Winter Storm and Heavy Snow in Washington, February 22 to 26, 2019

Area Forecast Discussion
National Weather Service Pendleton OR
910 PM PST Fri Feb 22 2019

.UPDATE...The latest radar was showing a band of precipitation
over the blue mountains and its foothills. In the blue mountains
light snow was accumulating and this will continue tonight and a
winter storm warning remains in effect in this area for the next
several days. Elsewhere and along the foothills of the blue
mountains rain may mix with the snow at times. The snow will
expand into the grande ronde valley and the wallowa region
overnight. The greatest chances of pcpn will occur in the
mountains that also includes the wa/or cascades. The bulk of the
pcpn drifts south and into the ochoco mountains and john day
valley later tonight. Although there may be a brief break in the
pcpn tomorrow...light snow will persist and increase in intensity
and coverage Saturday afternoon and night when additional winter
weather warnings go into effect. Some changes were done to wx and
pops along with sky and qpf tonight and temps are expected to fall
into the 20s with teens in the mountains.

&&

.PREV DISCUSSION... /issued 213 PM PST Fri Feb 22 2019/

SHORT TERM...Tonight through Monday...Initial wave of
precipitation associated with approaching cold front has arrived
in the Cascades this afternoon. Through midnight tonight
accumulations above 1 inch will be limited to the immediate
Cascade crest and eastern mountains where 4 to 10 inches will be
possible, with the highest amounts in the northern Blues between
Tollgate and Ski Bluewood. Precipitation shadowing will limit any
accumulation potential in the Columbia Basin to a trace. The cold
front will continue to sag south overnight and into Saturday
morning and will be the major focus for significant snowfall
Sunday into early next week as it drifts back to the north.
Moisture streaming over this boundary will create conditions
favorable for near continuous, relatively light snow with an
increase in intensity expected during the day Sunday and again
early Monday morning as a more substantial plume of moisture
arrives. This heavier precipitation will primarily impact the
Cascades, north central/central Oregon, the Columbia River Gorge
and Simcoe highlands. Models have converged enough on this
solution to issue long duration Winter Storm Warnings for the
Cascades, central/north central Oregon, the Columbia River Gorge,
Simcoe Highlands, Blue Mountains and Wallowa County valid through
early Wednesday morning. While surface temperatures may be
marginal for accumulating snow especially during the afternoons we
are expecting storm total snow amounts in these areas of 10 to 20
inches. The warning for the northern Blues will go into effect
tonight where low end warning amounts with the aforementioned
front will occur in additional to the long duration snow Saturday
night through Wednesday morning. Will leave current watches in
effect or issue new watches for the remainder of the area where
confidence in significant travel impacts with a long duration snow
event are lower. Peck

LONG TERM...Monday night through Friday...Active weather pattern
will persist through mid week as a frontal boundary meanders north
and south across the forecast area. Used an ensemble approach for
much of the forecast due to the uncertainty and spread exhibited in
the deterministic models. Monday night and Tuesday a warm front will
be lifting north across Oregon into southern Washington with
moderate to locally heavy snow along and north of the boundary.
Accumulations could be significant especially in the mountains.
Lower elevation accumulations could be tempered a bit by marginal
temperatures...but could still accumulate in the colder areas and
under the heavier snow bands. Wednesday the front will begin to sag
sewd as a cold front with the heaviest snow over the eastern
mountains. By Thursday most of the precipitation will have ended.
Friday looks mostly dry and cold with much below normal
temperatures. 78

AVIATION...00Z TAFS...VFR conditions will prevail through the
forecast period. Ceilings will lower to 4-5K feet AGL by this
evening as a cold front moves across the region. A few light snow
showers will also be possible with brief MVFR conditions. Winds have
picked up a bit from the SW ahead of the front this afternoon at 10-
15 kt but will decrease to AOB 10 kt tonight. Expect mostly dry
conditions on Saturday with sct-bkn stratocumulus and mid cloud
above. A few mixed rain and snow showers could affect KBDN and KRDM
late in the day. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  27  35  25  31 /  50  10  60  80
ALW  28  36  25  33 /  80  20  30  50
PSC  23  34  25  32 /  20   0  30  40
YKM  17  33  23  32 /  10  20  40  50
HRI  28  37  26  33 /  20  10  40  70
ELN  18  32  19  31 /  20  30  50  40
RDM  27  40  30  40 /  30  40  70  70
LGD  25  35  26  37 /  80  60  70  80
GCD  27  36  30  39 /  70  60  80  90
DLS  29  40  30  35 /  50  30  70  80

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning from 4 PM Saturday to 4 AM PST Wednesday
     for ORZ503-508>511.

     Winter Storm Watch from Saturday afternoon through late Tuesday
     night for ORZ044-505>507.

     Winter Storm Warning from 10 PM Saturday to 4 AM PST Wednesday
     for ORZ041-050.

     Winter Storm Warning until 4 AM PST Wednesday for ORZ502.

     Winter Storm Watch from Saturday evening through late Tuesday
     night for ORZ049.

WA...Winter Storm Warning from 10 PM Saturday to 4 AM PST Wednesday
     for WAZ024-520-521.

     Winter Storm Warning until 4 AM PST Wednesday for WAZ030.

     Winter Storm Watch from Saturday evening through late Tuesday
     night for WAZ026>029.

&&

97/