000
FXUS66 KPDT 062317 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
316 PM PST FRI DEC 6 2013

UPDATED AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...NUMEROUS WINTER
WARNINGS AND ADVISORIES ARE IN EFFECT MAINLY ACROSS OREGON FOR
TONIGHT INTO SATURDAY MORNING. A LOW PRESSURE SYSTEM WILL MOVE FROM
OREGON INTO THE CENTRAL PLAINS OVER THE WEEKEND. AS THIS
OCCURS...VERY COLD AIR WILL BE DRAWN SOUTHWARD ACROSS THE FORECAST
AREA ON NORTHERLY FLOW. THIS WILL BRING THE COLDEST AIR OF THE EARLY
WINTER SEASON ALONG WITH LOW WIND CHILLS. EXPECT SNOW TO SPREAD
EASTWARD TONIGHT MAINLY FROM THE OREGON/WA BORDER SOUTHWARD AND DUE
TO HIGH SNOW TO LIQUID RATIOS...SEVERAL INCHES OF ACCUMULATION ARE
EXPECTED. NORTH TO NORTHWEST UPSLOPE FLOW WILL ALSO ENHANCE SNOW
ACCUMULATIONS. IT WILL BE VERY COLD TONIGHT WITH LOWS SINGLE DIGITS
ABOVE ZERO TO ABOUT 10 BELOW ZERO. SNOW WILL TAPER OFF ON SATURDAY
WITH CONTINUED VERY COLD TEMPERATURES AND WIND CHILLS. ALTHOUGH THE
WINDS WILL DIMINISH SATURDAY NIGHT...ANY BREEZE WILL EXACERBATE THE
BITTERLY COLD TEMPERATURES WITH LOWS OF 0-20 BELOW ZERO. ON SUNDAY
TEMPERATURES WILL WARM UP TO THE TEENS MOST AREAS WITH JUST A SLIGHT
CHANCE OF SNOW SHOWERS EAST. SUNDAY NIGHT WILL BE PARTLY CLOUDY AND
COLD BUT NOT AS COLD AS SUNDAY MORNING. 78

.LONG TERM...MONDAY THROUGH WEDNESDAY...MODELS IN GOOD AGREEMENT
WITH RESPECT TO UPPER RIDGE BRINGING DRY...NORTHERLY FLOW OVER THE
REGION MONDAY. HOWEVER...THEY BEGIN TO DIVERGE TUESDAY AS ECMWF
SHOWS A MORE AMPLIFIED RIDGE MOVING OVER THE PACIFIC NORTHWEST. WITH
ITS MORE AMPLIFIED PATTERN...IT MOVES THE RIDGE MORE SLOWLY OVER OUR
FORECAST AREA RESULTING IN CONTINUED DRY WEATHER...EXCEPT ALONG THE
WASHINGTON CASCADES. GFS IS LESS AMPLIFIED AND MORE PROGRESSIVE WITH
ITS SOLUTION. IF CORRECT...IT WOULD INDICATE A CHANCE OF SNOW OVER
OUR WESTERN CWA BY LATE WEDNESDAY AFTERNOON. GIVEN DISCREPANCIES AND
CONTINUED INCONSISTENCIES BETWEEN MODEL RUNS...BELIEVE BEST SOLUTION
IS TO GO ON THE DRY SIDE OF CLIMATOLOGY. TEMPERATURES WILL SLOWLY
WARM THROUGH THE PERIOD...ESPECIALLY OVER OUR SOUTHWEST FORECAST
AREA AS UPPER RIDGE BRINGS IN WARMER AIR FROM THE SOUTH. EARLE

WEDNESDAY NIGHT THROUGH FRIDAY...UNCERTAINTY BETWEEN MODELS AND
MODEL RUNS, AS MENTIONED ABOVE, CONTINUES WITHIN THIS PERIOD. THE
GFS CONTINUES TO BE MORE PROGRESSIVE WITH A LATE WEEK SYSTEM THAN
THE ECMWF, THOUGH THEY ARE BOTH HINTING AT THIS SYSTEM SPLITTING AS
IT MOVES ONSHORE. AS SUCH HAVE GONE WITH A COMPROMISE BETWEEN THESE
TWO MODELS AND LOWERED POPS WEDNESDAY NIGHT AND THURSDAY. WARMING
ALOFT IS NOW NOT LOOKING AS DRAMATIC AS IN PREVIOUS MODEL RUNS. THUS
THE CHANCES FOR FREEZING RAIN HAVE BECOME MORE UNCERTAIN. THEREFORE
HAVE REDUCED MENTION OF FREEZING RAIN TO SLIGHT CHANCE AND DECREASED
THE AREAL COVERAGE. HAVE ALSO INCLUDED A SLIGHT CHANCE OF SLEET TO
THE SAME AREAS WITH A MENTION OF FREEZING RAIN. SINCE THE WARM UP
ALOFT LOOKS TO BE LESS DRAMATIC, HAVE SLOWED THE SURFACE WARMING
WEDNESDAY NIGHT AND THURSDAY. 90

&&

.AVIATION...00Z TAFS...A WINTER STORM WILL CONTINUE TO BRING SNOW TO
MAINLY THE SOUTHERN HALF OF THE AREA TONIGHT. MVFR CONDITIONS DUE TO
SNOW AND CEILINGS WILL PERSIST THROUGH 07/06Z FOR KRDM...KBDN...KDLS
AND KPDT. PERIODS OF HEAVIER SNOW WILL PRODUCE IFR/LIFR CONDITIONS.
KALW...KPSC AND KYKM SHOULD GENERALLY REMAIN VFR. CLEARING FROM
NORTH TO SOUTH IS EXPECTED TO BEGIN LATE TONIGHT.  LIGHT WINDS WILL
INCREASE TO 10 TO 20 KTS THIS EVENING AT KDLS...KYKM KPSC AND KPDT.
ALL OTHER SITES SHOULD REMAIN LESS THAN 12 KTS. WINDS ARE EXPECTED
TO DECREASE SATURDAY AFTERNOON AS SURFACE HIGH PRESSURE SETTLES OVER
THE AREA.  EARLE

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT   4   9  -5  16 /  70  60   0  10
ALW   8  11   1  16 /  60  20   0  10
PSC   7  17  -3  18 /  10   0   0  10
YKM   5  18  -4  21 /  10   0   0  10
HRI   5  14  -6  16 /  40   0   0  10
ELN   4  20  -3  20 /  10   0   0  10
RDM  -5   8 -15  18 / 100  20   0  10
LGD  11   9  -4  11 /  70  60   0  10
GCD   8   9 -11  13 /  90  40   0  10
DLS  13  21   7  22 /  70  10   0  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY ORZ049-050.

     WIND CHILL WARNING FROM 7 PM THIS EVENING TO 10 AM PST SUNDAY
     ORZ041-044-049-050-502-503-505>511.

     WINTER STORM WARNING UNTIL 4 AM PST SATURDAY ORZ506-511.

     WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY ORZ507.

     WINTER STORM WARNING UNTIL 4 AM PST SATURDAY ORZ508-510.

     WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING ORZ503.

     WINTER STORM WARNING UNTIL 4 AM PST SATURDAY ORZ509.

     WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING ORZ041.

     WINTER STORM WARNING UNTIL 10 PM PST THIS EVENING ORZ505.

WA...WIND CHILL WARNING FROM 7 PM THIS EVENING TO 10 AM PST SUNDAY
     WAZ024-026>030-520-521.

     WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING WAZ024.

&&

THREAT INDEX
SATURDAY : YELLOW
SUNDAY : GREEN
MONDAY : 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

$$

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