Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 291130 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
430 AM PDT FRI AUG 29 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH SUNDAY...A WESTERLY FLOW ALOFT WILL
CONTINUE TO BRING IN COOLER MARINE AIR INTO THE FORECAST AREA
TODAY...ESPECIALLY WESTERN AREAS OF THE CWA. A MOSTLY DRY COLD FRONT
WILL SWEEP ACROSS THE FORECAST AREA THIS AFTERNOON AND TONIGHT.
SURFACE PRESSURE GRADIENTS WILL INCREASE AHEAD OF THIS COLD FRONT
CAUSING SOUTHWEST TO WEST WINDS TO INCREASE...ESPECIALLY IN THE
EASTERN COLUMBIA RIVER GORGE AND IN THE KITTITAS VALLEY ALONG THE
CASCADE EAST SLOPES. THIS COMBINED WITH MODERATELY LOW RELATIVE
HUMIDITIES WILL LEAD TO HEIGHTENED FIRE WEATHER CONCERNS. HOWEVER
RELATIVE HUMIDITIES WILL BE HIGH ENOUGH TO PREVENT RED FLAG
CONDITIONS FROM BEING MET. THEREFORE WILL RECOMMEND TO FIRE WEATHER
SHIFT TO ONLY INCLUDE A HEADLINE IN THE FIRE WEATHER FORECAST TODAY.
OTHERWISE IT WILL BECOME COOLER TODAY THAN ON THURSDAY AND THEN EVEN
COOLER ON SATURDAY AND SUNDAY. THE ATMOSPHERE WILL BE STABLE FOR THE
MOST PART. THE ONLY CHANCE FOR PRECIPITATION TODAY WILL BE ALONG THE
CASCADE EAST SLOPES WHERE SOME MOISTURE WILL SPILL OVER THE CASCADE
CREST ONTO THE EAST SLOPES. DOWN SLOPE WINDS ON THE LEE OF THE
CASCADES WILL CAUSE QUICK DRYING OF THIS AIR SO AM NOT EXPECTING
PRECIPITATION TO MAKE IT TOO FAR EASTWARD AND MAINLY JUST OVER THE
HIGHER ELEVATIONS OF THE EAST SLOPES. ON THE OTHER SIDE OF THE CWA
THE NORTHEAST OREGON/SOUTHEAST WASHINGTON MOUNTAINS WILL CREATE
UPSLOPE WIND CONDITIONS AND THERE MAY BE A FEW SHOWERS THERE AS WELL
BEGINNING THIS EVENING. IT WILL BE TOO STABLE FOR THUNDERSTORMS. IT
WILL BE MORE UNSTABLE SOUTH AND EAST OF THE CWA WHERE THUNDERSTORMS
WILL BE POSSIBLE SOUTH AND EAST OF THE CWA BORDER. A BROAD UPPER
TROUGH WILL SAG SOUTHWARD INTO THE REGION TONIGHT AND SATURDAY
RESULTING IN FURTHER COOLING AND A CONTINUED SLIGHT CHANCE OF
SHOWERS OVER THE CASCADE EAST SLOPES. THE WINDS WILL NO LONGER FAVOR
UPSLOPE CONDITIONS OVER THE NORTHEAST MOUNTAINS BEGINNING SATURDAY
AS THEY BECOME MORE SOUTHWEST SO THE EASTERN AND NORTHEAST MOUNTAINS
WILL LIKELY NOT SEE ANYMORE SHOWERS STARTING SATURDAY. THIS GENERAL
PATTERN WILL PERSIST ON SUNDAY INTO THE EXTENDED FORECAST PERIOD. IT
WILL BECOME BREEZY TO WINDY AGAIN ON SATURDAY AND SUNDAY IN THE
EASTERN COLUMBIA RIVER GORGE AND KITTITAS VALLEY. TEMPERATURES WILL
COOL TO THE 70S IN THE LOWER ELEVATIONS BY SATURDAY AND CONTINUE ON
SUNDAY. 88

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...NORTHWEST FLOW WILL BE
OVER EASTERN WASHINGTON AND OREGON SUNDAY NIGHT THROUGH MONDAY
NIGHT. THE MAIN LIFT WILL REMAIN IN CANADA...BUT WEAK WAVES IN THE
FLOW MAY TRIGGER A FEW SHOWERS IN THE WASHINGTON CASCADES SUNDAY
NIGHT AND MONDAY. TUESDAY A TROUGH WILL DROP SOUTH OUT OF THE GULF
OF ALASKA CHANGING THE UPPER LEVEL FLOW TO WEST TUESDAY THEN
SOUTHWEST WEDNESDAY AND THURSDAY. MODELS SHOW SOME DIFFERENCES IN
TIMING/STRENGTH OF THE TROUGH BUT THE SIGNIFICANT MOISTURE AND LIFT
REMAINS NORTH OF THE CWA. DID NOT CHANGE CURRENT FORECAST OF SLIGHT
CHANCE POPS IN THE MOUNTAINS BUT WOULD NOT BE SURPRISED TO SEE
CHANGES IN PRECIPITATION FORECAST.  COONFIELD

&&

.AVIATION...12Z TAFS...VFR CONDITIONS WILL BE PREVALENT FOR THE NEXT
24 HOURS WITH INCREASING CIRRUS. WINDS WILL REMAIN BELOW 10 KTS THIS
MORNING...THEN INCREASE AGAIN AFTER 18Z WITH WINDS 10 TO 20 KTS AND
GUSTS TO 30 KTS.  76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  82  54  73  51 /   0  10  10  10
ALW  84  58  75  54 /   0  10  10  10
PSC  86  57  79  53 /   0  10  10  10
YKM  79  53  74  51 /   0  10  10  10
HRI  85  56  77  53 /   0  10  10  10
ELN  75  52  69  50 /   0  10  10  10
RDM  80  48  70  42 /   0  10  10  10
LGD  82  52  69  45 /  10  20  10  10
GCD  83  49  70  43 /  10  10  10  10
DLS  78  56  74  55 /   0  10  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.

&&

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

88/76/76





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