Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 261723 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED AVIATION DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1025 AM PDT TUE MAY 26 2015

.SHORT TERM...TODAY AND TONIGHT...AN UPPER LEVEL CLOSED LOW PRESSURE
SYSTEM OVER EASTERN WASHINGTON THIS MORNING WILL MOVE VERY SLOWLY
SOUTHWARD AND BE OVER CENTRAL IDAHO BY EARLY WEDNESDAY MORNING. THIS
WILL PLACE MOST OF THE FORECAST CAST AREA UNDER AN UNSTABLE AIRMASS
RESULTING IN SHOWERS TODAY AND OVERNIGHT WITH POSSIBLE THUNDERSTORMS
DURING THE AFTERNOON AND EVENING PERIOD. CENTRAL OREGON WILL ESCAPE
THE SHOWERS AND SEE JUST SOME CLOUDS.

&&

.PREV DISCUSSION... /ISSUED 300 AM PDT TUE MAY 26 2015/

SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...AN UPPER LOW OVER
EASTERN WASHINGTON EARLY THIS MORNING WILL SLOWLY DRIFT SOUTHEAST
THROUGH THIS PERIOD. THIS LOW WILL BE CENTERED OVER EXTREME
NORTHEAST OREGON BY WEDNESDAY MORNING AND SOUTHERN IDAHO BY EARLY
THURSDAY MORNING. THUS A SEASONALLY MILD, BUT UNSTABLE AIR MASS WILL
PERSIST OVER THE INTERIOR NORTHWEST THROUGH MUCH OF THIS PERIOD. A
FEW SHOWERS WILL BE POSSIBLE THROUGH THIS MORNING OVER SOME OF OUR
NORTHERN ZONES. DAYTIME HEATING WILL CAUSE THE POTENTIAL FOR SHOWERS
TO INCREASE OVER THE REGION, WHILE ALSO ALLOWING FOR ISOLATED
THUNDERSTORMS. AT THIS TIME EXPECT ALL OF OUR WASHINGTON ZONES AND
OUR EASTERN ZONES IN OREGON TO SEE THE POTENTIAL FOR SHOWERS AND
STORMS THIS AFTERNOON AND EVENING. A FEW SHOWERS SHOULD PERSIST
OVERNIGHT INTO WEDNESDAY MORNING ACROSS MANY OF OUR NORTHERN AND
EASTERN ZONES. ISOLATED TO SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED AGAIN WEDNESDAY AFTERNOON AND EVENING.
SOME STABILIZATION IS EXPECTED FROM THE BASIN SOUTH INTO CENTRAL
OREGON. THUS WILL CONTINUE TO INDICATE SHOWERS AND STORMS ALONG AND
NEAR THE CASCADE CREST, AND FROM THE NORTHERN BLUE MOUNTAIN
FOOTHILLS SOUTH TO GRANT COUNTY AND EAST TO WALLOWA COUNTY. 90

LONG TERM...THURSDAY THROUGH MONDAY...THURSDAY A WEAK RIDGE BUILDS
OVER THE REGION, BUT HAVE KEPT A CHANCE OF A SHOWER IN THE HIGHER
TERRAIN IN THE EASTERN MOUNTAINS AND ALONG THE EAST SLOPES OF THE
CENTRAL WASHINGTON CASCADES FOR THURSDAY. THURSDAY NIGHT A WEAK FLAT
MID/UPPER LEVEL RIDGE IS OVER THE REGION WITH ASSOCIATED SINKING AIR
PROVIDING DRY CONDITIONS OVERNIGHT THROUGH FRIDAY MORNING. FRIDAY
THE RIDGE REMAINS OVER US WITH THE RIDGE AXIS HAVING MOVED EAST INTO
IDAHO, WHICH ALLOWS FLOW ALOFT TO BACK TO THE SOUTHWEST, WHICH
ENABLES PACIFIC MOISTURE TO BEGIN ENTERING THE REGION. THIS MOISTURE
FLUX INTO THE FORECAST AREA INCREASES THROUGH THE WEEKEND FOR A
CHANCE OF SHOWERS IN THE HIGHER TERRAIN OF CENTRAL AND NORTHEAST
OREGON ON SATURDAY AND SUNDAY AS WELL AS IN THE BLUE MOUNTAINS OF
SOUTHEAST WASHINGTON. DAYTIME SURFACE HEATING WILL YIELD MARGINALLY
INSTABILITY FOR A SLIGHT CHANCE OF AFTERNOON AND EARLY EVENING
THUNDERSTORMS OVER THE MOUNTAINS THROUGH MONDAY.  POLAN

AVIATION...18Z TAFS. UPPER LEVEL LOW OVER EASTERN WASHINGTON WILL
CONTINUE TO ROTATE WITH ISOLATED TO SCATTERED SHOWERS AND A FEW
THUNDERSTORMS THROUGH THE LATE AFTERNOON AND EVENING FOR AREA EXCEPT
KRDM AND KBDN. CEILINGS 080-100 OVERNIGHT WITH WINDS GENERALLY LESS
THAN 10 KTS. 93

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  75  52  78  53 /  20  20  30  10
ALW  76  56  78  57 /  30  30  30  20
PSC  80  58  84  53 /  20  30  20  10
YKM  77  55  82  54 /  40  40  20  10
HRI  79  54  83  52 /  20  20  20  10
ELN  77  54  82  54 /  40  40  20  20
RDM  74  41  77  43 /  10  10  10  10
LGD  71  50  73  48 /  40  40  40  30
GCD  75  48  76  47 /  10  10  20  20
DLS  78  57  83  58 /  10  10  10  10

&&

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

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

$$

91/93/93


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