FXUS66 KPDT 151810
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1010 AM PST TUE DEC 15 2009
.UPDATE...A VERY ACTIVE WEATHER DAY FOR THE REGION WITH A MIX OF
RAIN...FREEZING RAIN...SNOW...FREEZING FOG AND WIND DEPENDING ON
YOUR LOCATION. NUMEROUS WARNINGS AND ADVISORIES CONTINUE OVER THE
AREA. FREEZING RAIN CONTINUES TO BE A BIG ISSUE IN THE COLUMBIA
GORGE...BLUE MOUNTAIN FOOTHILLS AND COLUMBIA BASIN AS FAR NORTH AS
THE TRI-CITIES. EARLIER THINKING WAS THAT SOUTH WINDS WOULD PICK UP
AND START SCOURING OUT THE COLD AIR LATE THIS MORNING AND END THE
FREEZING RAIN. NOW THINKING IT WILL BE MORE LIKE MID AFTERNOON
ALTHOUGH SOME AREAS WILL WARM SOONER THAN OTHERS. FURTHER NORTH
AROUND HANFORD WILL LIKELY BE THE LAST TO REACH FREEZING...IF THEY
DO AT ALL. HAVE ALREADY EXTENDED WARNINGS AND ADVISORIES FOR THE
GORGE...BASIN AND FOOTHILLS ZONES UNTIL NOON AND ADDED A FREEZING
RAIN ADVISORY FOR NORTH CENTRAL OREGON. WILL DECIDE WHETHER TO
EXTEND THEM FURTHER IN THE NEXT HOUR OR TWO. WILL ALSO BE TAKING A
CLOSE LOOK AT TONIGHT. WITH TEMPERATURES BELOW FREEZING AND
SUBSTANTIAL PRECIPITATION EXPECTED...ADVISORIES AND WARNINGS MAY END
UP BEING EXTENDED THROUGH TONIGHT IN THE COLUMBIA BASIN AND THE
COLUMBIA GORGE. THE BLUE MOUNTAIN FOOTHILLS MAY REMAIN ABOVE
FREEZING OVERNIGHT SO THE THREAT FOR FREEZING RAIN IS LESS THERE. IN
CENTRAL OREGON AND UP TO MADRAS IN NORTH CENTRAL
OREGON...TEMPERATURES ARE ABOVE FREEZING AND EXPECTED TO REMAIN
THERE. THEY ARE RECEIVING RAIN AND THAT WILL CONTINUE THROUGH THE
DAY. ELSEWHERE...THE BLUE MOUNTAINS CONTINUE TO RECEIVE SNOW BUT
WALLOWA COUNTY AND MOUNTAINS IN THE SOUTH ARE LARGELY ABOVE FREEZING
SO MOST LOCATIONS THERE ARE RECEIVING RAIN. HAVE HAD A COUPLE OF
UPDATES ALREADY AND WILL UPDATE AGAIN SHORTLY TO TWEAK POPS AND
WEATHER AND ADJUST A COUPLE OF TEMPERATURES. PERRY
&&
.AVIATION...18Z TAFS...WARM AIR ALOFT IS MOVING OVER COOLER AIR AT
THE SURFACE ACROSS THE COLUMBIA BASIN OF OREGON AND
WASHINGTON...LEADING TO LIGHT FREEZING RAIN IMPACTING
KALW...KPDT...KDLS...KPSC AND KYKM THIS MORNING. EXPECT TEMPERATURES
AT THE SURFACE TO GRADUALLY INCREASE ABOVE FREEZING BY 20-22Z...WITH
PRECIPITATION CHANGING OVER TO RAIN. THE WEATHER SYSTEM WILL KEEP
PRECIPITATION CHANCES THROUGH THE DAY AND INTO THE EVENING. CEILINGS
AND VISIBILITIES WILL MAINLY BE IN THE MVFR CATEGORY TODAY WITH
CONDITIONS LOWERING TO IFR UNDER THE HEAVIER SHOWERS.
OVERNIGHT...PRECIPITATION WILL TAPER OFF WITH LOWER CEILINGS
REMAINING IN MIST. DMH
&&
.PREV DISCUSSION... /ISSUED 420 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
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 39 36 41 31 / 80 70 40 50
ALW 40 36 42 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 41 31 / 70 70 40 40
ELN 31 27 34 27 / 80 80 50 60
RDM 46 34 44 28 / 70 60 40 50
LGD 40 34 39 28 / 90 60 60 50
GCD 40 33 38 28 / 90 60 40 40
DLS 36 34 40 32 / 80 80 60 70
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR ORZ044-501.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR ORZ049-
050-503-506.
FREEZING RAIN ADVISORY UNTIL NOON PST TODAY FOR ORZ042.
WINTER STORM WARNING UNTIL 4 PM PST THIS AFTERNOON FOR ORZ502.
WINTER STORM WARNING UNTIL NOON PST TODAY FOR ORZ041.
WA...WINTER STORM WARNING UNTIL 6 PM PST THIS EVENING FOR WAZ026-027-
501.
WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR WAZ028-029-502.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR WAZ030.
WINTER STORM WARNING UNTIL NOON PST TODAY FOR WAZ024.
&&
THREAT INDEX
TODAY : RED
WEDNESDAY : YELLOW
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
$$
83/88/84
