FXUS66 KPDT 251121 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
321 AM PST WED NOV 25 2009
UPDATED AVIATION DISCUSSION
.SHORT TERM...TODAY THROUGH THURSDAY...HIGH PRESSURE ALOFT WILL
CONTINUE TO BUILD AND AMPLIFY OVER THE REGION TODAY AND TONIGHT.
THIS WILL KEEP ANY MOISTURE TO THE NORTH OF THE FORECAST AREA...
ESPECIALLY THIS MORNING. THE FLOW WILL BACK TO THE SOUTHWEST TONIGHT
AND ON THURSDAY AS THE NEXT WEATHER SYSTEM APPROACHES FROM THE WEST.
THIS WILL SLOWLY BRING INCREASING MOISTURE OVER THE CASCADE CREST OF
CENTRAL WA OVER ONTO THE EAST SLOPES. WILL HOLD ON TO ISOLATED
RAIN/SNOW THERE BEGINNING TONIGHT...BUT SLOWLY INCREASING IN AREAL
COVERAGE OVER TIME. THERE ARE AREAS OF LOW CLOUDS/FOG FORMING
ALREADY AS SEEN ON THE FOG LOOP SATELLITE IMAGERY...AND IT HAS ALSO
BEEN REPORTED BY SPOTTERS AS WELL...WITH LOWERING CEILINGS AND
VISIBILITY IN SURFACE OBSERVATIONS. CURRENTLY THE GREATEST FOG
POTENTIAL FOR THIS MORNING AND AGAIN TONIGHT WILL BE IN THE YAKIMA
AND KITTITAS VALLEY AS WELL AS THE LOWER COLUMBIA BASIN...ESPECIALLY
NEAR THE LARGER RIVERS SUCH AS THE COLUMBIA AND YAKIMA RIVERS. ONE
LAST CONCERN IS A TIGHT PRESSURE/TEMPERATURE GRADIENT BETWEEN THE
BAKER AND GRANDE RONDE VALLEY WHICH IS RESULTING IN WINDY
CONDITIONS...MAINLY NEAR LADD AND PYLES CANONS AND THE SOUTH END OF
THE GRANDE RONDE VALLEY. THE WINDS ARE LIKELY TO INCREASE THIS
MORNING TO ADVISORY LEVELS AND WILL LEAVE THE CURRENT WIND ADVISORY
GOING THROUGH THIS MORNING INTO EARLY AFTERNOON. TEMPERATURES WILL
BE MILD FOR THE TIME OF YEAR...ESPECIALLY IN FOG FREE AREAS AS WELL
AS IN THE HIGHER TERRAIN THAT IS ABOVE ANY STRONG TEMPERATURE
INVERSIONS.
.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...WITH A SLIGHTLY SLOWER
MOVEMENT TO THE FRONTAL SYSTEM THURSDAY I DELAYED THE ONSET OF
PRECIPITATION MOVING ACROSS THE FORECAST AREA THURSDAY NIGHT AND
EARLY FRIDAY. EXPECT THIS TO MAINLY BE A RAIN EVENT WITH SNOW LEVELS
DROPPING BEHIND THE FRONT LATE THURSDAY NIGHT AND ON FRIDAY. THE
TROUGH WILL BE OVER THE REGION FRIDAY PRODUCING SOME INSTABILITY
SHOWERS. THERE IS A FAST MOVING SYSTEM THAT DROPS INTO THE TROUGH
FRIDAY NIGHT AND EARLY SATURDAY THAT WILL RE-ENERGIZE THE SHOWER
ACTIVITY OVERNIGHT. THIS SYSTEM HAS THE POTENTIAL TO BRING SNOW DOWN
TO AROUND 1000 FEET WITH A MIX OF RAIN AND SNOW IN THE BASIN. THIS
SYSTEM EXITS ON SATURDAY AS A RIDGE OF HIGH PRESSURE BEGINS TO
REBUILD OVER THE REGION WITH THE RIDGE PERSISTING INTO LATE MONDAY
BEFORE A FAST MOVING SYSTEM PASSING TO THE NORTH CLIPS THE REGION
WITH A CHANCE OF SHOWERS. HIGH PRESSURE QUICKLY REBUILDS TUESDAY AND
WEDNESDAY.
&&
.AVIATION...12Z...VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS
WITH MAINLY HIGH CLOUDS ABOVE 15000 FT AGL. AN EXCEPTION WILL BE
SOME PATCHY MORNING FOG CREATING POSSIBLE MVFR VISIBILITIES ALONG
RIVERS IN THE COLUMBIA BASIN AFFECTING MAINLY KYKM...KDLS AND KPSC.
SURFACE WINDS WILL REMAIN UNDER 15 KTS AT ALL TAF LOCATIONS FOR THE
NEXT 24 HOURS.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 53 35 50 41 / 0 0 0 20
ALW 51 37 48 42 / 0 0 0 20
PSC 50 33 47 39 / 0 0 0 30
YKM 47 31 44 38 / 0 0 20 50
HRI 52 32 49 40 / 0 0 0 30
ELN 47 34 44 36 / 0 0 20 60
RDM 54 29 51 36 / 0 0 0 50
LGD 47 30 44 35 / 0 0 0 20
GCD 52 32 49 36 / 0 0 0 20
DLS 54 35 51 41 / 0 0 0 60
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR ORZ049.
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
$$
88/91/91
