Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 181734 AAA

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1034 AM PDT Sun Mar 18 2018

Updated aviation discussion

.SHORT TERM...Today and tonight...The main upper level low pressure
that had been impacting the forecast area has moved off into western
Montana. The main precipitation has shifted east of the forecast
area this morning so the winter weather advisories have been
expired. A secondary low has developed off the coast of Washington
so the forecast area will be between lows today. This will lead to a
few showers over the Wallowa county area and along the Cascades
otherwise dry and partly cloudy. Showers will end around sunset the
just partly cloudy overnight.


.AVIATION...18Z TAFs...VFR conditions will continue for the next 24
hours. A few showers may develop over the mountains this afternoon
and early evening but should not impact any TAF sites. Ceilings are
expected to be few to scattered above 4000 feet this morning then
becoming scattered to broken at 5000 to 8000 feet this afternoon and
early evening. Cloud cover will decrease through the night becoming
mostly clear after 15Z though KRDM and KBDN should be scattered at
5000 to 10000 feet. Winds will be generally westerly at 5 to 15 kts
through this evening with gusts to 25 kts at KALW and KPDT. After
03Z, winds will drop to below 10 kts. Perry


.PREV DISCUSSION... /issued 430 AM PDT Sun Mar 18 2018/

SHORT TERM...Today through Tuesday...An upper level trough
continues to weaken as it tracks across southeast Oregon and
southern Idaho this morning. However, it is still pushing wrap
around moisture into northeast Oregon and extreme southeast
Washington this morning. There are numerous snow showers in the
mountains, from the northern Blue Mountains eastward, with rain in
the lower valleys in these locations. A Winter Weather Advisory
remains in effect until at least 8 AM for Wallowa County and the
northern Blue Mountains. Will let these advisories continue this
morning. The snow showers will gradually decrease by later this
morning as the upper trough pulls away from the forecast area today
to the east. There will be a brief drying trend for this afternoon
and tonight. Meanwhile the next Pacific weather system will move
down the coast as a closed upper low tonight into Monday. It is
forecast to remain off the coast through Monday resulting in less
wrap around precipitation. However, it will bring more rain and
mountain snow showers to the southern and eastern forecast area by
Tuesday as a moist southwest flow develops over the CWA on the east
side of this upper low...which by Tuesday will begin to move back
toward the Oregon coast. Can expect more rain and mountain snow
showers from central Oregon eastward and northeast across the Blue
Mountains eastward and southward...including central and north
central Oregon. Snow amounts from this system, at this time, look to
be too light for any winter weather highlights, but will need to
watch this over the next couple days for the possible need of a
Winter Weather Advisory in some of the same areas as the most recent
advisories. It has been windy this morning in the Oregon Blue
Mountain Foothills with Pendleton having sustained winds of 15 to 25
mph with higher gusts. Elsewhere, winds are not as strong, and
mostly light, but the strongest winds are located over the open
terrain of the Lower Columbia Basin...especially the higher
elevations such as the Horse Heaven Hills and the hills separating
the Yakima and Kittitas Valleys. Temperatures will be near normal
over the next few days. Normal high temperatures for Pendleton, as
an example, for mid March is in the mid 50s...which is very close to
the forecast high temperatures. 88

LONG TERM...Tuesday Night Through Saturday...A series of upper
level troughs will move through WA and OR during the extended time
period. An upper level low and associated trough will move across WA
and OR Tuesday night. This system will bring a chance of rain high
elevation snow to central Oregon and the eastern mountains then
across the whole area on Wednesday. Snow levels Tuesday night and
Wednesday will be 4000-5000 feet. Snow levels will rise to 5000-6000
feet Wednesday night due to broad southerly flow ahead of another
trough approaching the coast. Models are in good agreement that the
trough will remain offshore Wednesday night through Saturday. It
will send a series of disturbances through the area. That will keep
a chance of rain or snow over the area Wednesday night and Thursday.
This trough will move slowly across WA and OR Thursday and Friday
with rain and snow likely. Snow levels will start mainly above 5000
feet Wednesday night then decrease to 800-1500 feet Friday. Coonfield


PDT  54  33  52  34 /  10   0  10  10
ALW  55  34  53  34 /  10   0  10  10
PSC  60  30  57  35 /  10   0  10   0
YKM  58  30  56  29 /  10  10  10  10
HRI  58  32  56  36 /  10   0  10  10
ELN  58  29  53  28 /  10  10  10  10
RDM  49  24  49  28 /  10  10  20  10
LGD  46  29  47  30 /  10  10  20  20
GCD  45  30  48  31 /  10  10  20  10
DLS  58  33  57  33 /  10  10  10  10




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