Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 251754 AAA
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1050 AM PDT SAT OCT 25 2014

UPDATED AVIATION

.SHORT TERM...MORNING UPDATE...A DEEP UPPER LEVEL LOW, CURRENTLY OFF
THE OREGON COAST, WILL MOVE INTO WESTERN WASHINGTON BY LATE THIS
AFTERNOON. THIS LOW WILL THEN MOVE INTO SOUTHERN BRITISH COLUMBIA BY
MIDNIGHT, AND WORK INTO ALBERTA BY DAYBREAK SUNDAY. THE MAIN IMPACT
OF THIS SYSTEM WILL BE WIND. LOCALLY TIGHT PRESSURE GRADIENTS OVER
CENTRAL OREGON AND THE SOUTHERN GRANDE RONDE VALLEY WILL ALLOW
STRONGER WINDS ALOFT TO MIX DOWN TODAY INTO EARLY EVENING. THUS WILL
CONTINUE THE CURRENT WIND ADVISORIES IN THESE TWO LOCATIONS. STRONG
WIND GUSTS WILL BE POSSIBLE OVER RIDGES ABOVE 5500 FEET THROUGH
TODAY AS WELL. LOCAL WIND GUSTS OF 30 TO 40 MPH WILL ALSO BE
POSSIBLE IN SOUTH-NORTH ALIGNED PORTIONS OF THE JOHN DAY BASIN. FOG
ALONG THE BLUE MOUNTAIN FOOTHILLS WILL GRADUALLY BURN OFF THIS
MORNING, WITH BREEZY SOUTHEAST TO SOUTHWEST WINDS POSSIBLE LATER
TODAY. THESE WINDS SHOULD CAUSE A DRAMATIC WARM UP ALONG THE
FOOTHILLS. THE SYSTEM`S COLD FRONT WILL SWING ACROSS THE REGION THIS
EVENING. IT`S PASSAGE WILL HELP TO END THE STRONGER WINDS IN CENTRAL
OREGON AND IN THE GRANDE RONDE VALLEY. AT THE SAME TIME, WINDS WILL
INCREASE ACROSS THE COLUMBIA BASIN. INITIALLY SOME LOCATIONS WILL
SEE STRONG WINDS WITH THE FRONTAL PASSAGE, OTHERWISE WINDS WILL
GRADUALLY BECOME PERSISTENT IN THE 25 TO 35 MPH RANGE OVERNIGHT DUE
TO TIGHTENING PRESSURE GRADIENTS. THUS WILL CONTINUE THE CURRENT
WIND ADVISORIES FOR THE FOOTHILLS AND THE LOWER BASIN. WILL MOST
LIKELY ADD ADVISORIES FOR NORTH-CENTRAL OREGON AND THE SIMCOE
HIGHLANDS FOR THIS EVENING INTO SUNDAY. SOME SHOWERS WILL ACCOMPANY
THIS SYSTEM. SNOW LEVELS WILL FALL OVERNIGHT, THUS LIGHT SNOW
ACCUMULATIONS FROM SNOW SHOWERS WILL BE POSSIBLE SUNDAY IN THE
MOUNTAINS. 90

.LONG TERM...PREVIOUS DISCUSSION...IT WILL BE WET WITH NEAR TO ABOVE
SEASONAL TEMPERATURES DURING THE EXTENDED PERIOD. A PROGRESSIVE FLOW
PATTERN WILL KEEP PERIODS OF RAIN THROUGH THE END OF THE WEEK.
ECMWF AND GFS ARE IN FAIR AGREEMENT, ALTHOUGH THERE ARE SOME TIMING
DIFFERENCES WITH A DEEPENING TROUGH OFFSHORE ON FRIDAY. THE GFS IS
ABOUT 6 HOURS FASTER PUSHING THE TROUGH INLAND COMPARED TO THE
ECMWF, BUT THE DIFFERENCES DO NOT HAVE A SIGNIFICANT IMPACT ON THE
FORECAST. SNOW LEVELS WILL REMAIN HIGH THROUGH MOST OF THE EXTENDED,
AND ONLY THE HIGHER PEAKS OF THE CASCADES, WALLOWAS, AND THE
STRAWBERRY WILDERNESS WILL SEE SNOW.

&&

.AVIATION...18Z TAFS...IFR/LIFR TO CONTINUE AT KALW AND KPDT UNTIL
LOW LEVEL GRADIENT INCREASES AND SOUTH WINDS KICK IN 21Z-23Z...THEN
QUICKLY BECOMING VFR AS ARE OTHER TAF SITES CURRENTLY. ALTHOUGH 17Z
KPSC METAR SHOWS VFR CONDITIONS...KEPT TEMPO FOR IFR TIL 19Z AS
WEBCAMS IN AREA SHOW LOWER VSBY AND CLOUDS HANGING AROUND. NEXT
CHALLENGE IS WIND WITH STRONG UPPER LEVEL TROF AND TIGHTENING
SURFACE GRADIENT.  WIND G25-35KT WILL OCCUR AT ALL TAF SITES
ESPECIALLY 00Z-12Z. T.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  68  45  60  40 /  20  30  20  20
ALW  67  48  59  43 /  20  40  30  20
PSC  63  48  65  40 /  20  30  20  10
YKM  56  42  59  36 /  30  50  20  10
HRI  65  46  64  38 /  20  30  20  10
ELN  56  41  58  35 /  40  50  20  10
RDM  63  37  56  28 /  20  40  20  20
LGD  66  44  55  36 /  20  40  40  30
GCD  64  42  55  34 /  20  40  30  20
DLS  60  46  60  42 /  50  60  30  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY FROM 5 PM THIS AFTERNOON TO 3 PM PDT SUNDAY
     ORZ044-507-508.

     WIND ADVISORY UNTIL 11 PM PDT THIS EVENING ORZ511.

     WIND ADVISORY UNTIL 8 PM PDT THIS EVENING FOR LADD AND PYLES
     CANYONS IN THE ORZ049.

WA...WIND ADVISORY FROM 5 PM THIS AFTERNOON TO 3 PM PDT SUNDAY
     WAZ028-029.

&&

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

$$

90/85/79






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