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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
300 AM PDT TUE APR 21 2015

.SHORT TERM...TODAY THROUGH THURSDAY...THE FORECAST AREA CAN EXPECT 
ONE MORE DAY OF WARM TEMPERATURES AND DRY CONDITIONS AS AN UPPER 
RIDGE CONTINUES TO INFLUENCE THE CWA. EXPECT HIGH TEMPERATURES TO BE 
SIMILAR TO MONDAY WITH READINGS IN THE 70S TO LOWER 80S IN THE LOWER 
ELEVATIONS AND MAINLY 60S IN THE MOUNTAINS. A COLD FRONT AND UPPER 
TROUGH WILL MOVE INTO THE REGION TONIGHT AND WEDNESDAY. THIS WILL 
BRING SIGNIFICANTLY COOLER TEMPERATURES...RAIN SHOWERS AND POSSIBLE 
THUNDERSTORMS AS WELL AS INCREASING WINDS DUE TO A TIGHTENING 
PRESSURE GRADIENT. MAIN THREAT FOR THUNDERSTORMS WILL BE OVER 
CENTRAL OREGON LATE THIS AFTERNOON AND THIS EVENING. THE WINDS WILL 
INCREASE ENOUGH IN THE KITTITAS VALLEY TO WARRANT A WIND ADVISORY 
THERE BEGINNING AT MIDNIGHT TONIGHT AND CONTINUING THROUGH 8 PM 
WEDNESDAY. ELSEWHERE IT WILL BECOME BREEZY TO WINDY AS WELL BUT 
WINDS NOT AS STRONG AS IN THE KITTITAS VALLEY. TEMPERATURES WILL 
COOL DOWN TO THE 60S IN THE LOWER ELEVATIONS AND MID 40S TO MID 50S 
MOUNTAINS FOR WEDNESDAY AND THURSDAY. A PROGRESSIVE PATTERN WILL 
PERSIST INTO THURSDAY WITH ANOTHER TROUGH AND COLD FRONT MOVING INTO 
THE CWA...KEEPING TEMPERATURES COOL AND POSSIBLE MAINLY MOUNTAIN 
SHOWERS. WINDS WILL BE LIGHTER ON THURSDAY BUT IT IS STILL EXPECTED 
TO BECOME BREEZY IN THE AFTERNOON IN THE KITTITAS VALLEY AND THE 
EASTERN COLUMBIA RIVER GORGE. 88

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY...THE EXTENDED PERIOD 
CONTINUES THE PROGRESSIVE UPPER LEVEL FLOW PATTERN, THUS ALLOWING 
PACIFIC SYSTEMS TO MOVE INTO THE REGION. THURSDAY NIGHT THE 00Z GFS 
AND ECMWF RUNS INDICATE THE UPPER LEVEL TROUGH MOVING SOUTHEAST OVER 
SOUTHERN BRITISH COLUMBIA AND THE PACIFIC NORTHWEST. THE MAIN 
DYNAMIC LIFT WILL REMAIN WEST OF THE CASCADES THROUGH OVERNIGHT AND 
THEN ON FRIDAY THE UPPER TROUGH PERSISTS OVER VANCOUVER ISLAND THUS 
KEEPING FORECAST AREA N A SOUTHWEST FLOW ALOFT, WHICH KEEPING 
MOISTURE STREAMING ACROSS THE EASTERN PORTIONS OF WASHINGTON AND 
OREGON FOR A CHANCE OF SHOWERS IN THE BLUE MOUNTAINS. DOWNSLOPE 
WESTERLIES ALOFT WILL KEEP CENTRAL AND NORTH CENTRAL OREGON MAINLY 
DRY DURING FRIDAY. SNOW LEVELS ON FRIDAY WILL BE 4000-5000 FEET. 
FRIDAY NIGHT A BASIC WESTERLY FLOW ALOFT WILL KEEP DOWNSLOPE SINKING 
AIR WHICH WILL BRING DRY CONDITIONS TO THE REGION. OVER THE WEEKEND 
A VERY LARGE LONGWAVE TROUGH SLOWLY MOVES TOWARD THE COAST AND 
PUSHES A WARM FRONT AS WELL TOWARD THE COAST, BUT THE FRONT STAYS 
OFFSHORE THROUGH SUNDAY FOR DRY CONDITIONS. SUNDAY NIGHT AND MONDAY 
THE FRONT PUSHES INLAND FOR INCREASING POPS.  POLAN

&&

.AVIATION...06Z TAFS. MAINLY CLEAR SKIES TONIGHT. INCREASING CIRRUS 
TUESDAY. SCT CUMULUS OVER THE MOUNTAINS IN THE AFTERNOON AND 
EVENING. SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS RDM BDN AFTER 
00Z. LIGHT WINDS TONIGHT THEN WESTERLY WINDS INCREASING TUESDAY TO 
10-25KT.   POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  76  47  60  34 /  10  10  10   0 
ALW  76  49  61  38 /  10  10  10   0 
PSC  81  48  67  38 /   0  10  10   0 
YKM  79  47  64  37 /  10  10  10   0 
HRI  81  47  66  36 /   0  10  10   0 
ELN  77  46  60  38 /  10  10  10   0 
RDM  73  35  60  25 /  20  20  10   0 
LGD  76  45  59  32 /  10  20  30  10 
GCD  76  40  61  32 /  10  30  40  10 
DLS  75  49  61  39 /  10  10  10   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...WIND ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM PDT WEDNESDAY 
WAZ026.

&&

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

$$

88/99/99









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