Area Forecast Discussion
Issued by NWS Pendleton, OR

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598
FXUS66 KPDT 161718 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
930 AM PST Tue Jan 16 2018

Updated Aviation Discussion

.UPDATE...A rather fast moving shortwave trough and associated
weak surface cold front is crossing eastern OR/WA this morning.
Widespread rain from the Columbia Basin eastward this morning will
taper off substantially by this afternoon, with some residual rain
and snow across far eastern OR into early afternoon. Have updated
the forecast for these trends. Low clouds this morning across the
lower elevations will scattered out in the wake of the front this
afternoon. Highs today will range from the upper 40s/lower 50s for
the lower elevations, with upper 30s/lower 40s for the mountains.

&&

.AVIATION...18Z TAFs...Showers will linger over the mountain
through this evening, with mainly VFR conditions at the TAFs sites
with sct-bkn clouds 030-050 kft.  Some fog and low clouds are
expected to push back in from the north tonight, mainly affecting
KYKM and KPSC with some patchy fog and possible MVFR with cigs.  A
warm front will be moving into the area on Wednesday morning with
some light rain possible at KDLS after 15z then pushing north
through the day. 93



&&

.PREV DISCUSSION... /issued 401 AM PST Tue Jan 16 2018/

SHORT TERM...Today through Thursday...The upper ridge that has been
over the region will weaken and move east today as a weather system
moves into the area. This system will bring some rain and higher
mountain snow to the forecast area today. It is a fairly fast moving
system, so the precipitation should be mostly done by this evening.
The moisture content is fairly high though and so all areas will
have at least chance to likely pops today. There is no need for any
winter weather highlights as snow levels are high and only the
highest mountains will receive snow. There will be a temporary break
tonight and early Wednesday morning before the next system moves
into the region by Wednesday afternoon. This system will bring
another round of precipitation to the area. Snow levels will be a
little lower with this next system and will need to keep alert for
possible winter weather highlights for the mountains. For now will
not issue anything due to uncertainty and it being too far into the
future. Conditions will remain unsettled as yet another weather
system moves in on Thursday with more rain and mountain snow. It
will be breezy to windy at times with each system, especially on the
ridge tops. Though winds are not expected to be strong enough for
any wind advisories. Temperatures will be and remain above normal
through most of the short term period. 88

LONG TERM...Thursday Night through Tuesday...Unsettled weather will
continue through much of the long term period. Thursday night and
Friday an upper trough will be located off the Pacific Northwest
coast. A front will be crossing the area thursday evening with a
chance of rain and mountain snow above 3500 feet before tapering off
to just a chance of snow in the mountains overnight. On Friday, the
upper low and trough will be weakening as it comes ashore. There
will once again be a chance of light rain showers in the lower
elevations with the Columbia Basin dry while the mountains will have
a chance of light snow showers. Weak ridging will try to build
Friday night as another upper low approaches the British
Columbia/Washington coast. There will continue to be a slight chance
of rain showers in the lower elevations and a chance of mountain
snow showers above 2500 feet. A weak disturbance will move through
the ridge Saturday and Saturday night and this will continue the
showery conditions with snow levels remaining around 2000-2500 feet.
Models are in good agreement in having the upper low move ashore
with a frontal system and slowly cross the area Sunday through
Monday night. Like the previous trough, it will weaken considerably
as it crosses the area. Sunday will have a chance of rain and
mountain snow but as the system and trough weakens, Sunday night
through Monday night will have a chance of lower elevation rain and
a continuing chance of mountain snow. Snow levels will remain around
2500 feet with this system. Models show a break Tuesday as ridge
moves over the area. The area will be dry aside from a slight chance
of some light mountain snow showers. Temperatures will be in the mid
30s to mid 40s Friday through Sunday then drop a couple of degrees
to mid 30s to lower 40s Monday and Tuesday. Perry

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  48  35  49  40 / 100  10  10  70
ALW  49  37  50  41 / 100  10  10  70
PSC  47  35  45  39 / 100  10  10  60
YKM  46  33  42  35 /  90  10  30  60
HRI  50  35  48  39 / 100  10  10  70
ELN  43  32  39  32 /  90  10  30  70
RDM  49  31  51  32 /  50  10  10  60
LGD  46  34  45  39 /  90  10  10  70
GCD  49  33  48  39 /  90  10  10  60
DLS  52  38  47  38 /  70  10  30  70

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

80/93/83



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