Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 271756 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
956 AM PST TUE JAN 27 2015

UPDATED AVIATION DISCUSSION

.UPDATE...HIGH PRESSURE CURRENTLY OVER THE AREA WILL BEGIN TO BREAK
DOWN TODAY AS A WEATHER SYSTEM FROM THE SOUTH AND A WEAK SYSTEM FROM
THE WEST COLLIDES WITH THE AREA.  OVERALL THE MODELS AGREE WITH
COLDER AIR ALOFT MOVING IN AND BREAKING THE INVERSION DOWN OVER THE
VALLEYS.  THE ISSUE IS THE TIMING OF THIS BREAK DOWN.  MOST MODELS
WANT TO MIX THINGS OUT ACROSS THE LOWER ELEVATIONS AND HAVE THE
TYPICAL COLD SPOTS LIKE PENDLETON...HERMISTON...YAKIMA...AND THE
TRI-CITIES WARM UP INTO THE UPPER 40S TO MID 50S.  WHILE THIS CAN
NOT BE NOT RULED OUT...CONFIDENCE IS VERY LOW THAT THE MIXING
WILL BE STRONG ENOUGH TO MAKE THIS HAPPEN.  OVERALL...HAVE GONE WITH
MOST AREAS ALONG THE FOOTHILLS MIXING OUT THIS EVENING AFTER
SUNSET...WHICH WOULD STILL WARM THEM UP A BIT...BUT MORE SO INTO THE
MID 40S.  AREAS ALONG THE SOUTHERN FOOTHILLS LIKE CONDON AND FOSSIL
WILL LIKELY BE MOSTLY CLEAR AND MILD AGAIN...SO LONG AS THE
FOG/STRATUS DECK DOES NOT EXPAND.  CENTRAL OREGON AND THE JOHN DAY
VALLEY SHOULD ALL BE MILD AS WELL AGAIN TODAY WITH PARTLY CLOUDY
SKIES.  THE WASHINGTON BASIN MAY IMPROVE...BUT THE CONFIDENCE IS
LOWEST FOR THIS AREA.  FORECASTING HIGH TEMPERATURES ARE VERY
DIFFICULT IN THESE SITUATIONS...AND LATE MORNING TO EARLY AFTERNOON
UPDATES MAY BE NEEDED...DEPENDING ON THE CHANGES.  WEBER

&&

.AVIATION...18Z TAFS...PATCHY LOW STRATUS AND FOG CONTINUE THIS
MORNING AT KDLS...KYKM...KPSC...KPDT AND KALW. THE LIFR/IFR CIGS AND
VIS ARE EXPECTED TO RISE AND BECOME BKN AFTER 20Z TODAY. IT APPEARS
KYKM MAY SEE THE FOG PERSIST THE LONGEST BUT EVEN HERE CONDITIONS
SHOULD SEE SOME IMPROVEMENT AFTER 20-22Z TODAY. AFTER  28/01-03Z AND
ESPECIALLY AFTER 28/10Z GUIDANCE IS INDICATING THE POTENTIAL FOR
LOWERING CIGS/VIS AGAIN AT MOST TERMINALS(EXCEPT KRDM AND KBDN) BACK
INTO THE IFR OR PERHAPS LIFR CATEGORY. AT KBDN AND KRDM EXPECT JUST
MID TO HIGH LEVEL CLOUDS MAINLY BETWEEN 5K TO 15K FEET AGL THROUGH
THE PERIOD. WINDS ARE FORECAST TO REMAIN LIGHT AOB 10KTS THROUGH THE
NEXT 24 HOURS. 77

.PREV DISC... /ISSUED 349 AM PST TUE JAN 27 2015/

SHORT TERM...TODAY THROUGH THURSDAY AFTERNOON...INCREASING MID AND
UPPER LEVEL CLOUDS STREAMING THROUGH THE MID/UPPER LEVEL RIDGE
TODAY AS A RESULT OF A WEAK UPPER LEVEL DISTURBANCE MOVING THROUGH
THE RIDGE. MEANWHILE THE LOW STRATUS CLOUDS AND FOG WILL PERSIST
ACROSS THE LOWER COLUMBIA BASIN. A DENSE FOG ADVISORY REMAINS IN
EFFECT UNTIL NOON TODAY FOR THE LOWER COLUMBIA BASIN, ADJACENT
VALLEYS AND THE FOOTHILLS OF THE BLUE MOUNTAINS. EXPECT LITTLE
SCOURING OUT OF THE LOW CLOUDS AND FOG. ANOTHER VERY WEAK SYSTEM
MOVES THROUGH THE FORECAST AREA WEDNESDAY NIGHT AND THURSDAY FOR A
SLIGHT CHANCE OF RAIN IN THE BLUE MOUNTAINS AN WALLOWA COUNTY.
POLAN

LONG TERM...THURSDAY NIGHT THROUGH MONDAY...UPPER LEVEL HIGH
PRESSURE WILL LINGER OVER THE REGION THURSDAY NIGHT INTO SATURDAY.
THUS EXPECT MAINLY DRY CONDITIONS. ALSO FOG AND LOW CLOUDINESS WILL
CONTINUE TO IMPACT LOWER ELEVATIONS AREAS (GENERALLY BELOW 3000 FT
MSL) AND A FEW HIGH ELEVATION VALLEYS. HIGH TEMPS ABOVE 3000 FT WILL
CONTINUE MILD, BUT HIGH TEMPS BELOW 3000 FT WILL BE SEASONALLY COOL.
PACIFIC SYSTEMS LOOK TO FLATTEN THE RIDGE SUNDAY INTO MONDAY. THUS
EXPECT CHANCES FOR PRECIPITATION TO RETURN TO THE REGION. AT THIS
TIME SNOW LEVELS LOOK TO LOWER TO BETWEEN 2500 AND 4000 FT MSL
OVERNIGHT, BUT SHOULD BE A BIT HIGHER DURING THE LATE MORNING AND
AFTERNOON SUNDAY AND MONDAY. SHOULD SEE SOME INCREASE IN WINDS
ACROSS THE BASIN BY MONDAY. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  35  40  35 /  10   0   0  10
ALW  47  35  41  35 /  10  10  10  10
PSC  44  34  42  35 /  10   0   0  10
YKM  38  30  38  33 /  10  10   0   0
HRI  40  35  42  36 /  10  10   0  10
ELN  46  32  39  33 /  10  10   0  10
RDM  60  34  55  33 /   0   0  10  10
LGD  52  36  49  31 /   0  10  10  10
GCD  54  35  51  34 /  10  10  10  10
DLS  54  38  45  39 /  10  20  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...DENSE FOG ADVISORY UNTIL NOON PST TODAY ORZ041-044-507-508-510.

WA...DENSE FOG ADVISORY UNTIL NOON PST TODAY WAZ024-026>029-521.

&&

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

$$

89/90/77






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