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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

                            
000
FXUS66 KPDT 200534 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
933 PM PST Tue Feb 19 2019

Updated Aviation Discussion

.SHORT TERM...Water vapor imagery showing upper low quickly moving
into the Pacific northwest this evening being pushed along by a
strong jet. Would expect cold advection from this point forward 
so any mixed precipitation in the Columbia basin should turn over 
to all snow overnight. West northwest flow aloft is hitting the 
Cascades and Blues fairly hard with moderate snow reported for the
past several hours at Stampede and Meacham. This will likely 
continue overnight with significant accumulations. The remainder 
of the forecast area will have light snow at times. The low moves 
across the region late tonight and Wednesday. Expect snow will 
continue through the period. Temperatures should be a little 
colder tomorrow with mid 20s to mid 30s. By Wed night the low is 
moving into Nevada and precipitation should be decreasing from 
north to south across the forecast area. Weak upper ridge and dry 
northerly flow Thursday with partly to mostly cloudy skies. 94

&&

.AVIATION...06Z Tafs...Bands of light snow are spreading across 
the area tonight with lowering CIGS and VSBYS. Best potential for 
IFR will be at KALW...KPDT... KRDM...and KBDN though all sites 
should see at least MVFR conditions tonight through Wednesday. 
Heaviest snow tonight will likely be at KPDT. Winds will be 
generally light. 76


.PREV DISCUSSION... /issued 245 PM PST Tue Feb 19 2019/ 

SHORT TERM...Tonight through Thursday...A strong system is moving 
into the area this afternoon and will bring significant snow to 
portions of the area tonight and tomorrow before winding down 
Wednesday night. Radar already has returns filling in over the 
Columbia Basin and Blue Mountains. Webcams are showing rain near 
Snoqualmie Pass and snow in the Blue Mountains. Precipitation will 
intensify and increase tonight and current Winter Weather Warnings 
and Advisories will remain in effect though models have trended 
somewhat warmer and this may lead to rain mixed with the snow at 
times in the Blue Mountain Foothills. The Yakima and Kittitas 
Valleys and Columbia Basin will be shadowed and snow amounts will be 
limited to an inch or two. A couple of the models also give a slight 
indication of enough warming aloft and colder air at the surface 
tonight in the Columbia Basin and Blue Mountain Foothills so have 
kept a mention of freezing rain and sleet there but have cut it back 
to a slight chance. By late Wednesday night and Thursday morning 
snow will have ended in the Columbia Basin and have lowered to a 
chance of snow in Central Oregon and the eastern mountains. Thursday 
afternoon will be dry aside from some lingering light snow showers 
over the highest mountains of northeast Oregon. Highs tomorrow will 
be in the upper 20s and lower 30s except for some mid 30s from the 
Columbia Gorge south into central Oregon. Thursday will be a couple 
of degrees cooler. Lows tonight will be generally in the 20s with a 
few places around 30 in the Columbia Basin. Wednesday night will be 
in the mid teens to mid 20s. Perry

LONG TERM...Thursday night through Tuesday. There will be another 
brief break from the snow on Thursday night and Friday ahead of the 
next system to start moving in Friday night.  A large trough of low 
pressure will sink south over the area with several pieces of energy 
to rotate through the trough during the weekend and into early next 
week. Models start to diverge late in the extended with the GFS 
still on the cold side and bringing a band of moisture north over 
Oregon on Tuesday while the EC keeps a closed low further north and 
much warmer air to spread over Oregon. The GFS solution has been 
more consistent so have blended but leaned more towards it. 
Temperatures moderate a bit through the weekend, but remain well 
below normal. 93 


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  28  32  21  29 /  90  90  30  20 
ALW  28  32  22  30 / 100  90  30  20 
PSC  25  33  21  34 /  50  60  10  10 
YKM  23  35  21  36 /  40  40  20  10 
HRI  29  34  22  34 /  60  70  20  10 
ELN  20  34  18  36 /  50  40  20  10 
RDM  25  35  19  32 /  70  80  50  10 
LGD  26  33  21  31 /  90  90  40  20 
GCD  27  34  18  30 /  90  90  40  20 
DLS  31  38  25  39 /  70  60  30  10 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 PM PST Wednesday for ORZ505-506-
     509.

     Winter Storm Warning until 4 AM PST Thursday for ORZ050.

     Winter Storm Warning until 10 PM PST Wednesday for ORZ502-507.

     Winter Weather Advisory until 10 PM PST Wednesday for ORZ049-503.

WA...Winter Storm Warning until 10 PM PST Wednesday for WAZ030.

     Winter Storm Warning until 4 PM PST Wednesday for WAZ029.

     Winter Weather Advisory until 1 PM PST Wednesday for WAZ520.

&&

$$

94