Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 270523
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
923 PM PST Sun Feb 26 2017

Updated aviation discussion

.SHORT TERM...Tonight and Monday...The upper level low along the
Oregon coast continues to slowly move inland and will be over
central Oregon by morning. It will then exit into Idaho by afternoon
followed by a weak shortwave arriving in the northwest flow. There
will be a decrease in showers overnight through early Monday but
then expect showers to increase in the afternoon as the next
shortwave arrives and we get a little surface heating which will
destabilize the atmosphere. Being showers in nature, snow
accumulations will be spotty overnight and Monday but a northwest
flow will favor the eastern mountains and especially the western
face of the Blue Mountains.

.AVIATION...06Z TAFs. Decreasing showers overnight the
increasing again Monday afternoon. CIGS and VSBYS will
vary due to the showers from VFR/MVFR to brief IFR in passing
showers. Winds will generally be less than 10 knots.

&&

.PREV DISCUSSION... /issued 330 PM PST Sun Feb 26 2017/

SHORT TERM...tonight through Tuesday night. Upper low centered
right along the Oregon coast this afternoon. Mixed rain and snow
at the lower elevations with temperatures in the upper 30s. Snow
at the mid and higher elevations with temperatures in the 20s to
lower 30s. Expect this will continue through the afternoon and
into the evening. Temperatures will fall after sunset and the low
will move inland across the forecast area tonight. Expect
precipitation to change over to all snow even at the lower
elevations. All models indicate the potential for a band of
heavier snow to develop and move across the region overnight just
to the north of the low center. This would likely be over central
or northern Oregon. Overnight lows will be in the 20s. The upper
low moves off to the east Monday however the region remains in a
cold northwest flow associated with a larger upper trough over the
Pacific northwest. A short wave will be moving through during the
afternoon into the evening and should enhance the precipitation
for a while. Similar to today expect lower elevation snow and rain
mixed with temps in the mid to upper 30s. Higher elevations will
remain all snow. Accumulations will continue in the mountains and
snow advisories will remain in effect through Monday night. For
Tuesday the northwest flow aloft continues however precipitation
will be much lighter and confined mostly to the mountains with
upslope flow. Temperatures will be a few degrees warmer with 30s
to mid 40s likely. 94

LONG TERM...Wednesday through Sunday. Washington and Oregon will be
under a northwest flow aloft Wed-Thurs night.  The winds will back
to the west Fri-Sat...then southwest Sat night.  Any precipitation
Wed-Thurs night will be along the Cascades...mainly WA...the
northern Blue Mtns and the Wallowas. The rest of the region will be
dry. When the flow backs to the west Friday...moisture off the
Pacific will spread across WA/OR and bring a chance of showers to
additional areas. However...there will be definite rain shadowing off
the Cascades and the Blue Mtns so that the Lower Columbia Basin and
surrounding valleys down to the Columbia Deschutes Plateau as well
as the Grande Ronde Valley, Wallowa Valley, and Imnaha Valley will
have little to no chance of precipitation.  The biggest concern Fri-
Sat will be strong winds.  The latest GFS and ECMWF are not as
impressive with the winds as previous runs...but it will be WINDY in
many areas...especially Friday afternoon and evening.  A westerly
jet streak juxtaposed over a tight SW-NE surface gradient will
result in strong winds in some areas. The westerly flow will buckle
in response to a developing trough offshore...and the flow will back
to the southwest Sat night and early Sun.  The upper level trough
and a strong cold front sweeping east of the Cascades early Sunday
will lower snow levels...possibly down to 1500 feet...and bring
scattered to numerous snow and rain showers along with breezy winds.
 Wister



&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  28  38  26  40 /  70  60  70  30
ALW  29  39  27  40 /  60  60  70  30
PSC  27  42  26  43 /  40  40  30  10
YKM  23  38  22  41 /  50  30  30  10
HRI  27  41  28  43 /  60  40  40  20
ELN  19  35  18  36 /  50  30  30  10
RDM  22  41  22  41 /  50  40  40  30
LGD  26  37  24  36 /  70  60  60  40
GCD  23  36  21  36 /  60  50  60  40
DLS  28  43  29  43 /  40  40  40  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST Tuesday for ORZ049-050-
     502-503-505-506.

     Winter Weather Advisory until 10 PM PST Monday for ORZ509.

WA...Winter Weather Advisory until 4 AM PST Tuesday for WAZ030.

     Winter Weather Advisory until 10 PM PST Monday for WAZ520.

&&

$$

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