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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 180305

Area Forecast Discussion
National Weather Service Pendleton OR
705 PM PST Sun Feb 17 2019

.SHORT TERM...Short wave moving through in the northerly flow 
aloft combined with a cold front resulting in scattered snow 
showers and cloudy skies. Expect this will continue overnight.
Northerly flow continues Monday although the airmass is drying so
partly to mostly cloudy skies. The next system to impact the
region will be a low moving across the Pacific northwest Tuesday 
into Wednesday. This will result in another round of accumulating
snowfall. Model precipitation forecasts show a significant amount
for the mountains. Temperatures will remain well below normal 
through the period. 94


.PREV DISCUSSION... /issued 239 PM PST Sun Feb 17 2019/ 

SHORT TERM...Tonight through Wednesday...A large trough remains
over most of the CONUS this afternoon. An upper low is moving
south over northern California and Nevada and its influence over 
our area is steadily decreasing. Another low pressure area in 
southern Alberta is sending a cold northerly flow into the area. 
Moisture is limited with the incoming arctic air but radar is 
showing some returns over the Columbia Basin and Blue Mountain 
Foothills. Am expecting isolated light snow showers mainly over 
the Washington Cascades, Blue Mountain Foothills and northeast 
Oregon mountains but anywhere aside from the Washington Columbia 
basin and Central Oregon could see a stray shower. Snow amounts 
will be less than an inch. Snow showers will taper off tomorrow 
morning and the area will get a break Monday afternoon through 
Tuesday morning. The main story will be colder temperatures as 
lows tonight will be in the teens and in the mid single digits to 
mid teens Monday night. Tomorrow will have high temperatures 
mainly in the 20s though central Oregon should reach the lower 
30s. The next concern will be a system out of the Gulf of Alaska 
arriving Tuesday afternoon and impacting the area through 
Wednesday. The entire area will have snow with this system and 
winter weather highlights appear probable Tuesday night and 
Wednesday over the Blue Mountain Foothills, Grande Ronde Valley 
and Wallowa county (2-5 inches) and eastern Oregon mountains (4-9 
inches). The rest of the area will get 1-3 inches. Future shifts 
will have to monitor to see when the confidence is there for any 
watches, advisories and warnings to be issued. With increased 
cloud cover, lows Tuesday night will be in the 20s and highs 
Wednesday will be in the mid 20s to mid 30s. Perry

LONG TERM...Wednesday night through Sunday. Snow showers will 
linger over the area Wednesday night as the upper level system 
starts to move east.  It will continue to be cold through the week, 
but should be drier Thursday into Friday as a ridge of high pressure 
moves through.  Another low pressure system will be approaching the 
area Friday night with a chance of light snow across the area 
Saturday with a cold front Saturday night.  The upper level trough 
remains over the area Sunday with another low dropping down the 
coast.  This will turn the flow more zonal and keep some area just 
east of the Cascades more shadowed from light snow but most area 
will continue to see some periods of light snow. Temperatures will 
remain below normal. 93 

AVIATION...00z TAFs. IFR/LIFR low clouds and fog will continue 
through the evening at PDT/ALW/PSC as band of low clouds continue 
to move south over the area and bank up against the Blue 
Mountains. YKM will also see slight upslope flow with light snow 
and MVFR conditions overnight. Northerly flow will continue on 
Monday with some clouds banked along the foothills with MVFR at 
ALW/PDT and mainly VFR at other locations. 93 


PDT  18  29  13  30 /  30  10   0  20 
ALW  19  28  15  30 /  30  10   0  20 
PSC  19  30  15  29 /  20   0   0  20 
YKM  22  31  15  30 /  30  10   0  20 
HRI  21  31  16  31 /  20  10   0  20 
ELN  18  30  13  30 /  30  10  10  30 
RDM  18  34  16  36 /  10  10  10  20 
LGD  16  28  11  31 /  30  10   0  30 
GCD  19  29  14  33 /  10  10  10  20 
DLS  26  37  24  37 /  20  10  10  30