High Wind in Oregon, February 23, 2020

Area Forecast Discussion
National Weather Service Pendleton OR
946 AM PST Sun Feb 23 2020

Updated Aviation Discussion

SHORT TERM...An upper low centered over northern Vancouver Island
is sending a trough and cold front ashore this morning. The cold
front is moving into the Washington Cascades at this time and
webcams show heavy snow falling near Snoqualmie Pass. The front
will be a fast mover and the period of heavy snow in the mountains
and rain elsewhere will be around 4 to 6 hours. Cold air behind
the front will allow some lighter convective showers to develop
late this afternoon and evening. Models show some instability late
this afternoon around Dayton and in the Washington portion of the
Blue Mountains. Considered adding a slight chance of
thunderstorms there but ultimately decided the chance were too
low. The main impact will be winds this afternoon and evening.
Current forecast of widespread 25 to 35 mph winds with gusts to 50
mph looked good and the only changes were to lower winds a few
mph in the Grande Ronde Valley and the John Day Basin. Winds will
decrease overnight. Made a few temperature adjustments today and
precipitation and cloud cover adjustments today and tonight.
Forecast update already out. Perry

AVIATION...18Z TAFs...Cold front beginning to impact the region
this morning, and will continue to move east bringing light rain
to or near most TAF sites into the early afternoon. TAF sites will
see bkn-ovc ceilings lower to 040-070 with approach of frontal
boundary, but clearing to sct-bkn after passage of frontal
boundary. Winds will quickly increase as frontal boundary moves
over TAF sites, with winds becoming westerly at 20-40kts by late
morning through the afternoon, and slowly decreasing starting
later tonight. Lawhorn/82

PREV DISCUSSION... /issued 218 AM PST Sun Feb 23 2020/

SHORT TERM...Today through Tuesday night...A westerly zonal flow
continues with a low pressure system off the coast set to move into
southern british Columbia and the Pacific Northwest today. The front
associated with this system will sweep across the forecast area
midday and exit into Idaho in the afternoon. There will be some
precipitation associated with the frontal passage followed by very
windy conditions post frontal. Wind advisories have been issued for
the possibility of sustained winds of 30 to 40 mph and wind gusts
over 50 mph this afternoon and evening before winds begin to
decrease overnight. Most of the precipitation will be short-lived
but behind the front there will be some showers along the Cascade
crest and over the eastern mountains with lowering snow levels down
to around 1500 feet tonight. Accumulations look to be below advisory
levels except maybe along the Cascade crest region. A ridge of high
pressure will quickly build off the coast which will move inland
late Monday. This will bring an end to the showers and back to a dry
and light wind pattern Monday night and Tuesday.

LONG TERM...Wednesday through Sunday...On Wednesday, a weak
shortwave over topping the ridge may flatten it a bit and allow for
increased mid/high level moisture and clouds and possibly a few
light mountain showers. Ridging then expected to quickly build back
and strengthen over the western CONUS. As we head towards the
weekend, models differ a bit, with biggest discrepancy being timing
of the next system, but the general trend is for the ridge to weaken
and shift east as mean troughing approaches the west coast Friday
night into early Saturday. Precip expected to then spread east over
the region Saturday afternoon/evening with the initial frontal
passage. Mountain snow and low elevation rain showers possible into
Sunday as the strengthening upper low/trough expected to drop south
and east over the western CONUS. Warming trend through the end of
the work week with highs in the mid 40s to mid 50s Wednesday,
climbing to the 50s to lower 60s Friday. Cooler temps for the
weekend with the system passing overhead. Patchy fog possible
Thu/Fri morning in the lower Columbia Basin.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  55  36  48  27 /  70  10  10   0
ALW  55  35  49  27 /  70  10  10   0
PSC  56  36  53  26 /  30   0   0   0
YKM  52  29  51  23 /  50  10   0   0
HRI  56  37  51  25 /  40   0   0   0
ELN  46  34  45  23 /  70  20   0   0
RDM  53  25  47  21 /  30  10   0   0
LGD  48  29  42  24 /  90  30  20   0
GCD  52  30  43  25 /  60  20  10   0
DLS  51  38  49  28 /  60  20  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 1 AM PST Monday for ORZ041-044-507-508-510-
     511.

WA...Wind Advisory until 1 AM PST Monday for WAZ024-026>029-521.

     Winter Weather Advisory until 4 AM PST Monday for WAZ520.

&&

83/82/82