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000
FXUS66 KPDT 201601
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
901 AM PDT MON MAY 20 2013

.SHORT TERM...UPDATE...THE REGION WILL BE UNDER A TRANSITORY UPPER
LEVEL HIGH PRESSURE TODAY. THIS RIDGE WILL SLIDE EAST TONIGHT AS A
DEEP UPPER LOW MOVES TOWARD THE PACIFIC NORTHWEST FROM THE GULF OF
ALASKA. EXPECT DRY CONDITIONS TODAY WITH GENERALLY FAIR SKIES. SOME
CUMULUS CLOUDS WILL DEVELOP OVER THE MOUNTAINS LATE MORNING THROUGH
THE AFTERNOON. WILL SEE INCREASING MID AND HIGH LEVEL CLOUDINESS
THROUGH TONIGHT. WINDS WILL BE MOSTLY LESS THAN 15 MPH THROUGH
TONIGHT. WILL SEE A GOOD WARM UP TODAY WITH LOW ELEVATION HIGHS
RUNNING FROM THE LOW 70S TO AROUND 80. UPDATES THIS MORNING WERE
MADE TO ADJUST SKY COVER, SOME HIGH TEMPS AND A FEW WIND DIRECTIONS.
90

.LONG TERM...PREVIOUS DISCUSSION...A LARGE MID/UPPER LEVEL LOW WILL
LINGER OVER THE FORECAST AREA THROUGH FRIDAY AND THEN LIFT NORTHWARD
INTO BRITISH COLUMBIA FRIDAY NIGHT FOLLOWED BY THE LOW REGROUPING
AND COMBINING WITH AN UPSTREAM MID/UPPER LEVEL SHORT WAVE MOVING
EAST TOWARD THE COAST ON SATURDAY. THE TWO SYSTEMS MERGE ON SUNDAY
RESULTING IN A MID/UPPER LEVEL LOW PARKED ALONG THE COAST ON SUNDAY.

SNOW LEVELS AROUND DAYBREAK WEDNESDAY MORNING WILL BE 3000-4000 FT
RISING TO 3500-4500 FT WEDNESDAY AFTERNOON AND CONTINUING 3500-4500
FT THROUGH WEDNESDAY NIGHT. THUS SNOW LEVELS WILL BE LOW ENOUGH
WEDNESDAY AND WEDNESDAY NIGHT FOR A CHANCE OF SNOW IN THE MOUNTAINS.
MARGINAL DAYTIME SURFACE HEATING WILL YIELD STEEP TEMPERATURE LAPSE
RATES FROM 5000-20000 FT OF 7-8 DEGREES CELSIUS THURSDAY AND
FRIDAY,  WHICH WILL PRODUCE AN UNSTABLE ATMOSPHERE IN THE AFTERNOON
ON THURSDAY AND FRIDAY. AS SUCH ISOLATED THUNDERSTORMS ARE POSSIBLE
OVER THE EASTERN MOUNTAINS IN THE AFTERNOON AND EARLY EVENING ON
THURSDAY AND FRIDAY. A MID/UPPER LEVEL SHORT WAVE ROTATING AROUND
THE SOUTHERN FLANK OF THE AFOREMENTIONED THE MID/UPPER LEVEL LOW
WILL MOVE INTO THE FORECAST AREA SUNDAY AND BRING DYNAMIC LIFT AND
INCREASING MID LEVEL MOISTURE, WHICH WILL COMBINE WITH DAYTIME
SURFACE HEATING LEADING TO MARGINAL INSTABILITY SUNDAY AFTERNOON FOR
A SLIGHT CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND EVENING IN THE
EASTERN MOUNTAINS OF OREGON.

&&

.AVIATION...PREVIOUS DISCUSSION...12Z TAFS...CLEAR SKIES THIS
MORNING GIVING WAY TO SCATTERED HIGH CLOUDS AT KDLS AND KYKM DUE TO
SOME THIN CIRRUS BY LATE THIS MORNING. INCREASING MID LEVEL CLOUDS
TONIGHT WITH CLOUD BASES NEAR 12000-15000 FT AGL. UPSLOPE WINDS 5-10
KTS BY LATE THIS MORNING BECOMING DRAINAGE WINDS 4-8 KTS BY EARLY
THIS EVENING.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  77  51  69  40 /   0   0  30  50
ALW  78  54  73  45 /   0   0  30  50
PSC  81  52  76  47 /   0   0  20  50
YKM  79  48  74  41 /   0   0  40  40
HRI  80  50  72  44 /   0   0  20  50
ELN  78  49  65  44 /   0   0  40  60
RDM  74  44  61  29 /   0   0  20  50
LGD  75  47  71  39 /   0   0  30  50
GCD  76  45  67  36 /   0   0  40  50
DLS  79  53  63  43 /   0   0  50  60

&&

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

THREAT INDEX
TODAY : GREEN
TUESDAY : GREEN
WEDNESDAY : 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

$$

90/99/89