Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 231700 AAA

Area Forecast Discussion
National Weather Service Pendleton OR
900 AM PST Thu Feb 23 2017

Updated Aviation Discussion

.UPDATE...A broad trough of low pressure will remain over the
Pacific Northwest for the next several days. A weak shortwave
will rotate around the trough later today...providing for
isolated/scattered PoPs mainly across the mountains and Central
Oregon. Snow levels will generally be in the 750-1500 ft range
so expect the bulk of the precip to be snow...with little
accumulation expected. Lower elevation locations will experience
partly cloudy skies. With the flow becoming more
northerly...expect high temperatures to be somewhat cooler than
yesterday...with readings in the upper 30s/around 40 for the
lower elevations and lower/mid 30s for the mtns.


.AVIATION...18Z TAFs...VFR conditions and light winds are expected
the next 24 hours. At KRDM and KBDN...CIGS 3500-5000 feet this
morning will decrease to SCT mid level clouds during the afternoon
and evening.  Elsewhere...SCT-BKN clouds with bases AOA 7000 feet.


.PREV DISCUSSION... /issued 300 AM PST Thu Feb 23 2017/

SHORT TERM...Today through Saturday...A trough will remain over the
Pacific Northwest for the next few days and will keep below normal
temperatures and showery conditions over the area with snow levels
below 1000-1500 feet. Today a cold north to northwesterly flow will
keep a chance of mainly snow showers in the mountains and Central
Oregon, possibly mixed with rain showers in the afternoon. The
Columbia Basin, Blue Mountain Foothills and Yakima and Kittitas
Valleys will remain dry. Moisture is limited so precipitation
amounts will be just a few hundredths of an inch or less than a half
inch of snow today. Showers will drop off rapidly in the evening and
tonight any snow showers will be confined to the Cascades and
Wallowa mountains. Friday an upper low will slide out of the
Canadian Rockies to just off the Washington coast by the afternoon
and then off the Oregon/Northern California coast by Saturday
morning. Friday will see a west to northwest flow before turning
northeast Friday night. Friday morning will just have a chance of
snow showers along the Cascade Crest with the rest of the area dry.
Friday afternoon and night, the northwest flow will keep a slight
chance of light snow showers, mixed with rain in the afternoon, over
much of the area though the Columbia Basin and Blue Mountain
Foothills will remain dry. Precipitation amounts will again be light
and snow amounts will be under an inch. Saturday the models show
ridging over the area though they differ as to the track of the low.
The ECMWF keeps the low off the Northern California coast while the
GFS weakens it and moves it to near Sacramento. Either way, very
light snow and rain showers will be confined to Central Oregon and
the Eastern Oregon mountains. Precipitation will be just a few
hundredths of an inch and less than a half inch of snow.
Temperatures will mainly be in the 30s today through Saturday with a
few lower 40s in the Columbia basin and a few upper 20s in the
higher mountain locations. Lows will be in the teens to lower 20s.

LONG TERM...Saturday night through Friday...Medium to long range
models are in good agreement that a series of upper troughs will
rotate around a large upper trough over the inland northwest and
that they will stay to the west and south of the forecast area. This
pattern will persist through about Wednesday and then an upper ridge
will develop off the coast. In the mean time the trough pattern will
keep colder than normal conditions over the CWA through the middle
of next week. Models do diverge from each other by the middle of
next week making timing of individual systems difficult. During this
period it will be cold enough for mainly snow at night but then
during the day snow levels will rise high enough to cause mixed rain
and snow in the lower elevations. In any case there could be
significant snow accumulations in the mountains...with some snow
possible in the lower elevations. After Wednesday the long range
models all show an upper ridge building off the coast which will
cause a warming trend to take place with temperatures rebounding
back to normal again as the ridge builds and moves into the Pacific
Northwest. It will be breezy to windy at times behind each system as
it moves through the region. 88


PDT  38  23  38  24 /  10   0  10  10
ALW  38  23  39  24 /  10   0  10  10
PSC  42  23  41  25 /   0   0  10  10
YKM  41  21  38  23 /  10  10  20  10
HRI  40  24  40  25 /   0   0  10  10
ELN  35  15  33  17 /  10  10  30  20
RDM  36  18  38  16 /  20  20  20  20
LGD  35  19  36  19 /  20  10  20  20
GCD  35  18  36  19 /  20  10  20  20
DLS  41  24  40  27 /  10  10  30  30




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