FXUS66 KPDT 091650
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
850 AM PST WED DEC 9 2009
.UPDATE...THE REGION CONTINUES TO BE UNDER A COLD AND DRY NORTHERLY
FLOW THIS MORNING. A WEAK DISTURBANCE EAST OF THE REGION BROUGHT MID
TO HIGH LEVEL CLOUDS ACROSS SOUTHEAST WASHINGTON AND PORTIONS OF
NORTHEAST OREGON OVERNIGHT AND THIS MORNING. THIS CLOUD COVER HAS
LED TO SEVERAL LOCATIONS BEING ANYWHERE FROM A FEW DEGREES WARMER TO
15 DEGREES WARMER THIS MORNING THAN YESTERDAY MORNING AT THIS TIME.
THESE CLOUDS WILL GRADUALLY DISSIPATE LATER THIS AFTERNOON.
TEMPERATURES THIS AFTERNOON WILL BE SIMILAR TO YESTERDAY AS COLDER
AIR REMAINS OVER THE AREA IN THE NORTHERLY FLOW. SOME LOCATIONS THAT
SEE MORE SUNLIGHT TODAY AND ARE ABOVE THE INVERSION MAY SEE A FEW
DEGREES WARMER THAN YESTERDAY AFTERNOON. CURRENT FORECAST LOOKS TO
BE ON TRACK AND DO NOT ANTICIPATE UPDATES THIS MORNING. DMH
&&
.AVIATION...18Z TAFS...VFR CONDITIONS WITH JUST A FEW HIGH CLOUDS
EXPECTED. WINDS WILL BE LIGHT AND VARIABLE.
&&
.PREV DISCUSSION... /ISSUED 355 AM PST WED DEC 9 2009/
SHORT TERM...TODAY THROUGH FRIDAY...A COLD AND DRY NORTHERLY FLOW
WILL BE OVER EASTERN WASHINGTON AND OREGON TODAY. WITH CLEAR
SKIES AND LIGHT WINDS TEMPERATURES HAVE PLUMMETED AGAIN. EXPECT
TEMPERATURES SIMILAR TO YESTERDAY. A WAVE MOVING INTO MONTANA WILL
BRING A FEW MORE HIGH CLOUDS TO THE COLUMBIA BASIN AND NORTHEAST
OREGON THIS MORNING...BUT THESE WILL PASS QUICKLY AND CLEAR UP IN
THE AFTERNOON AND EARLY EVENING. BY TONIGHT THE UPPER LEVEL FLOW
WILL BECOME MORE NORTHWEST WITH INCREASING 1000-500 MB THICKNESS.
850 MB WINDS BECOME SOUTHWEST. EXPECT COLD AIR TO REMAIN TRAPPED
UNDER STRONG SURFACE INVERSIONS IN THE COLUMBIA BASIN BUT OTHER
AREAS SHOULD SHOW MODERATING TEMPERATURES. HOWEVER...MOSTLY CLEAR
CLEAR SKIES AND LIGHT WINDS STILL PROMOTE STRONG RADIATIONAL COOLING
FOR ANOTHER VERY COLD NIGHT. THURSDAY AND FRIDAY NORTHWEST FLOW
ALOFT WITH WARMING TEMPERATURES AT 850 MB WILL CONTINUE.
TEMPERATURES WILL SLOWLY INCREASE...PARTICULARLY AT HIGHER
ELEVATIONS IN OREGON WHERE SOME MIXING WILL GET THE WARMER AIR ALOFT
TO THE SURFACE. COONFIELD
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...THE UNSEASONABLY COLD
AIR MASS WILL PERSIST THROUGH MONDAY WITH DAYTIME TEMPERATURES
STRUGGLING TO WARM ABOVE 30 DEGREES EACH DAY. ON FRIDAY NIGHT
THROUGH SATURDAY NIGHT THE FORECAST AREA WILL BE IN BETWEEN THE
NORTHERN JET STREAM OVER BRITISH COLUMBIA AND THE SOUTHERN JET
STREAM OVER CALIFORNIA. THE NORTHERN JET STREAM WILL DIG SOUTH
FRIDAY NIGHT AND SATURDAY THUS ALLOWING A MID/UPPER LEVEL TROUGH TO
SWING INTO THE FORECAST AREA ON SATURDAY/SATURDAY NIGHT...THUS
BRINGING A CHANCE OF SNOW INTO THE FORECAST AREA AND SNOW LIKELY IN
THE BLUE MOUNTAINS. HOWEVER...THE TROUGH WILL TRANSPORT A LAYER OF
WARMER AIR ALOFT...2-3 DEGREES ABOVE FREEZING...AROUND 4000-5000
FEET ABOVE MSL INTO CENTRAL AND NORTH CENTRAL OREGON SATURDAY AND
SATURDAY NIGHT RESULTING IN A WINTERY MIX OF SNOW...SLEET AND
FREEZING RAIN AT LOWER ELEVATIONS. ON SUNDAY A NORTHWEST FLOW ALOFT
AND ASSOCIATED OROGRAPHIC LIFT WILL COMBINE WITH DYNAMIC LIFT
ASSOCIATED WITH THE MID/UPPER LEVEL TROUGH AS THE TROUGH MOVES
THROUGH SOUTHEAST WASHINGTON AND NORTHEAST OREGON FOR SNOW LIKELY IN
THE BLUE MOUNTAINS. AN UPPER LEVEL RIDGE OF HIGH PRESSURE THEN
BUILDS OVER THE REGION FOR DRIER CONDITIONS MONDAY. A WARM FRONT
MOVES INTO THE REGION MONDAY NIGHT AND TUESDAY CAUSING SNOW MONDAY
NIGHT AND TUESDAY WITH SNOW CHANGING TO RAIN AT LOWER ELEVATIONS
DURING THE DAY ON TUESDAY. POLAN
AVIATION...12Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS. CURRENTLY CLEAR TO MOSTLY CLEAR SKIES IN CENTRAL OREGON AND
AT KRDM AND KBDN WILL LIKELY CONTINUE FOR THE REST OF TONIGHT. KRDM
AND KBDN WILL THEN HAVE CLEAR SKIES AFTER 15Z THROUGH THE REMAINDER
OF THE 24 HOUR PERIOD. KDLS AND KYKM WILL SEE SCATTERED TO BROKEN
CIRRUS AND SCATTERED MID LEVEL CLOUDS ABOVE 12000 FT AGL UNTIL
AROUND 16Z AND BECOMING CLEAR THEREAFTER. KPSC...KALW... KPDT...THE
BLUE MOUNTAINS AND NORTHEAST OREGON WILL SEE SOME BROKEN MID LEVEL
CLOUDS AROUND 13000-15000 FT MSL MOVE IN FROM THE NORTH BEFORE
DAYBREAK WITH CLOUD BASES LOWERING TO 8000-9000 FT AGL THIS MORNING
FOLLOWED BY CLEARING SKIES THIS AFTERNOON. ALL OF TONIGHT WILL HAVE
CLEAR SKIES. WINDS WILL REMAIN UNDER 10 KTS AT ALL LOCATIONS. POLAN
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 17 5 20 12 / 0 0 0 0
ALW 20 10 21 15 / 0 0 0 0
PSC 22 6 22 11 / 0 0 0 0
YKM 21 1 21 8 / 0 0 0 0
HRI 19 4 22 11 / 0 0 0 0
ELN 19 1 21 7 / 0 0 0 0
RDM 14 -6 23 6 / 0 0 0 0
LGD 14 1 20 10 / 0 0 0 0
GCD 15 0 22 11 / 0 0 0 0
DLS 18 7 22 15 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&
THREAT INDEX
TODAY : GREEN
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
$$
84/78/78
