AREA FORECAST DISCUSSION
FXUS66 KPDT 241025
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
225 AM AM PST TUE NOV 24 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...A WEAK PACIFIC WEATHER
DISTURBANCE IS CURRENTLY CROSSING THE REGION WITH AN EMBEDDED WEAK
UPPER TROUGH IN THE FLOW. THIS SYSTEM IS PRODUCING SOME LIGHT
PRECIP...MAINLY OVER THE CASCADE CREST AND EAST SLOPES. THE AIR OVER
THE CREST IS ABOVE FREEZING GENERALLY IN THE MID TO UPPER 30S. THERE
MAY BE A FEW ISOLATED POCKETS OF BELOW FREEZING AIR IN THE CANYONS
AND VALLEYS SO CANNOT COMPLETELY RULE OUT VERY LIGHT AND LOCAL
FREEZING RAIN OR DRIZZLE THIS MORNING. TEMPERATURES WILL RISE ABOVE
FREEZING AFTER DAY BREAK AND CHANGE ANY PRECIPITATION TO JUST RAIN.
HIGH PRESSURE ALOFT WILL STRENGTHEN AND AMPLIFY TONIGHT THROUGH AT
LEAST WEDNESDAY NIGHT KEEPING MOISTURE AND ENERGY WITH ANY PACIFIC
STORMS TO THE NORTH OF THE CWA. AS SUCH WILL HAVE A MOSTLY DRY
FORECAST FOR THE CWA...EXCEPT THE CENTRAL WASHINGTON CASCADE
CREST/EAST SLOPES WHICH MAY STILL RECEIVE SOME SLOP OVER LIGHT
PRECIP FROM THE WEST. VALLEY AND COLUMBIA BASIN INVERSIONS WILL
DEVELOP OVER AREAS OF NORTHERN AND NORTHEAST OREGON AND THE COLUMBIA
BASIN AND ADJACENT VALLEYS IN WASHINGTON. THIS COULD BE THE FIRST
REAL FOG EPISODE OF THE SEASON DUE THE RECENT MOISTURE THAT FELL
OVER THE REGION AND THAT WHICH FALLS TODAY. ANY FOG THAT FORMS WILL
FIRST FORM ALONG THE LARGER RIVERS AND STREAMS AND THEN WILL EXPAND
TO COVER A GREATER AREA OF THE COLUMBIA BASIN AND ADJACENT VALLEYS.
THIS WILL KEEP TEMPERATURES DOWN DURING THE DAY AND UP AT NIGHT
WHILE IN THE HIGHER TERRAIN MILD TEMPERATURES CAN BE EXPECTED DURING
THE DAY WITH COLD FROSTY NIGHTS. 88
.LONG TERM...THURSDAY THROUGH MONDAY...MAIN WEATHER CONCERN DURING
THIS PERIOD WILL OCCUR THURSDAY NIGHT AND FRIDAY. A COLD FRONT WILL
SLOWLY MAKE ITS WAY ACROSS THE FORECAST AREA LATE THURSDAY. MOST OF
THE FORECAST AREA WILL ENJOY A DRY THANKSGIVING DAY WITH THE
EXCEPTION OF THE CASCADES WHERE SOME RAIN WILL BEGIN DURING THE DAY
AS THE FRONT APPROACHES THE CASCADES. THE FRONT WILL MOVE THROUGH
THE FORECAST AREA THURSDAY NIGHT WITH LOWERING SNOW LEVELS. THE
TROUGH WITH ITS ASSOCIATED COLD AIR WILL PASS OVER THE REGION FRIDAY
RESULTING IN SHOWERS MAINLY OVER THE MOUNTAINS. HIGH PRESSURE WILL
THEN REBUILD OVER THE REGION SATURDAY AND SUNDAY WITH THE MAIN STORM
TRACK NORTH OF THE FORECAST AREA. THE WASHINGTON CASCADES WOULD BE
ABOUT THE ONLY AREA THREATENED WITH A CHANCE OF PRECIPITATION.
ANOTHER WEATHER SYSTEM LOOKS LIKE IT WILL CLIP THE REGION ON MONDAY
BUT NOT BE MUCH OF A PRECIPITATION PRODUCER.
&&
.AVIATION...12Z TAFS...VFR CONDITIONS WILL BE PREVALENT FOR THE NEXT
24 HOURS. A WEATHER DISTURBANCE WILL MOVE THROUGH THE AREA TODAY
WITH BROKEN-OVERCAST SKIES SKIES GENERALLY ABOVE 5000 FEET AGL.
SCATTERED RAIN SHOWERS WILL ACCOMPANY THE SYSTEM AND COULD LOWER
CEILINGS AND VISIBILITIES TO MVFR LEVELS NEAR THE HEAVIER SHOWERS
MAINLY ACROSS SOUTHERN WASHINGTON TODAY. SHOWERS WILL END AND SKIES
WILL PARTIALLY THIS AFTERNOON AND EVENING. SURFACE WINDS WILL
PRIMARILY STAY BELOW 15 KTS FOR THE NEXT 24 HOURS BUT COULD REACH 10
TO 20 KTS BRIEFLY NEAR THE HEAVIER SHOWERS.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 48 34 44 34 / 20 0 0 0
ALW 47 36 41 31 / 20 0 0 0
PSC 50 33 46 32 / 20 0 0 0
YKM 48 31 45 32 / 20 0 0 0
HRI 48 32 45 30 / 20 0 0 0
ELN 47 32 44 30 / 20 10 10 10
RDM 52 26 50 28 / 10 0 0 0
LGD 44 28 43 31 / 20 10 10 10
GCD 47 28 52 25 / 10 0 0 0
DLS 51 38 52 36 / 20 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&
THREAT INDEX
TODAY : GREEN
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
88/91/91