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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 232220

Area Forecast Discussion
National Weather Service Pendleton OR
220 PM PST Sat Feb 23 2019

.SHORT TERM...Tonight through Tuesday...An upper level trough is 
exiting out of western Canada and into the Gulf of Alaska. This 
trough will settle a little further southward and then stall over the 
coming days. This will allow the trough to begin tapping into some 
moisture over the eastern Pacific and spread it into the region 
starting tonight and continue through the first of the week. The 
main focus for precipitation will be over Oregon where the moisture 
plume seems to be aimed. The plume will briefly lift north a couple 
of times over the coming days so even southern Washington will see 
an impact at times but not on the same level as Oregon. This will 
mainly be a snow event but central Oregon will see a mix of rain and 
snow at times as snow levels fluctuate. Some significant snowfall 
accumulations are expected through Tuesday with numerous winter 
storm warnings and advisories in effect for all zones covered by 
this office. Travel may become difficult and dangerous across 
portions of eastern Oregon through the first of the week. 

.LONG TERM...Tuesday night through Saturday...The persistent upper 
level trough offshore that shuttled substantial amounts of moisture 
into the region resulting in a significant winter storm is expected 
to deepen into a closed low and drift east before getting caught up 
in stronger flow heading south out of the Canadian prairies and 
ejecting east Wednesday afternoon. This should result in a break in 
precipitation late Thursday into at least Friday. The next plume of 
moisture arrives for the weekend, but at this point looks like it 
may stay confined to northern California/southern Oregon. The 
biggest thing to watch with this system would be any poleward 
trending - with a substantial snow pack in place surface 
temperatures would likely struggle to get above freezing quickly 
despite strong warm air advection aloft resulting in freezing rain. 


.AVIATION...00Z TAFs...Deteriorating conditions in snow are expected 
overnight with the approach of a significant plume of mid-level 
moisture. Heavy snow begins first at DLS with RDM/BDN/PDT joining in 
through early morning. Through Sunday afternoon the heaviest 
accumulations will be at DLS/PDT. BDN/RDM may initially see some 
precipitation shadowing but will fill in during the morning with 
heavy snow. Light snow is expected at PSC/YKM/ALW with the heavier 
band staying south of those terminals.


PDT  27  29  24  29 /  60  80  50  80 
ALW  26  31  26  29 /  20  70  30  70 
PSC  26  31  24  29 /  20  60  20  60 
YKM  25  30  22  29 /  60  70  20  60 
HRI  28  31  25  30 /  60  80  40  70 
ELN  23  31  19  29 /  50  60  20  50 
RDM  31  35  25  30 / 100  90 100 100 
LGD  28  34  25  33 /  80  90  70  90 
GCD  31  37  31  40 / 100 100  90  90 
DLS  31  33  28  31 /  90  90  80  90 


OR...Winter Storm Warning until 4 AM PST Wednesday for ORZ503-505-506-

     Winter Storm Warning from 10 PM this evening to 4 AM PST 
     Wednesday for ORZ041-044-049-050-507.

     Winter Storm Warning until 4 AM PST Wednesday for ORZ502.

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

     Winter Storm Warning until 4 AM PST Wednesday for WAZ030.

     Winter Weather Advisory from 10 PM this evening to 4 AM PST 
     Wednesday for WAZ026>029.