Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 282143
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
243 PM PDT THU APR 28 2016

.SHORT TERM...TONIGHT THROUGH SUNDAY...FORECAST AREA CONTINUES TO BE
UNDER THE INFLUENCE OF A LARGE SCALE UPPER LEVEL TROUGH OVER THE
WESTERN U.S.. INSTABILITY SHOWERS ARE STARTING TO DEVELOP ACROSS
PORTIONS OF THE FORECAST AREA THIS AFTERNOON. THESE SHOWERS WILL
CONTINUE INTO THE EVENING AND THEN DECREASE AFTER SUNSET. A
SHORTWAVE DROPPING INTO THE TROUGH FROM THE GULF OF ALASKA WILL PASS
OVER THE REGION ON FRIDAY THEN DROP INTO THE GREAT BASIN OVERNIGHT
AND SATURDAY. WILL SEE AN INCREASE IN SHOWERS AND BREEZY WESTERLY
WINDS ON FRIDAY AS THIS SYSTEM DESTABILIZES THE ATMOSPHERE. HIGH
PRESSURE WILL BEGIN BUILDING INTO THE REGION FROM THE WEST SATURDAY
AND SUNDAY. THIS WILL LEAD TO A WARMING TREND AND DRY CONDITIONS
THROUGH THE WEEKEND.

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...SUNDAY NIGHT I CHOSE TO
KEEP DRY CONDITIONS IN FORECAST DESPITE SOME SUGGESTION IN THE
CANADIAN AND THE ECMWF 12Z MODEL RUNS THAT A SMALL SCALE SHORT WAVE
MOVES WEST ACROSS LOWER COLUMBIA BASIN AROUND THE BOTTOM OF A
MID/UPPER LEVEL RIDGE OF HIGH PRESSURE PARKED OVER BRITISH COLUMBIA
AND PACIFIC NORTHWEST. GFS 12Z RUN DOES NOT SHOW THE AFOREMENTIONED
SHORT WAVE. MONDAY DRY CONDITIONS CONTINUE DUE TO THE RIDGE STAYING
OVER PACIFIC NORTHWEST. MONDAY NIGHT DRY CONDITIONS PERSIST BY
VIRTUE OF THE RIDGE HOLDING FAST OVER THE ROCKIES AND THE FORECAST
AREA. TUESDAY A LONG WAVE MID/UPPER LEVEL TROUGH APPROACHES THE
COAST WHILE THE RIDGE AXIS NUDGES EAST A TAD, THUS ALLOWING THE
BROAD SOUTHERLY FLOW ALOFT ON THE EASTERN FLANK OF THE TROUGH TO
BEGIN TRANSPORTING MOISTURE INTO REGION THUS YIELDING INCREASING
POPS OVER THE CASCADES FOR A CHANCE OF SHOWERS IN HIGHER TERRAIN OF
THE CASCADES DURING THE DAY ON TUESDAY WITH A SLIGHT CHANCE OF
THUNDERSTORMS ALONG THE EAST SLOPES OF THE OREGON CASCADES TUESDAY
EVENING. WITH INCREASING MID LEVEL MOISTURE TUESDAY NIGHT, THE
REGION BECOMES UNSTABLE FOR AN INCREASING CHANCE OF SHOWERS
WEDNESDAY AND THURSDAY ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS
BOTH DAYS. SOME STRAY NIGHT-TIME THUNDERSTORMS WILL ALSO BE POSSIBLE
WEDNESDAY NIGHT AND THURSDAY EVENING OVER THE ENTIRE FORECAST AREA.
POLAN


&&

.AVIATION...00Z TAFS...VFR CONDITIONS WILL OCCUR AT ALL TAF SITES
FOR THE NEXT 24 HOURS. A MOIST NORTHERLY FLOW ALOFT WILL KEEP MOSTLY
CLOUDY SKIES WITH CIGS MAINLY BETWEEN 4000 AND 11000 FT AGL, EXCEPT
AT KYKM AND KDLS WHERE CLOUD BASES WILL BE SCT-BKN 8000 TO 10000 FT
AGL. SCATTERED SHOWERS IN VICINITY OF KALW AND KPDT AFTER 29/05Z.
WINDS WILL BE MAINLY LESS THAN 14 KTS, EXCEPT AT KDLS WHERE W-NW
WINDS OF 15 TO 20 KTS WITH HIGHER GUSTS THIS AFTERNOON AND THIS
EVENING.  POLAN


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  46  61  44  68 /  10  30  30  10
ALW  48  63  46  69 /  20  30  30  10
PSC  47  67  45  75 /  10  20  20  10
YKM  43  65  43  75 /  20  20  20   0
HRI  48  65  45  73 /  10  20  20   0
ELN  44  60  44  72 /  30  20  20   0
RDM  34  57  34  65 /  10  30  20   0
LGD  41  55  39  62 /  20  40  40  10
GCD  39  55  39  62 /  10  50  40  10
DLS  48  62  45  74 /  10  20  20   0

&&

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

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

$$

91/99/99


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