Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 190443
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
843 PM PST Sat Nov 18 2017

.UPDATE...High pressure dominates the areas weather with dry
conditions tonight. Other than some mid and high level clouds the
dry conditions are expected to persist into tomorrow morning
before a storm system nears the area Sunday night. The winds are
generally light across the region with some gusts in the grande
ronde valley. Otherwise minor changes were done to the overnight
temps as they fall below freezing across most of the area and the
present forecast appears on track.

&&

.AVIATION...vfr conditions will persist at all taf sites for the
next 24 hours.

&&

.PREV DISCUSSION... /issued 240 PM PST Sat Nov 18 2017/

SHORT TERM...Tonight through Monday night...A low amplitude upper
ridge will persist over the region tonight. This ridge will
gradually flatten Sunday due to the approach of a weak disturbance.
As such will see fair and dry conditions with varying amounts of mid
and high level cloudiness tonight into Sunday morning. Some light
precip will begin to work into south-central Washington Sunday
afternoon. Snow levels at this time, in this area, look to be
between 3200 and 3900 feet. There may be some patchy fog along the
Interstate 90 corridor in Kittitas county late tonight into Sunday
morning. This disturbance will weaken as it moves across the region
Sunday night and Monday morning. A weak frontal boundary will get
pushed into the region by this disturbance, but it should stall out
across the Oregon Monday. Thus will see decent chances of precip due
to this slow moving front. Heaviest precip will be along the Cascade
east slopes where an onshore flow will cause additional precip due
to slop over from the west side of the Cascades. Snow levels will
rise Monday and Monday night over most areas, though they will
linger between 4000 and 4500 feet over Kittitas and Yakima counties.
Thus snow accumulations below 5000 feet should be limited. Winds
will be breezy to locally windy at times tonight through Monday,
especially over portions of the Grande Ronde valley, the Blue
mountains and their adjacent foothills, and central Oregon. 90

LONG TERM...Tuesday through Saturday...Models are in fairly good
agreement during the extended forecast period. There will be a broad
upper level ridge over WA and OR with a moist flow as multiple
systems move through the ridge. A warm front will move north Tuesday
and Tuesday night with widespread rain. Snow levels will be 6500-
9000 feet Tuesday...then increasing to over 8000 feet Tuesday night
through Thursday morning. More disturbances will keep varying
chances of rain Wednesday through Thursday morning. A cold front
will move through Thursday afternoon or evening. Precipitation will
decrease early Friday behind the front. Snow levels will come back
down to around 4000-6000 feet Friday. Friday night and Saturday the
models diverge from each other more significantly but the general
consensus is that a broad ridge with disturbances moving through it
will persist. Coonfield

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  30  55  42  54 /   0   0  70  60
ALW  35  58  46  56 /   0   0  80  70
PSC  30  54  42  56 /   0   0  60  30
YKM  27  49  35  53 /   0  10  50  30
HRI  27  53  42  55 /   0   0  50  40
ELN  26  46  34  49 /   0  10  60  20
RDM  23  54  38  55 /   0   0  50  70
LGD  31  50  39  50 /   0   0  80  80
GCD  26  52  40  50 /   0   0  50  60
DLS  31  52  42  53 /   0  10  70  60

&&

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

$$

97/97



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