Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 220306

Area Forecast Discussion
National Weather Service Pendleton OR
806 PM PDT Thu Sep 21 2017

.SHORT TERM...Tonight and Friday...A large elongated upper level
trough over the region will close off overnight becoming a closed
upper level low over southwest Idaho by Friday morning. The
afternoon instability showers are decreasing and will end across
most of the forecast area this evening. However, there could be some
lingering showers over the Wallowa and Elkhorn mountain areas as
some moisture begins to wrap around the closed low and comes back
into the area from Idaho. Friday will be similar to today with some
developing instability showers in the afternoon mainly over the
mountainous terrain. Temperatures will continue to be cool but up
slightly over Thursday`s highs.


.PREV DISCUSSION... /issued 223 PM PDT Thu Sep 21 2017/

SHORT TERM...Tonight through Sunday...A large elongated upper level
trough stretching from Hudson Bay to central California remains
draped across the area though it is slowly moving eastward as an
offshore ridge tries to build into our area. A cold northeasterly
flow is bringing in a limited amount of moisture but convective
clouds are developing and a few rain showers with snow above 5500
feet have formed in the northern half of the area. Expect that
upslope flow will develop a few showers in central Oregon and the
eastern mountains this evening, so have a slight chance of showers
across the area except for the Columbia Basin which should remain
dry. Precipitation amounts will be on the order of a few hundredths
of an inch. Do not expect thunderstorms due to the limited
instability. It should be another cold night with temperatures a
couple of degrees cooler than last night. Lows should be in the
upper 30s and 40s with mid 20s to mid 30s in the mountains. By
tomorrow morning, the trough will have moved into Idaho and it will
be splitting with a closed low forming near the Idaho/Nevada border
and the rest of the trough reforming in northern Alberta. The closed
low will keep sending a northeast wrap around flow into our area so
am expecting a slight chance of rain and snow showers in the
mountains with snow levels around 6000 feet. Once again, rain and
snow amounts will be quite light, Highs will rise about 3-5 degrees
with upper 50s to mid 60s in the lower elevations and upper 40s to
mid 50s in the mountains. By Friday night, showers will be confined
to the higher terrain of the the eastern Oregon mountains and
Wallowa county. By Saturday, the low will have drifted southeast and
be centered near the Nevada/Utah border. The offshore ridge will
have expanded into our area and the flow will be shifting to the
north. The situation will remain fairly stagnant through Sunday with
the low shifting a couple of hundred miles east to central Utah and
our flow will turn northwest by Sunday afternoon. It should be dry
Saturday through Sunday with temperatures warming to the upper 60s
to mid 70s with mid 50s to mid 60s in the mountains. Perry

LONG TERM...Sunday night through Thursday...Mainly dry conditions
and a warming trend are expected through the extended period.  Cool
northerly flow will continue Sunday night and into Monday with some
limited moisture for the Washington Cascades and northern Blue
Mountains.  Heights start to increase on Tuesday as the ridge is
expected to be along the coast and then slowly progress inland
through Thursday.  Temperatures will start the week near normal and
then warm to about 5 to 7 degrees above normal by Thursday with
highs in the upper 70s to near 80 and upper 60s to lower 70s in the
mountains. 93

AVIATION...00z TAFS...VFR conditions are expected for the next 24
hours.  Sct-bkn cigs 050-070kft and a few isolated showers will be
dissipating after sunset. Upper low will drift slowly southeast out
of Oregon late tonight and Friday with a few showers over the
northeast mountains and sct clouds 050-070kft through the day. 93


PDT  44  63  43  68 /  20  10  10  10
ALW  44  66  48  71 /  20  10  10  10
PSC  41  69  46  73 /  20   0  10  10
YKM  40  67  46  71 /  20  10  10  10
HRI  43  67  44  71 /  20  10  10  10
ELN  43  67  45  71 /  20  10  10  10
RDM  32  59  35  67 /  20  10  10  10
LGD  39  56  35  62 /  20  20  10  10
GCD  38  56  35  64 /  20  20  10  10
DLS  48  71  49  74 /  20  10  10  10




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