Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 150333
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
833 PM PDT SUN SEP 14 2014

.UPDATE...TONIGHT THROUGH TUESDAY MORNING...UPPER LEVEL RIDGE
OVER THE AREA THIS EVENING WILL CONTINUE TO MOVE EAST OVERNIGHT.
THIS WILL ALLOW FOR CLEAR SKIES TO CONTINUE WITH OVERNIGHT
TEMPERATURES BEING ABOUT 3 TO 5 DEGREES WARMER COMPARED TO LAST
NIGHT. A CLOSED UPPER LOW LOCATED AT 38N/135W WILL APPROACH THE
COAST AND BECOME A NEGATIVELY TILTED TROUGH. THIS TROUGH WILL MOVE
NORTH UP THE OREGON AND WASHINGTON COAST MONDAY AFTERNOON AND
EVENING...WITH MID LEVEL MOISTURE AND INSTABILITY MOVING ACROSS
THE AREA MONDAY NIGHT INTO TUESDAY. THIS COULD RESULT IN ISOLD
MAINLY DRY THUNDERSTORMS IN CENTRAL OREGON MONDAY NIGHT SPREADING
NORTHEAST ACROSS THE OCHOCO HIGHLAND AND THE BLUE MOUNTAINS BY
MIDDAY TUESDAY. HAVE UPDATED THE POPS GRIDS TO HONE IN ON AREAS OF
ELEVATED INSTABILITY BASED UPON LATEST GUIDANCE. THE REST OF THE
FORECAST REMAINS ON TRACK.  BIEDA

&&

.PREV DISC... /ISSUED 335 PM PDT SUN SEP 14 2014/

..UPDATED AVIATION DISCUSSION...

SHORT TERM...TONIGHT THROUGH WEDNESDAY. HIGH PRESSURE THAT
DOMINATED THE AREAS WEATHER WITH DRY CONDITIONS WILL GIVE WAY TO AN
APPROACHING LOW PRESSURE SYSTEM MONDAY AFTERNOON. THE LOW PRESSURE
WILL MOVE NORTH ALONG THE OR COAST AND INSTABILITY WILL INCREASE
ACROSS CENTRAL OREGON MONDAY EVENING. THIS COULD RESULT IN ISOLD
TSRA WHICH MAY EXPAND INTO THE OCHOCO OVERNIGHT AND THEN DRIFT INTO
THE BLUE MOUNTAINS TUESDAY MORNING BEFORE MOVING AWAY TUESDAY
AFTERNOON. A RETURN TO DRY CONDITIONS IS LIKELY TUESDAY NIGHT BEFORE
A STORM SYSTEM NEARS THE WA/OR COAST WEDNESDAY INCREASING THE
CHANCES FOR SHOWERS AND TSRA ACROSS PORTIONS OF THE REGION.

ABOVE NORMAL HIGH TEMPERATURES ARE EXPECTED INTO THE MIDDLE OF THE
WEEK AND MAY APPROACH 90 DEGREES ACROSS PORTIONS OF THE BASIN.

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY. GFS, ECMWF AND CANADIAN
ARE IN GENERAL AGREEMENT WITH ANOTHER SHORTWAVE TROUGH OFFSHORE ON
WEDNESDAY NIGHT AND THURSDAY.  THIS WILL LEAVE THE FORECAST AREA
UNDER A S-SW FLOW ALOFT AND ABOUT A 20-40 PERCENT CHANCE OF SHOWERS
AND A SLIGHT CHANCE OF THUNDERSTORMS.  A DRY WESTERLY FLOW WILL
FOLLOW THURSDAY NIGHT AND FRIDAY.  HIGH PRESSURE IS THEN PROGGED TO
DEEPEN OVER WA/OR NEXT WEEKEND FOR A WARM AND DRYING TREND.
TEMPERATURES DURING THE EXTENDED WILL BE NEAR TO SLIGHTLY ABOVE
NORMAL.  WISTER

AVIATION...00Z TAFS...CLEAR SKIES AND LIGHT DRAINAGE WINDS WILL
PREVAIL TONIGHT.  THIN CIRRUS CLOUDS WILL SPREAD ACROSS THE REGION
EARLY MONDAY MORNING FOLLOWED BY SCATTERED CUMULUS AND ALTOCUMULUS
AOA 10,000 FEET MSL DURING THE DAY. WINDS WILL REMAIN LESS THAN 10
KNOTS ON MONDAY.  WISTER

FIRE WX...A LOW PRESSURE SYSTEM WILL APPROACH CENTRAL OREGON LATE
MONDAY AFTERNOON AND EVENING WHICH MAY PRODUCE ISOLD DRY TSRA THAT
COULD PRODUCE ABUNDANT LIGHTNING. THIS HAS RESULTED IN A FIRE
WEATHER WATCH FOR PORTIONS OF THE DESCHUTES NATIONAL FOREST MINUS
SISTERS RANGER DISTRICT FROM MONDAY AFTERNOON THROUGH MONDAY EVENING.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  50  87  58  87 /   0   0  10  10
ALW  54  87  61  87 /   0   0  10  10
PSC  49  87  53  87 /   0   0   0  10
YKM  47  85  53  86 /   0   0  10  10
HRI  47  89  54  89 /   0   0  10  10
ELN  48  87  52  88 /   0   0  10  10
RDM  41  87  47  85 /   0   0  10   0
LGD  46  87  55  88 /   0   0  20  20
GCD  48  87  57  88 /   0   0  20  20
DLS  53  92  56  86 /   0   0  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM MONDAY AFTERNOON THROUGH MONDAY EVENING
     ORZ509.

WA...NONE.
&&

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

$$

98/85/98





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