTION OF THE FORECAST AREA INTO FAR SOUTHERN AND SOUTHEAST
WASHINGTON OVERNIGHT. WITH A VERY COLD AIR MASS IN PLACE...WARM AIR
OVERRUNNING TONIGHT WILL PRODUCE SNOW EAST OF THE OREGON CASCADES
WITH SNOW MOVING INTO THE EASTERN COLUMBIA GORGE TOWARD MIDNIGHT
WITH SNOW CONTINUING IN THE GORGE THOUGH SATURDAY. A WARM LAYER
ALOFT WILL PRODUCE A WINTERY MIX OF SNOW AND SLEET IN CENTRAL AND
NORTH CENTRAL OREGON WITH A CHANCE OF FREEZING RAIN AT LOWER
ELEVATIONS TONIGHT. A DEFORMATION ZONE SETS UP OVER EXTREME NORTHERN
OREGON ON SATURDAY AS THE NORTHERN JET STREAM DIPS SOUTHWARD INTO
THE PACIFIC NORTHWEST THUS ENHANCING DYNAMIC LIFT IN THE FOOTHILLS
OF THE BLUE MOUNTAINS FOR A DECENT SNOW EVENT THERE ON SATURDAY.
POLAN
LONG TERM...SATURDAY NIGHT THROUGH THURSDAY. THE ACTIVE WEATHER
WILL CONTINUE THROUGH THE LONG TERM PERIOD. THE VARIOUS WINTER
STORM WATCHES AND ADVISORIES ARE IN EFFECT THROUGH SUNDAY MORNING.
ON SATURDAY NIGHT AND SUNDAY...A STATIONARY BAND WILL BRING STEADY
SNOW TO AREAS SOUTH AND EAST OF THE TRI-CITIES, WASHINGTON. A WATCH
WILL BE ISSUED FOR THE BLUE MTN FOOTHILLS WHERE CONFIDENCE IS FAIRLY
HIGH THAT THIS AREA WILL SEE HEAVY SNOW. ACCUMULATIONS IN THE LOWER
COLUMBIA BASIN NEAR THE WA/OR BORDER AS WELL AS THE NORTHERN BLUE
MTNS MAY REACH ADVISORY CRITERIA BUT WILL LET THE DAY SHIFT TAKE A
CLOSER LOOK TO DETERMINE IF WARNING AMOUNTS WILL BE MET. THE NAM
MAY BE TOO BULLISH WITH PRECIPITATION AMOUNTS...SO WILL SEE WHAT 12Z
RUNS HAVE IN STORE. THE WINTER HIGHLIGHTS MAY NEED TO BE EXTENDED
THROUGH SUNDAY NIGHT AND MONDAY AS WELL FOR AREAS ALONG THE WA/OR
BORDER...AS THE STATIONARY FRONT MAY LINGER EVEN LONGER DESPITE THE
UPPER LEVEL TROUGH EXITING THE REGION. A WEAK TRANSITORY RIDGE WILL
MOVE EAST OF THE CASCADES MONDAY FOR A BRIEF BREAK IN PRECIPITATION
BEFORE THE NEXT SYSTEM ARRIVES MONDAY NIGHT AND TUESDAY. THIS
SYSTEM HAS A DECENT MOISTURE TAP OFF THE PACIFIC...SO PRECIPITATION
AMOUNTS COULD BE SIGNIFICANT AND MORE WINTER HIGHLIGHTS MAY BE
NEEDED. THE FORECAST AREA WILL REMAIN UNDER A MOIST W-SW FLOW ALOFT
THROUGH THE END OF THE WEEK FOR CONTINUED PERIODS OF SNOW.
TEMPERATURES WILL GRADUALLY WARM...SO THE BASIN AND SURROUNDING
VALLEYS MAY BEGIN TO SEE PRECIPITATION CHANGING FROM SNOW OR WINTER
MIX EARLY IN THE WEEK TO ALL RAIN BY WEDNESDAY. JOHNSON
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 25 16 30 26 / 0 60 70 70
ALW 23 19 29 26 / 0 30 80 70
PSC 25 15 29 22 / 0 20 50 40
YKM 24 13 30 20 / 0 0 20 20
HRI 24 14 31 23 / 0 40 60 50
ELN 29 12 27 17 / 0 0 20 20
RDM 35 21 35 26 / 10 60 50 60
LGD 27 20 31 25 / 0 60 60 70
GCD 33 23 33 28 / 0 60 50 70
DLS 30 18 32 27 / 0 60 60 60
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER STORM WATCH FROM THIS EVENING THROUGH LATE SATURDAY NIGHT
FOR ORZ041.
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 4 AM PST
SUNDAY FOR ORZ042-043.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
ORZ501.
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM PST
SUNDAY FOR ORZ504>506.
WIND ADVISORY UNTIL 8 PM PST THIS EVENING FOR ORZ049.
WA...WINTER STORM WATCH FROM THIS EVENING THROUGH LATE SATURDAY NIGHT
FOR WAZ024-502.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR
WAZ029.
&&
THREAT INDEX
TODAY : YELLOW
SATURDAY : RED
SUNDAY : 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/
