FXUS66 KPDT 151048
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
250 AM PST TUE DEC 15 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY. A MOIST PACIFIC WARM FRONT IS
BRINGING WIDESPREAD PRECIPITATION EAST OF THE CASCADES WITH MULTIPLE
WINTER STORM WARNINGS AND WINTER WX ADVISORIES IN EFFECT. BOTH THE
YAKIMA VALLEY AND THE EASTERN COLUMBIA RIVER GORGE WERE RECENTLY
UPGRADED FROM AN ADVISORY TO A WARNING AS HEAVY SNOW ACCUMULATED
SEVERAL INCHES IN A SHORT PERIOD OF TIME. ALL OTHER WARNINGS AND
ADVISORIES APPEAR ON TRACK. THE WARM AIR HAS SPREAD ACROSS EASTERN
OREGON AND SE WASHINGTON. IN CENTRAL OREGON...SNOW LEVELS APPEAR TO
BE AROUND 4500 FEET BASED ON LATEST OBS. THE WARM AIR HAS OVERRIDDEN
THE COLD AIR IN THE BASIN...AND WIDESPREAD FREEZING RAIN HAS BEEN
OBSERVED. THERE ARE SIGNS THAT THE COLD AIR IS SCOURING OUT ALONG
THE BASE OF THE BLUE MTNS WHERE S-SE WINDS ARE INCREASING AND TEMPS
ARE WARMING INTO THE MID 30S TO LOWER 40S. IT WILL GRADUALLY WARM
THIS MORNING TO OTHER AREAS ALONG THE BLUE MTN FOOTHILLS...AND IN
THE AFTERNOON FOR THE LOWER COLUMBIA BASIN SOUTH OF THE TRI-CITIES.
HEAVY SNOW IS CURRENTLY FALLING IN THE NORTHERN BLUE MTNS...BUT
INCREASING SNOW LEVEL WILL ALLOW PCPN TO CHANGE TO RAIN THIS
AFTERNOON FOR ELEVATIONS BELOW 4500 FEET. WINDS IN THE SOUTHERN
GRANDE RONDE VALLEY ARE VERY WINDY AND AREAS OF BLOWING SNOW IS
EXPECTED. THIS IS COVERED IN THE WINTER WX ADVISORY.
A MOIST SW FLOW ALOFT WILL REMAIN OVER THE AREA TONIGHT AND
WEDNESDAY. WHILE THE COLD AIR REMAINS TRAPPED ALONG THE EAST SLOPES
OF THE CENTRAL WA CASCADES (AND POSSIBLY THE KITTITAS VALLEY), THE
REMAINDER OF THE REGION WILL SEE PCPN MAINLY AS RAIN BY WEDNESDAY.
THERE ARE NO ORGANIZED FRONTAL SYSTEMS EXPECTED ON WEDNESDAY...SO
THE BEST CHANCE FOR PRECIPITATION WILL BE OVER THE CASCADES AND
EASTERN MTNS. JOHNSON
.LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY...AN OVERALL FAST
PROGRESSIVE WEATHER PATTERN WILL CONTINUE INTO THE EXTENDED FORECAST
PERIOD AND PERSIST THROUGH THE REST OF THIS WEEK AND CONTINUE INTO
EARLY NEXT WEEK. WEAK SHORTWAVE RIDGES BETWEEN EACH WEATHER SYSTEM
WILL BRING A SHORT BREAK IN THE ACTION...HOWEVER OVERALL CONDITIONS
WILL REMAIN MOIST AND SHOWERY. SNOW LEVELS ARE EXPECTED TO BE FAIRLY
HIGH THROUGH THE PERIOD SO MOST LOCATIONS WILL RECEIVE MAINLY
RAIN...INCLUDING THE PASSES. THE RAIN WILL LIKELY MIX WITH AND
CHANGE TO SNOW DURING THE NIGHT TIME HOURS AT TIMES IN THE MOUNTAINS
AND OVER THE PASSES SO THEREFORE THE PASSES WILL NOT BE COMPLETELY
SNOW FREE. IN THE LOWER ELEVATIONS SHOWERY CONDITIONS WILL PERSIST
WITH NEAR NORMAL TEMPERATURES. HOWEVER THERE MAY BE WET SNOW OR
POCKETS OF FREEZING RAIN IN THE COLDER VALLEYS SUCH AS THE YAKIMA
AND KITTITAS VALLEYS DURING THE NIGHT TIME HOURS AS TEMPERATURES DIP
TO NEAR FREEZING OR SLIGHTLY BELOW. 88
&&
.AVIATION...PREVIOUS DISCUSSION 06Z TAFS...SNOW SHOWERS CONTINUE
ACROSS THE YAKIMA AND KITTITAS VALLEY. SNOW ACCUMULATIONS AT KYKM
ARE ABOUT AN INCH PER HOUR AND SHOW NO SIGNS OF LETTING UP BEFORE
10Z. SNOW SHOWERS WILL PICK UP ACROSS KPSC...KALW...AND KPDT ANYTIME
AFTER 06Z. EXPECT FREQUENT CHANGES IN FLIGHT CONDITIONS FROM MVFR TO
IFR OVER THE NEXT 18 TO 24 HOUR AS SHOWERS WILL LOWER CIGS AND
VISIBILITIES AT ALL TAF SITES INCLUDING KRDM AND KDLS. WARM AIR
ALOFT MAY PROVIDE A PERIOD OF FREEZING RAIN AT KPDT...KALW...KDLS...
AND POSSIBLY KYKM. NEXT UPDATE WILL BE AT 12Z OR 4 AM LOCAL STANDARD
TIME.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 39 36 38 31 / 80 70 40 50
ALW 40 36 40 33 / 80 70 50 50
PSC 33 32 39 31 / 70 70 30 30
YKM 31 27 36 28 / 60 70 40 40
HRI 36 33 39 31 / 70 70 40 40
ELN 31 27 34 27 / 80 80 50 60
RDM 46 34 44 28 / 70 60 40 50
LGD 39 34 37 28 / 90 60 60 50
GCD 40 33 37 28 / 90 60 40 40
DLS 36 34 40 32 / 80 80 60 70
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR ORZ049-
050-502-503-506.
WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR ORZ044-504-505.
WINTER STORM WARNING UNTIL 10 AM PST THIS MORNING FOR ORZ041.
WINTER WEATHER ADVISORY UNTIL 6 AM PST EARLY THIS MORNING FOR
ORZ501.
WA...WINTER STORM WARNING UNTIL 6 PM PST THIS EVENING FOR WAZ026-027-
501.
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR WAZ502.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR WAZ030.
WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR WAZ028.
WINTER STORM WARNING UNTIL 10 AM PST THIS MORNING FOR WAZ024.
WINTER WEATHER ADVISORY UNTIL 6 AM PST EARLY THIS MORNING FOR
WAZ029.
&&
THREAT INDEX
TODAY : RED
WEDNESDAY : GREEN
THURSDAY : 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
$$
85/88/88
