000
FXUS66 KPDT 201006
AFDPDT

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

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...AN UPPER LEVEL RIDGE
WILL MOVE OVER EASTERN WASHINGTON AND OREGON TODAY. THIS WILL KEEP
THE CWA MOSTLY CLEAR AND WARMER...THOUGH SOME CIRRUS MAY MOVE
THROUGH THE AREA. TUESDAY A DEEP UPPER LEVEL LOW WILL MOVE FROM THE
GULF OF ALASKA TO THE OREGON COAST...THEN SLIDE EAST OVERNIGHT. THIS
SYSTEM WILL BRING A COLD FRONT THROUGH EASTERN WASHINGTON AND OREGON
TUESDAY AFTERNOON. THE FRONT WILL BRING INCREASING WINDS, SHOWERS
AND FALLING TEMPERATURES. A FEW THUNDERSTORMS MAY DEVELOP AHEAD OF
THE FRONT FROM GRANT COUNTY TO THE BLUE MOUNTAINS AND WALLOWA COUNTY
AS WELL. AS THE UPPER LEVEL LOW MOVES EAST TUESDAY NIGHT SNOW LEVELS
WILL DROP TO 3-5 KFT. LOWEST SNOW LEVELS AND HIGHEST QPF AMOUNTS
WILL BE NEAR THE LOW OVER CENTRAL OREGON TO THE OCHOCO JOHN DAY
HIGHLANDS. GFS ENSEMBLES STILL SHOW SOME SPREAD IN THE LOCATION OF
THE LOW WEDNESDAY MORNING EVEN THOUGH IT IS ONLY A 60 HOUR FORECAST.
SINCE THE LOCATION OF THE HEAVIER PRECIPITATION BANDS DEPENDS ON THE
LOW AND VORTICITY ROTATING AROUND IT THERE IS SOME UNCERTAINTY WHERE
THEY WILL BE LOCATED.  COONFIELD

.LONG TERM...WEDNESDAY THROUGH SUNDAY...A LARGE MID/UPPER LEVEL LOW
WILL LINGER OVER THE FORECAST AREA THROUGH FRIDAY AND THEN LIFT
NORTHWARD INTO CANADA 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
WITH AN UPPER LOW ALONG THE COAST ON SUNDAY. SNOW LEVELS WILL BE LOW
ENOUGH WEDNESDAY AND WEDNESDAY NIGHT FOR A CHANCE OF SNOW IN THE
MOUNTAINS. MARGINAL DAYTIME INSTABILITY EACH AFTERNOON ON THURSDAY
AND FRIDAY WILL PRODUCE ISOLATED THUNDERSTORMS OVER THE EASTERN
MOUNTAINS.  POLAN

&&

.PREVIOUS AVIATION DISCUSSION...06Z TAFS. CLEAR SKIES TONIGHT WITH
SOME THIN CIRRUS ON MONDAY. SURFACE WINDS 5-15KT.  94

&&

.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  79  49  65  44 /   0   0  40  60
RDM  74  44  61  29 /   0   0  20  50
LGD  76  47  71  39 /   0   0  30  50
GCD  77  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

$$

76/99/99