Area Forecast Discussion
Issued by NWS Pendleton, OR

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711
FXUS66 KPDT 211745 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
945 AM PST Tue Feb 21 2017

Updated AVIATION Discussion

.UPDATE...Upper level trough moving through the area will keep
periods of precipitation likely through the day today. Snow levels
will be around 1500 feet in Washington, 3000-3500 feet over northern
Oregon and around 4000 feet in Central Oregon today. Some of the
showers could be moderate to even briefly heavy at times. Will need
to watch rainfall rates carefully, as some areas could experience
some urban and small stream issues if rain rates increase enough.
Snow amounts look to be light over the Kittitas Valley and WA East
Slopes today, likely under 1 inch. Snow amounts should stay just
below advisory criteria in the Blue Mtns, where 3 to 6 inches is
expected through tonight above 4000 feet. Winds will be breezy
across our Oregon zones through the afternoon hours, but mixing down
of winds aloft does not look nearly as efficient as yesterday.
Therefore expect some gusty winds along the ridge tops, especially
in the Southern Blue Mtns, Ochoco-John Day Highlands, Grande Ronde
Valley and into Wallowa County. In these areas, expect peak gusts of
30-45 MPH today, again just below advisory criteria. Further north,
across the Blue Mtn Foothills and Lower Columbia Basin, expect
westerly winds to increase later this afternoon with gusts up to 30
MPH. Showers gradually shift east and taper off this
evening/tonight. Lingering snow showers are likely in the northern
Blue Mtns overnight. 77

&&

.AVIATION....18Z TAFS...BKN-OVC today. Light rain showers will
producing VFR to MVFR conditions. Westerly winds will increase
becoming 10-20 kts with higher gusts by afternoon and into evening
before decreasing. Rain will tapper off afternoon and into the
evening leading to VFR conditions overnight.  Polan

&&

.PREVIOUS DISCUSSION... /issued 333 AM PST Tue Feb 21 2017/

SHORT TERM...Today through Thursday...A large upper level trough
remains off the Pacific Northwest coast this morning and is sending
a plume of moisture over the area along with colder air. A band of
precipitation is crossing Northeastern Oregon and Eastern Washington
with mainly rain with snow above 4000-4500 feet. Behind this band,
rain and mountain snow showers will continue through the afternoon.
The colder air will lower temperatures around 10 degrees from
yesterday with highs mainly in the 40s. Winds will not be as strong
as yesterday, but 15 to 30 mph winds are expected in Central Oregon,
the Ochoco-John Day Highlands and the Grande Ronde Valley. The
southern Grande Ronde Valley will approach Wind Advisory levels, but
it looks like they will stay just below it. Winds will decrease
rapidly in the early evening. Further north, winds will pick up to
10-20 mph in the afternoon. Precipitation amounts in the Flood Watch
area have been reduced for today and believe flooding is less
likely. May drop the watch in the next couple of hours after looking
in greater detail and coordinating with the Spokane office. Tonight
the trough will move closer to the coast. Precipitation will be
mainly in the mountains and will diminish through the night. The
lower elevations will have a chance of rain in the evening and the
mountains will have a chance of rain and snow in the evening with
snow levels around 3000 feet and then a chance of snow overnight as
snow levels drop to 1500-2000 feet. The Blue Mountains will get 1-3
inches of snow with other mountain locations getting less than 2
inches. Lows will be colder and generally in the upper teens and
20s. Wednesday the trough will move to the coastline and on
Wednesday night and Thursday it will move over the area. This will
keep a chance of mainly snow in the mountains while the lower
elevations will be mostly dry. Snow levels will be 500-1500 feet
Wednesday and Wednesday night and then on Thursday it will be around
500 feet. Precipitation amounts will be very light, so even in the
mountains an inch or less of snow is expected. Temperatures will
remain cool with highs in the 30s to around 40 and the lows
Wednesday night will be in the mid teens to mid 20s. Perry

LONG TERM...Friday through Tuesday...Forecast area will be under a
cooler northerly flow through Sunday then becoming northwest Monday
and Tuesday. A couple of shortwaves will drop south along the
Canadian coast Friday through Sunday that remain off the Pacific
Northwest coast before eventually swinging into California. These
system will not directly impact the forecast area as most of the
storm energy remains off the Pacific Northwest coast before moving
into California. However, there could see some snow showers in areas
favored by the northerly upslope flow. Monday and Tuesday the
northwest flow will keep some lingering showers mainly over the
mountains.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  42  30  42  25 /  90  50  20  10
ALW  45  33  40  24 /  90  60  20  10
PSC  44  30  40  26 /  80  20  10  10
YKM  42  27  40  21 /  70  10  10  10
HRI  44  30  39  24 /  80  20  10  10
ELN  38  26  36  17 /  60  10  10  10
RDM  43  23  38  18 /  50  40  30  20
LGD  44  30  40  23 /  70  50  30  20
GCD  47  26  39  23 /  80  60  30  20
DLS  44  33  37  29 /  80  10  20  10

&&

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

$$

77/99/83/



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