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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

FXUS66 KPDT 260330 AAA

Area Forecast Discussion
National Weather Service Pendleton OR
830 PM PDT Thu Apr 25 2019

Added blowing dust wording

.UPDATE...The cirrus shield over the Pacific Northwest is growing
more dense this evening as a weak weather disturbance moves into 
the region over the top of a high pressure ridge. There is also 
increasing amounts of mid level clouds too. As this system moves 
across the region and forecast area tonight and early Friday, cannot 
rule out a sprinkle over the northeast mountains. However, the main 
effect will be increasing winds, mainly on Friday, and cooler 
temperatures. There will be some blowing dust over the Lower 
Columbia Basin and Blue Mountain Foothills Friday afternoon due to 
no rain expected in these areas. Another cold front with even cooler 
temperatures is expected Saturday night and Sunday. This will bring 
breezy to windy conditions again with cooler temperatures, 
especially at night. There will probably be some blowing dust again 
on Saturday in the same areas as Friday. Temperatures will drop into 
the 30s Saturday and Sunday nights. There could be a few light rain 
showers over the mountains, but this system looks fairly dry as 
well. 88


.AVIATION...06Z TAFs...VFR conditions are expected with mainly
just mid and high clouds tonight and Friday morning. Expect 
improvement with the clouds by Friday afternoon and evening. 
Breezy winds are expected for most areas Friday afternoon and 
evening with wind speeds of 15 to 25 kts...especially in open 
terrain and on the mountain ridge tops. 88


.PREV DISCUSSION... /issued 340 PM PDT Thu Apr 25 2019/ 

SHORT TERM...Tonight through Sunday...A low amplitude ridge of high 
pressure will remain over the region going into tonight but a fast 
moving shortwave is approaching from the west. This shortwave will 
pass over the area Friday morning followed by increasing westerly 
winds through the day. Will continue to see increasing high and mid 
level clouds ahead of the shortwave and then some clearing behind 
it. This system is lacking low level moisture so at best there might 
be a few showers over the Blue Mountains Friday but winds 15-30 mph 
will be the main impact and the potential for some blowing dust. 
Winds decrease a little Friday night but then increase again 
Saturday for another day of breezy conditions and potential blow 
dust. Following Fridays shortwave an upper level low in the Gulf of 
Alaska will settle into western Canada and place the forecast area 
under a cool northwest flow over the weekend. There will be some 
small weak impulses passing through the flow that will bring some 
occasional clouds and a low chance of precipitation mainly to the 
Washington Cascades and the northern Blue Mountain region. 
Temperatures will cool through the weekend and become below normal 
and even pose a threat for temperatures to drop to or below freezing 
by Sunday morning for areas around the Lower Columbia Basin.  

LONG TERM...Sunday night through Wednesday. Long term period begins 
with the PacNW under continued cool north to northwest flow with 
strong persistent ridging over the eastern Pacific. Another short-
wave low/trough will dig south down the east side of the ridge over 
the PacNW Monday into Tuesday. This will bring another reinforcing 
shot of cooler air and a chance of showers, mainly over the 
mountains. Snow levels will drop quite low for this time of year 
(3000-4000ft), but any accumulations are expected to be light. Gusty 
winds possible Monday and Tuesday ahead and behind the frontal 
passage. As the disturbance shifts east on Wednesday, a few 
lingering showers possible over the Blues/Wallowas. Another weak 
wave could fire off a few more light showers in the mountains on 
Thursday before a possible return of more wet weather late week. 
Temps look to continue the cooler trend next week with highs in the 
50s to mid 60s and lows in the 30s to low 40s.


PDT  45  66  41  59 /   0  10   0  10 
ALW  47  69  44  60 /   0  10   0  20 
PSC  48  72  46  65 /   0  10   0   0 
YKM  46  71  41  60 /   0   0   0   0 
HRI  47  71  44  63 /   0  10   0   0 
ELN  41  63  40  53 /   0   0  10  10 
RDM  39  65  35  61 /   0   0   0   0 
LGD  42  62  38  56 /   0  10   0  20 
GCD  42  63  37  60 /   0  10   0   0 
DLS  46  68  43  60 /   0   0   0   0