Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 201759 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1059 AM PDT WED AUG 20 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY AND TONIGHT...FORECAST AREA WILL CONTINUE TO BE
UNDER A WEAK CYCLONIC FLOW OUT OF THE NORTHWEST. THERE WILL CONTINUE
TO BE A LITTLE INSTABILITY NEAR THE IDAHO BORDER FOR THE THREAT OF
SHOWERS AND OR THUNDERSTORMS FOR LATE AFTERNOON THROUGH EVENING.
OTHERWISE THE FORECAST AREA WILL REMAIN DRY...COOLER AND BREEZY.

&&

.AVIATION...18Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS. BKN-OVC CIRRUS AT 20K FT AGL AT KYKM, KDLS, KPSC, KPDT AND
KALW. KRDM WILL HAVE SCT STRATOCUMULUS AT 4K FT AGL INTO EARLY
AFTERNOON. KBDN WILL HAVE BKN STRATOCUMULUS UNTIL AROUND 22Z, THEN
SCT 5K FT AGL FOR REMAINDER OF THIS AFTERNOON. SKIES THEN BECOMING
MAINLY CLEAR BY 00Z-03Z/21ST. SUSTAINED WINDS INCREASING TO 10-20
KTS IN THE AFTERNOON. KDLS WILL HAVE GUSTS OF 25-30 KTS THIS
AFTERNOON.  POLAN

&&

.PREVIOUS DISCUSSIONS... /ISSUED 225 AM PDT WED AUG 20 2014/

SHORT TERM...TODAY THROUGH FRIDAY...AN UPPER TROUGH OVER THE REGION
WILL PERSIST THROUGH THE EXTENDED FORECAST PERIOD. THE TROUGH AXIS
WILL MOVE EASTWARD SLIGHTLY CAUSING A NORTHWEST FLOW ON THE BACK
SIDE OF THE TROUGH FOR TODAY THROUGH THURSDAY MORNING OVER THE CWA.
THIS WILL KEEP DRY AND STABLE CONDITIONS OVER THE CWA THROUGH THAT
TIME PERIOD. MAX TEMPERATURES WILL BE ON A COOLING TREND WITH HIGHS
ONLY IN THE MID 70S TO LOWER 80S...EXCEPT 60S TO LOWER 70S
MOUNTAINS. OVERNIGHT LOWS WILL RANGE FROM THE MID 30S TO MID 40S
MOUNTAINS TO THE 50S IN THE LOWER ELEVATIONS. AN UPPER LOW PRESSURE
SYSTEM WILL DEVELOP OVER THE PACIFIC NORTHWEST AND SLIDE SOUTH INTO
THE CWA ON FRIDAY. THIS WILL TRANSPORT MORE UNSTABLE AIR INTO THE
CWA ON FRIDAY. AS A RESULT THERE WILL BE SHOWERS AND A SLIGHT CHANCE
FOR THUNDERSTORMS. THE LEAST LIKELY PLACE TOO RECEIVE THUNDERSTORMS
WILL BE OVER CENTRAL OREGON ON DAY 3. SLIGHT CHANCE TO CHANCE
THUNDERSTORMS WILL OCCUR ELSEWHERE...WITH THE GREATEST CHANCE OVER
THE NORTHERN BLUE MOUNTAINS AND WALLOWA COUNTY AND THE GRANDE RONDE
VALLEY ON FRIDAY. THE STRONGEST WINDS WILL BE IN THE LOWER COLUMBIA
BASIN AND ADJACENT VALLEYS...ESPECIALLY ON FRIDAY. 88

LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...AN UPPER LEVEL LOW WILL
MOVE SOUTHEAST ACROSS SOUTHEAST WASHINGTON AND EASTERN OREGON FRIDAY
NIGHT. INSTABILITY AND MOISTURE ASSOCIATED WITH THE LOW WILL TRIGGER
SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE CWA...WITH THE HIGHEST
POPS OVER THE EASTERN MOUNTAINS AND THE EAST SLOPES OF THE
WASHINGTON CASCADES DUE TO ENHANCEMENT BY OROGRAPHIC LIFT. AN UPPER
LEVEL RIDGE WILL BUILD OFF THE PACIFIC COAST SATURDAY AND SUNDAY.
THIS WILL KEEP THE AREA UNDER NORTH TO NORTHWEST FLOW DURING THE
REST OF THE LONG TERM PERIOD. SATURDAY AND SUNDAY A SERIES OF WEAK
WAVES WILL MOVE DOWN THE BACKSIDE OF THE RIDGE. DAYTIME
HEATING...INSTABILITY...AND LINGERING MOISTURE MAY COMBINE TO
TRIGGER A FEW SHOWERS OVER THE BLUE MOUNTAINS AND EAST SLOPES OF THE
WASHINGTON CASCADES DURING THE AFTERNOON AND EVENING. MONDAY AND
TUESDAY A DRY AND WARMER CONDITIONS WILL BUILD INTO THE PACIFIC
NORTHWEST DUE TO SUBSIDENCE ASSOCIATED WITH THE RIDGE.  COONFIELD

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  83  53  81  53 /   0   0   0  10
ALW  83  60  81  59 /   0  10   0  10
PSC  86  59  84  58 /   0   0   0  10
YKM  84  52  80  54 /   0   0   0  10
HRI  85  57  84  56 /   0   0   0   0
ELN  82  56  80  55 /   0   0   0  10
RDM  76  41  75  43 /   0   0   0   0
LGD  79  47  78  49 /  10  10   0  10
GCD  78  47  77  50 /  10  10   0  10
DLS  81  56  80  58 /   0   0   0  10

&&

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

&&

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

$$

91/99/88/76





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