Weather Service Report


327 
FXUS66 KPDT 231746
AFDPDT

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

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Western Regional Climate Center, wrcc@dri.edu