Area forecast discussion...updated 
National Weather Service Pendleton or 
225 am PDT Wednesday Aug 20 2014 

Updated aviation discussion 

Short through upper trough over the region 
will persist through the extended forecast period. The trough axis 
will move eastward slightly causing a northwest flow on the back 
side of the trough for today through Thursday morning over the County Warning Area. 
This will keep dry and stable conditions over the County Warning Area through that 
time period. Maximum temperatures will be on a cooling trend with highs 
only in the middle 70s to lower 80s...except 60s to lower 70s 
mountains. Overnight lows will range from the middle 30s to middle 40s 
mountains to the 50s in the lower elevations. An upper low pressure 
system will develop over the Pacific northwest and slide south into 
the County Warning Area on Friday. This will transport more unstable air into the 
County Warning Area on Friday. As a result there will be showers and a slight chance 
for thunderstorms. The least likely place too receive thunderstorms 
will be over central Oregon on day 3. Slight chance to chance 
thunderstorms will occur elsewhere...with the greatest chance over 
the northern Blue Mountains and Wallowa County and the Grande Ronde 
Valley on Friday. The strongest winds will be in the lower Columbia 
Basin and adjacent valleys...especially on Friday. 88 

Long term...Friday night through upper level low will 
move southeast across southeast Washington and eastern Oregon Friday 
night. Instability and moisture associated with the low will trigger 
showers and thunderstorms across most of the County Warning Area...with the highest 
probability of precipitation over the eastern mountains and the east slopes of the 
Washington Cascades due to enhancement by orographic lift. An upper 
level ridge will build off the Pacific coast Saturday and Sunday. 
This will keep the area under north to northwest flow during the 
rest of the long term period. Saturday and Sunday a series of weak 
waves will move down the backside of the ridge. Daytime 
heating...instability...and lingering moisture may combine to 
trigger a few showers over the Blue Mountains and east slopes of the 
Washington Cascades during the afternoon and evening. Monday and 
Tuesday a dry and warmer conditions will build into the Pacific 
northwest due to subsidence associated with the ridge. Coonfield 


Aviation...12z tafs....VFR conditions expected for the next 24 
hours. Taf sites mainly clear with variable cirrus at kykm and kpsc. 
Winds 5-15kt increasing to 10-20 in the afternoon 76 


Preliminary point temps/pops... 
PDT 81 52 78 53 / 0 0 0 10 
alw 82 58 79 59 / 0 10 0 10 
psc 85 57 81 58 / 0 0 0 10 
ykm 82 54 78 54 / 0 0 0 10 
hri 84 55 81 56 / 0 0 0 0 
eln 80 56 77 55 / 0 0 0 10 
rdm 77 40 73 43 / 0 0 0 0 
lgd 80 47 76 49 / 10 10 0 10 
gcd 79 47 75 50 / 10 10 0 10 
dls 79 54 77 58 / 0 0 0 10 


PDT watches/warnings/advisories... 


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