Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 171751 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1051 AM PDT WED SEP 17 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH THURSDAY...RIDGE OF HIGH PRESSURE OVER
THE REGION IS BEGINNING TO SHIFT TO THE EAST AS A TROUGH OF LOW
PRESSURE OFF THE WEST COAST SLOWLY ADVANCES INLAND. ALREADY SEEING A
LOT OF CLOUDS SPREADING OF THE REGION TODAY BUT THE MAIN AREA OF
PRECIPITATION WILL REMAIN WEST OF THE CASCADES TODAY. SOME OF THIS
PRECIPITATION WILL SPREAD TO THE CASCADES BY LATE AFTERNOON AND
EARLY TONIGHT AT WHICH TIME THERE WILL BE SOME CHANCE OF
PRECIPITATION ALONG THE EAST SLOPES OF THE CASCADES THROUGH THE
NIGHT. ALSO EXPECTING SOME CONVECTION TO FIRE UP OVER SOUTHEAST
OREGON OVERNIGHT WITH SOME OF THIS POTENTIALLY CLIPPING THE ELKHORN
AND WALLOWA MOUNTAINS LATE OVERNIGHT THROUGH EARLY THURSDAY. THE
UPPER LEVEL TROUGH WILL BEGIN TO MOVE OVER THE REGION THURSDAY BUT
WEAKEN AND SPLIT WITH SOME ENERGY PASSING TO THE SOUTH AND THE OTHER
TO THE NORTH. THIS WILL WEAKEN THE SYSTEMS AND LIMIT THE CHANCE OF
PRECIPTATION TO LOW AMOUNTS IF ANY AT ALL. CLOUD COVER TODAY WILL
SUPPRESS TEMPERATURES A LITTLE TODAY AND THEN SLIGHTLY MORE COOLING
THURSDAY AS THE REMNANTS OF THE TROUGH PASSES.

.AVIATION...18Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS. MID TO HIGH LEVEL CLOUDS WILL STREAM OVER THE REGION AS A
SYSTEM OFF THE COAST MOVES ASHORE AND WEAKENS.  SOME SPRINKLES MAY
OCCUR AFTER 18/12Z...OTHERWISE CONTINUED DRY.  WINDS WILL GENERALLY
BE LESS THAN 10 KTS. EARLE

&&

.PREV DISC... /ISSUED 255 AM PDT WED SEP 17 2014/

SHORT TERM...TODAY THROUGH FRIDAY NIGHT...MID AND HIGH CLOUDS ARE
SPREADING OVER EASTERN WASHINGTON AND OREGON IN SOUTHERLY FLOW ALOFT
AHEAD OF A TROUGH LOCATED OFFSHORE. WATER VAPOR SATELLITE SHOWS A
WAVE MOVING THROUGH SOUTHEAST WASHINGTON AT THIS TIME. HOWEVER LOW
LEVELS ARE STILL VERY DRY SO VERY LITTLE...IF ANY...PRECIPITATION IS
REACHING THE GROUND. MORE WEAK WAVES WILL MOVE THROUGH THIS
AFTERNOON AND TONIGHT BUT THE MAIN EFFECT WILL BE TO INCREASE MID
LEVEL MOISTURE SO THAT A STRONGER WAVE ON THURSDAY WILL TRIGGER SOME
SHOWERS AND THUNDERSTORMS ACROSS EASTERN OREGON THURSDAY. A FEW
SHOWERS ARE POSSIBLE NEAR THE CASCADES TODAY. THERE IS SOME
INSTABILITY OVER THE CASCADES THAT MAY TRIGGER A FEW THUNDERSTORMS
ALONG THE OREGON CASCADES THIS AFTERNOON. STRONGER SOUTHERLY WINDS
ALOFT MAY MIX TO THE GROUND AT TIMES TODAY IN CENTRAL OREGON. WINDS
AND LOW RH MAY CAUSE FIRE WEATHER CONCERNS IN THE SOUTHERN HALF OF
FWZ 640 THIS AFTERNOON. THE TROUGH WILL MOVE ACROSS WASHINGTON AND
OREGON THURSDAY...BUT IT WILL BE SPLITTING APART AS IT MOVES
THROUGH. THERE WILL BE ENOUGH INSTABILITY WITH THE TROUGH THAT A FEW
THUNDERSTORMS WILL DEVELOP FROM CENTRAL TO NORTHEAST OREGON THURSDAY
AFTERNOON AND EVENING. FRIDAY THE UPPER LEVEL RIDGE WILL REBUILD
OVER WASHINGTON AND OREGON. THIS WILL DRY OUT EASTERN WASHINGTON AND
OREGON WITH A SUNNY WARM DAY...BUT A COOL NIGHT FRIDAY AS STRONG
RADIATIONAL COOLING WILL OCCUR UNDER CLEAR SKIES AND LIGHT WINDS.
COONFIELD

LONG TERM...SATURDAY THROUGH TUESDAY...A MID/UPPER LEVEL HIGH
PRESSURE RIDGE PERSISTS OVER THE PACIFIC NORTHWEST FROM THE WEEKEND
THROUGH MONDAY FOR DRY CONDITIONS AND DAYTIME HIGH TEMPERATURES 5-10
DEGREES ABOVE NORMAL. THE WIND FLOW ALOFT BACKS TO THE SOUTHWEST
MONDAY NIGHT AND TUESDAY AS A RESULT OF THE RIDGE AXIS MOVING EAST
OF THE FORECAST AREA, THUS ALLOWING FOR INCREASING MID AND HIGH
CLOUDS SPREADING OVER THE REGION MONDAY NIGHT AND TUESDAY. THE
CLOUDS WILL MODERATE THE DAYTIME HIGH TEMPERATURES ON TUESDAY. POLAN

AVIATION...12Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS. THERE WILL BE MID AND HIGH CLOUDS BETWEEN MAINLY 150-250 FT
TONIGHT AND WEDNESDAY. AT THIS TIME IT LOOKS LIKE ANY THUNDERSTORMS
WILL STAY TO THE WEST OF KRDM AND KBDN ON WEDNESDAY AFTERNOON. WINDS
WILL REMAIN GENERALLY LIGHT AND 15 KTS OR LESS THROUGH THE PERIOD.
POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  85  58  81  54 /   0  10  20  20
ALW  86  63  81  60 /   0  10  20  20
PSC  85  57  84  58 /   0  10  10  10
YKM  82  57  79  54 /  10  20  10  10
HRI  85  57  83  55 /   0  10  10  10
ELN  82  55  78  54 /  10  20  20  20
RDM  85  51  75  44 /  10  20  20  20
LGD  89  54  80  50 /   0  10  20  20
GCD  86  50  78  48 /   0  10  20  20
DLS  81  62  80  57 /  10  20  20  20

&&

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

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

$$

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