Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 251745 AAA

Area Forecast Discussion...Update
National Weather Service Pendleton OR
1045 AM PDT Sat Mar 25 2017

Updated Aviation Discussion

.SHORT TERM...Today through Sunday...A cold front exited the region
overnight leaving a weak upper level trough to pass over the area
today. As it does there will be enough instability to generate some
showers mainly near or over the mountainous areas. The trough will
exit to the east tonight bringing an end to the showers this
evening. The next weather system will begin to move into the region
on Sunday as a warm front spreading precipitation across the
forecast area during the day. Snow levels will range from 3000 feet
over central Washington to 5000 feet over Oregon. This means there
will be some snow in the higher elevations on Sunday but no
significant accumulations.

.AVIATION...18z TAFS...VFR conditions are forecast to continue
through much of the next 24 hours. Expect SCT to BKN skies this
afternoon with some cumulus build up under marginally unstable
conditions. Cloud bases will range from 5k to 8K feet for most
locations. A rain shower or two could also affect KPDT and KALW
through the mid afternoon hours. Skies will clear for a time this
evening before additional high clouds move in overnight. The high
clouds will lower and thicken toward daybreak Sunday. Light rain
will be possible over the western TAF sites (KBDN, KRDM and KDLS)
prior to 26/18z. Expect low end VFR or Tempo MVFR cigs/vis in the
steadier rain by late Sunday morning over the western portion of the
area...spreading eastward by Sunday afternoon.

Westerly winds will range from about 8 to 15 kts over the area this
afternoon...with decreasing diurnal winds overnight and into Sunday
morning...mainly AOB 10 kts. 77


.PREV DISCUSSION... /issued 300 AM PDT Sat Mar 25 2017/

SHORT TERM...Today through Monday...A cold front has left the area
and is in Idaho this morning. Behind it, a trough is moving into the
area and will be crossing the area today. There will be enough
moisture and instability for scattered rain and snow showers in the
mountains with snow levels around 4000 feet. Most of the lower
elevations will have isolated rain showers though the Columbia Basin
should remain dry. Rain and snow amounts will be fairly light with
less than a tenth of an inch of rain and up to an inch of snow in
the mountains. The Columbia Basin should have winds of 10 to 20 mph
this afternoon though winds will be lighter elsewhere. Tonight the
trough will move into Idaho and weak ridging with a westerly flow
aloft will lead to a fair and dry night with partly cloudy skies.
The next weather system will move into the area Sunday morning with
likely rain and mountain snow above 5000 feet mainly in the
afternoon and Sunday night. Rain amounts look to be up to a quarter
inch in the lower elevations and up to an inch in the mountains.
Above 5000 feet, the mountains could get 3-5 inches of snow. Sunday
afternoon will see 10 to 20 mph winds in Central Oregon and the
Grande Ronde Valley. Behind this front another trough will move into
the area and keep another chance of rain and mountain snow above
4000 feet. As with today, rain and snow amounts will be fairly light
on Monday. Temperatures today and on Monday will be in the mid to
upper 50s in the Columbia Basin with mid 40s to mid 50s elsewhere.
Sunday will be in the mid 40s to mid 50s. Perry

LONG TERM...Monday night through Sunday...The extended period
continues to look unsettled in a progressive flow aloft. The CWA
will be in between weather systems at the start on Monday night and
Tuesday, but then another weather system will move into the region
on Wednesday. The GFS is the outlier model and keeps it mostly dry,
while the Canadian and other long range models show a wet weather
system to move through by midweek. Have therefore made just a few
changes to previous forecast of chance to likely pops. The unsettled
pattern then persists through the end of the extended period. There
may be a stray thunderstorm in the afternoons, but decided to not
mention it in the extended due to uncertainty and that it is too far
into the future. Temperatures will be near normal and winds will be
breezy at times...especially in central Oregon and north central
Oregon and on the ridge tops elsewhere. 88


PDT  53  37  51  39 /  20  10  50  70
ALW  55  41  53  42 /  20  10  50  70
PSC  58  37  54  42 /  20   0  50  70
YKM  60  35  53  38 /  10   0  60  70
HRI  56  37  53  40 /  20   0  50  70
ELN  52  31  47  33 /  10  10  70  70
RDM  53  32  54  32 /  20  10  60  70
LGD  53  34  52  38 /  50  20  40  70
GCD  54  35  53  37 /  30  10  50  80
DLS  56  39  53  40 /  20  10  70  70




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