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FXUS66 KPDT 222152

Area Forecast Discussion
National Weather Service Pendleton OR
250 PM PDT Sun Apr 22 2018

.SHORT TERM...Tonight through Wednesday...A weak trough of low 
pressure is crossing interior WA/OR this afternoon. Little/no deep 
layer moisture is associated with the trough, with mostly sunny 
skies area wide. The trough will exit to the east tonight, and with 
any pooling of moisture well to the east, expect mainly clear skies 
tonight. With light winds, this will result in good radiational 
cooling. There is some disagreement in model solutions, with the 
blend of all models in the mid 30s for the lower elevations, while 
the MET/MAV/ECS numeric guidance is clustered around freezing. Given 
last nights readings leaning toward the cooler guidance, will blend 
the numeric guidance, with lower 30s for most lower elevation 
locations. An hour or two of freezing temperatures will be possible 
but with scattered coverage of freezing temperatures, will not issue 
a freeze warning. Ridging will build across the area Monday, 
hovering over the region and amplifying Tuesday and Wednesday. Clear 
skies will prevail, with a significant warmup. Expect slightly above 
normal highs Monday, rising through the 70s Tuesday, with the 
warmest temperatures this spring thus far Wednesday with lower 80s 
for the lowest elevations.

.LONG TERM...Wednesday night through Sunday night...Mid-upper
level ridge of high pressure will still be over the forecast area
Wednesday night. Thursday the ridge axis moves into Idaho thus
allowing flow aloft east of the Cascades to back to the south,
which opens the door for a large mid-upper level low pressure system 
near 132W roughly west of northern California to ease its eastern 
flank southerly flow aloft into central Oregon for, but deep layer 
moisture will be a tad to dry to support moist convection in central 
Oregon through Thursday afternoon. Compromise between the 12Z GFS 
and ECMWF runs for Thursday going forward. The ECMWF has shown the 
best day-to-day run consistency so forecast is based on that model.
Thursday night the low introduces a moisture plume into the region 
for increasing chances of showers through Sunday night. Slight 
chance of thunderstorms Friday and Friday night in eastern Oregon. 


.AVIATION...18Z TAFs...VFR conditions for the next 24 hours. 
Variable high clouds 30K feet AGL decreasing this afternoon.
Light upslope winds during daylight hours transitioning to
downslope drainage winds this evening.  Polan


PDT  35  67  37  75 /   0   0   0   0 
ALW  37  70  40  77 /   0   0   0   0 
PSC  32  72  35  77 /   0   0   0   0 
YKM  33  71  36  75 /   0   0   0   0 
HRI  32  70  33  77 /   0   0   0   0 
ELN  32  67  37  71 /   0   0   0   0 
RDM  23  68  28  76 /   0   0   0   0 
LGD  31  64  35  70 /   0   0   0   0 
GCD  34  66  38  72 /   0   0   0   0 
DLS  36  73  37  78 /   0   0   0   0 



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