Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 180220 CCA
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
712 PM PDT WED SEP 17 2014

.UPDATE...PRECIPITATION IS STAYING MOSTLY WEST OF THE CASCADES THIS
EVENING AS A PACIFIC WEATHER SYSTEM GETS READY TO MOVE INTO THE
REGION. THE ATMOSPHERE IS WARM AND DRY AND WINDS ARE A LITTLE
STRONGER THIS EVENING THAN DURING THE PAST FEW DAYS. UPPER TROUGH IS
FORECAST TO CROSS THE REGION ON THURSDAY WITH SOME WEAK INSTABILITY.
THEREFORE ALSO HAVE SOME THUNDERSTORMS MENTIONED IN THE FORECAST
FROM CENTRAL OREGON NORTHEAST ACROSS THE JOHN DAY HIGHLANDS AND THE
BLUE AND WALLOWA MOUNTAINS THURSDAY AFTERNOON AND EVENING.
PRECIPITATION AMOUNTS WILL BE VERY LIGHT AS SYSTEM SPLITS...AS IT
MOVES INLAND. CONDITIONS WILL DRY OUT AGAIN THURSDAY NIGHT AND
FRIDAY AS NEXT UPPER RIDGE BUILDS OVER THE REGION WITH ANOTHER
WARMING TREND WITH DRY CONDITIONS THROUGH THE WEEKEND. CURRENT
FORECAST IS ON TRACK. 88

&&

.AVIATION...06Z TAFS...VFR CONDITIONS ARE EXPECTED TO PERSIST
THROUGH THE NEXT 24 HOURS. THERE MAY BE SOME LIGHT SHOWERS AT
KDLS...KRDM...KBDN...KPDT AND KALW THURSDAY WITH POSSIBLY A
THUNDERSTORM AT KRDM AND KBDN THURSDAY AFTERNOON AND EVENING. WINDS
WILL BE GENERALLY LIGHT EXPECT POSSIBLY GUSTY AND ERRATIC NEAR ANY
THUNDERSTORMS. CIGS AND VISIBILITIES WILL REMAIN ABOVE VFR DUE TO
THE DRYNESS OF THE AIR IN THE LOW LEVELS THROUGH THURSDAY EVENING. 88

&&

.PREV DISC... /ISSUED 205 PM PDT WED SEP 17 2014/

SHORT TERM...TONIGHT THROUGH SATURDAY...UPPER LEVEL RIDGE OF HIGH
PRESSURE OVER THE REGION IS RETREATING TO THE EAST AS AN UPPER LEVEL
TROUGH SYSTEM APPROACHES THE COAST. ALREADY SEEING CLOUDS ASSOCIATED
WITH TROUGH PASSING OVER THE REGION BUT PRECIPTATION THUS FAR HAS
REMAINED WEST OF THE CASCADES. THE TROUGH WILL BE UNDERGOING A SPLIT
OVERNIGHT AND THURSDAY AS IT MOVES INLAND. THIS WILL WEAKEN THE
SYSTEM TO THE POINT THAT IS WILL MAINLY BE SOME CLOUDS BUT VERY LOW
CHANCE OF PRECIPITATION. WILL SEE SOME LIGHT PRECIPITATION APPROACH
THE CASCADES OVERNIGHT OF WHICH SOME COULD SPREAD ONTO THE EAST
SIDE. ALSO WATCHING FOR SOME CONVECTION TO FORM OVER SOUTHEAST
OREGON OVERNIGHT WHICH COULD CLIP THE FAR EASTERN ZONES. THE TROUGH
PASSAGE ON THURSDAY WILL BE MARKED WITH MAINLY CLOUDS AND LOW CHANCE
OF PRECIPITATION. MODELS DO INDICATE SOME WEAK INSTABILITY SO
CARRYING A SLIGHT CHANCE OF THUNDERSTORMS BUT OVERALL THE SYSTEM
LOOKS UNIMPRESSIVE. FRIDAY AND SATURDAY WILL SEE THE RETURN OF A
BUILDING RIDGE HIGH PRESSURE OVER THE REGION WITH TEMPERATURES ONCE
AGAIN IN THE MID 80S ACROSS THE LOWER BASIN BY SATURDAY.

LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS IN GOOD
AGREEMENT WITH RESPECT TO DOMINANT RIDGE OVER THE WEEKEND.
HOWEVER...GFS IS FASTER IN PUSHING IT EAST AS THE NEXT TROUGH
APPROACHES. AT THIS TIME...GOING TO LEAN TOWARDS ECMWF AS IT IS
SLOWER AT MOVING THE RIDGE EAST AND SEEMS TO HAVE A LITTLE MORE RUN
TO RUN CONSISTENCY.  AS A RESULT...THE WEATHER SHOULD REMAIN
GENERALLY DRY THROUGH MONDAY.  HOWEVER..COULD SEE SOME WRAPAROUND
MOISTURE IN OUR EXTREME SOUTHEAST CWA AS AN UPPER LOW MOVES THROUGH
NORTHERN NEVADA SUNDAY AND MONDAY.  AT THIS TIME...EXPECT ONLY AN
INCREASE IN CLOUD OVER...BUT WILL HAVE TO WATCH CLOSELY ON FINAL
TRACK OF SYSTEM.  BY TUESDAY...MODELS IN FAIR AGREEMENT WITH
SOUTHWEST FLOW OVER THE REGION.  THIS COULD BRING A SLIGHT CHANCE OF
SHOWERS OVER FAVORED MOUNTAIN LOCATIONS.  BY WEDNESDAY...A DEEP
UPPER LEVEL TROUGH APPROACHES THE REGION PROVIDING A CHANCE OF
SHOWERS AREA WIDE. THERE ARE DISCREPANCIES BETWEEN MODELS IN THE
STRENGTH AND PATH OF THE TROUGH SO WENT WITH A MIX BUT STAYING ABOVE
CLIMATOLOGY.  IF WE ARE LUCKY...IT COULD BE OUR FIRST WETTING RAIN
IN QUITE SOME TIME.  TEMPERATURES WILL BE ABOVE NORMAL THIS WEEKEND
BUT SLOWLY COOL TO NEAR NORMAL BY THE END OF THE PERIOD.  EARLE

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  58  81  58  80 /   0  20  10   0
ALW  63  81  61  80 /   0  20  10   0
PSC  57  84  58  83 /   0  10  10   0
YKM  57  79  54  82 /  10  10  10   0
HRI  57  83  58  83 /   0  10  10   0
ELN  55  78  57  81 /  10  20  10   0
RDM  51  75  45  78 /  10  20  20   0
LGD  54  80  51  76 /  10  20  20   0
GCD  50  78  49  78 /  10  20  20   0
DLS  62  80  59  84 /  10  20  10   0

&&

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

&&

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

$$

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