Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 262236
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PST FRI DEC 26 2014

.SHORT TERM...TONIGHT THROUGH SUNDAY. UPPER RIDGE CURRENTLY OVER THE
AREA WITH NORTHWEST FLOW ALOFT. EXPECT INCREASING CLOUDS THIS
EVENING AND OVERNIGHT. A WEATHER SYSTEM WILL MOVE THROUGH THE REGION
SATURDAY AND SUNDAY. MAIN IMPACTS WILL BE SIGNIFICANT SNOW
ACCUMULATIONS FOR THE MOUNTAINS. THE WASHINGTON CASCADES AND
NORTHEAST OREGON MOUNTAINS WILL SEE THE HIGHEST SNOWFALL TOTALS.
ADVISORIES AND WARNINGS HAVE BEEN ISSUED. LOWER ELEVATIONS WILL HAVE
MOSTLY RAIN AS TEMPERATURES WILL BE IN THE 30S TO LOWER 40S.
SURFACE GRADIENTS AND WINDS ALOFT WILL CREATE BREEZY CONDITIONS
SATURDAY. 94

.LONG TERM...SUNDAY NIGHT THROUGH TUESDAY NIGHT. A LARGE UPPER
TROUGH IS OVER THE AREA SUNDAY NIGHT WITH LOW PRESSURE SYSTEM
MOVING THROUGH THE TROUGH LATE SUNDAY NIGHT AND MONDAY WITH COLD AIR
SPREADING SOUTH AND A CHANCE OF SNOW ACROSS MOST OF THE AREA.  THE
UPPER LEVEL TROUGH SWINGS SOUTH ON TUESDAY WITH WITH DRY BUT VERY
COLD CONDITIONS FOR TUESDAY AND TUESDAY NIGHT. 93

WEDNESDAY THROUGH FRIDAY NIGHT...A STRONG MID/UPPER LEVEL RIDGE OF
HIGH PRESSURE WILL BE PARKED FROM 130W-140W WEDNESDAY AND WEDNESDAY
NIGHT. THIS PUTS THE FORECAST AREA ON THE EASTERN FLANK OF THE RIDGE
AND THUS IN A NORTHERLY FLOW ALOFT FOR DRY CONDITIONS. THE FLOW
ALOFT BEGINS BACKING TO THE NORTHWEST THURSDAY IN RESPONSE TO A
MID/UPPER LEVEL SHORT WAVE MOVING SOUTH-SOUTHEAST DOWN THE EASTERN
FLANK OF THE RIDGE. THURSDAY NIGHT THE SHORT WAVE MOVES ACROSS
BRITISH COLUMBIA. THE ECMWF IS A TAD FASTER THAN THE GFS IN TAKING
THE SHORT WAVE INTO FAR NORTHERN WASHINGTON BY DAYBREAK ON FRIDAY.
DURING THE DAY ON FRIDAY MID/UPPER LEVEL DIFLUENT FLOW AHEAD IF THE
SHORT WAVE INTRODUCES DYNAMIC LIFT WHICH YIELDS SNOW LIKELY IN THE
MOUNTAINS AS WELL AS IN CENTRAL AND NORTH CENTRAL OREGON AND THE
FOOTHILLS OF THE BLUE MOUNTAINS AND A CHANCE OF SNOW ACROSS THE
LOWER COLUMBIA BASIN AND THE KITTITAS AND YAKIMA VALLEYS. BOTH
MODELS ARE IN FAIRLY GOOD AGREEMENT IN MOVING THE SHORT WAVE ACROSS
THE FORECAST AREA FRIDAY NIGHT AND SATURDAY. THE SHORT WAVE WILL
PUSH A COLD FRONT INTO THE REGION FRIDAY NIGHT. SEVERAL FACTORS,
NAMELY DYNAMIC LIFT, OROGRAPHIC LIFT OVER THE NORTHEAST OREGON
MOUNTAINS AND FLOW ALOFT PARALLEL TO THE FRONT WILL PRODUCE
WIDESPREAD SNOW FRIDAY NIGHT, ESPECIALLY IN THE OREGON PORTION OF
THE FORECAST AREA RESULTING IN LIKELY POPS FOR SNOW FRIDAY NIGHT.
POLAN

&&

.AVIATION...00Z VFR CONDITIONS WILL CONTINUE UNTIL 12Z. MID AND
HIGH LEVEL CLOUDS WILL BEGIN TO INCREASE OVERNIGHT AS ANOTHER LOW
PRESSURE SYSTEM APPROACHES WITH SOME MVFR CEILINGS AND LIGHT RAIN AT
KYKM...KPSC...KALW AND KPDT AFTER 12Z. KDLS SHOULD SEE MVFR
CEILING AND LIGHT RAIN AFTER 15Z. WHILE KBND AND KRDM WILL SEE
LIGHT SNOW AND MVFR CEILINGS AFTER 18Z.  WINDS WILL REMAIN LIGHT
BELOW 10 KTS. 93

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  28  43  31  38 /  10  70  60  40
ALW  30  44  32  38 /  10  70  70  40
PSC  28  42  31  41 /  10  40  30  20
YKM  27  39  28  39 /  10  40  30  20
HRI  28  43  33  42 /   0  60  30  20
ELN  26  38  26  37 /  10  60  30  20
RDM  22  41  26  36 /   0  40  30  20
LGD  23  34  28  34 /  10  90  90  80
GCD  19  39  26  36 /   0  70  80  60
DLS  33  43  33  43 /  10  60  40  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY FROM 10 AM SATURDAY TO 10 AM PST SUNDAY
     ORZ505-506.

     WINTER STORM WARNING FROM 7 AM SATURDAY TO 10 AM PST SUNDAY
     ORZ049-050-502-503.

     WINTER WEATHER ADVISORY FROM 10 AM SATURDAY TO 10 AM PST SUNDAY
     ORZ509.

WA...WINTER STORM WARNING FROM 7 AM SATURDAY TO 10 AM PST SUNDAY
     WAZ030.

     WINTER STORM WARNING FROM 4 AM SATURDAY TO 4 AM PST SUNDAY
     WAZ520.

&&

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

$$

94/93/99/93




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