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000
FXUS66 KPDT 182231 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
330 PM PDT SAT MAY 18 2013

UPDATED AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...A WEAK PACIFIC SYSTEM
WILL CONTINUE TO MOVE ACROSS THE REGION TONIGHT. THIS SYSTEM WILL
THEN SHIFT SOUTHEAST ACROSS IDAHO AND WYOMING ON SUNDAY. WILL
CONTINUE TO SEE ISOLATED TO SCATTERED SHOWERS ACROSS MUCH OF THE
AREA THIS EVENING, WITH THE BEST CHANCES ACROSS CENTRAL AND
EAST-CENTRAL OREGON. THESE SHOWERS WILL GRADUALLY DECREASE LATE THIS
EVENING AND OVERNIGHT, WITH ONLY A FEW SHOWERS LINGERING OVER THE
MOUNTAINS TOWARDS DAYBREAK. THERE REMAINS ENOUGH INSTABILITY LATE
THIS AFTERNOON INTO EARLY THIS EVENING FOR STRAY THUNDERSTORMS OVER
THE SOUTHERN OREGON BLUE MOUNTAINS, THE JOHN DAY BASIN AND THE JOHN
DAY-OCHOCO HIGHLANDS. WINDS WILL CONTINUE BREEZY TO LOCALLY WINDY
ACROSS THE AREA THROUGH THIS EVENING, THEN GRADUALLY DECREASE
OVERNIGHT. LOCALLY BREEZY WINDS WILL CONTINUE THROUGH SUNDAY,
PRIMARILY IN AND NEAR THE COLUMBIA RIVER GORGE AND IN THE KITTITAS
VALLEY. LINGERING MOISTURE COMBINED WITH A NORTHWEST FLOW ALOFT WILL
KEEP A FEW SHOWERS GOING OVER SOME AREA MOUNTAINS SUNDAY THROUGH
SUNDAY EVENING DUE TO UPSLOPE AFFECTS. OTHERWISE HIGH PRESSURE ALOFT
AND AT THE SURFACE WILL BUILD INTO THE REGION SUNDAY NIGHT INTO
MONDAY. THUS EXPECT DRY CONDITIONS LATE SUNDAY NIGHT THROUGH MONDAY
EVENING. HIGH TEMPS MONDAY WILL WARM 7-10 DEGREES OVER SUNDAY
AFTERNOON. AN APPROACHING PACIFIC SYSTEM MAY SPREAD SOME LIGHT
PRECIP TO THE WASHINGTON CASCADE CREST AREA LATE MONDAY NIGHT,
OTHERWISE SHOULD CONTINUED DRY CONDITIONS WITH INCREASING CLOUDS. 90

.LONG TERM...TUESDAY THROUGH SATURDAY. CONFIDENCE IS HIGH THAT THE
PACIFIC NW WILL BE UNDER THE INFLUENCE OF A LARGE CLOSED LOW DURING
THE PERIOD.  HOWEVER...CONFIDENCE IN THE EXACT PLACEMENT OF THE LOW
AND THE LOCATION/STRENGTH OF EMBEDDED SHORTWAVES IS LOW...ESPECIALLY
THURS-SAT. THE LARGE UPPER LOW WILL MOVE ONSHORE TUESDAY THEN WILL
BECOME BLOCKED BY AN AMPLIFIED RIDGE OVER THE MIDWEST.  THIS COLD
LOW WILL RESULT IN UNSEASONABLY COLDER TEMPERATURES AND SHOWERY
CONDITIONS THROUGH THE EXTENDED PERIOD.  SNOW LEVELS WILL LOWER
SIGNIFICANTLY LATE TUESDAY NIGHT AND WEDNESDAY MORNING...POSSIBLY AS
LOW AS 3500-4000 FEET.  MODELS BEGIN TO DIVERGE ON THURSDAY.  WHILE
THE ECMWF SWINGS THE LOW TO THE NORTHEAST ACROSS OREGON ON
FRIDAY...THE GFS IS FARTHER NORTH AND WEST WITH THE PRIMARY POSITION
OFFSHORE. EITHER WAY...THE PACIFIC NW WILL BE COOL AND SHOWERY
DURING THE LONG TERM PERIOD.  WISTER

&&

.AVIATION...00Z TAFS. SCATTERED SHOWERS MAY CAUSE CIGS/VSBYS TO
BRIEFLY LOWER TO NEAR MVFR THIS AFTERNOON AND EVENING.
OTHERWISE...VFR CONDITIONS WILL PREVAIL FOR THE NEXT 24 HOURS. CIGS
WILL RANGE FROM 4-8000 FEET AGL...ALTHOUGH THERE WILL BE BREAKS IN
THE CLOUD COVER OVERNIGHT. SKIES WILL BE SCT-BKN ON SUNDAY WITH
BASES AROUND 7-10,000 FEET AGL. SUSTAINED WINDS OF 10-15 KNOTS
GUSTING TO 25 KNOTS CAN BE EXPECTED IN MOST AREAS THIS
EVENING...DIMINISH OVERNIGHT...THEN INCREASE TO 5-15 KNOTS ON
SUNDAY. WISTER

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  46  70  44  76 /  20  10   0   0
ALW  50  71  49  77 /  20  10   0   0
PSC  48  77  42  80 /  10  10   0   0
YKM  42  74  40  78 /  10  10   0   0
HRI  48  75  41  79 /  20  10   0   0
ELN  46  72  43  78 /  10  10   0   0
RDM  35  67  32  76 /  20  10   0   0
LGD  44  65  40  73 /  20  20   0   0
GCD  40  67  36  76 /  30  10   0   0
DLS  50  71  44  81 /  20  10   0   0

&&

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

THREAT INDEX
SUNDAY : GREEN
MONDAY : GREEN
TUESDAY : GREEN

GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.

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

$$

90/85/85