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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 66 °
• Low: 50 °
• Rain Showers

• Thursday
• 
• High: 64 °
• Low: 48 °
• Chance of Rain

• Friday
• 
• High: 75 °
• Low: 46 °
• Chance of Rain

• Saturday
• 
• High: 77 °
• Low: 57 °
• Clear

• Sunday
• 
• High: 90 °
• Low: 57 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Pendleton or 
1018 PM PDT Tuesday Jun 18 2013 


Updated aviation discussion 


Short term...tonight and Wednesday...upper level low pressure 
system that had been off the coast began to move inland today. What 
was expected to be a convective thunderstorm type of a day failed to 
materialize due to the extensive cloud cover over the forecast area 
which kept temperatures cool. Did see some isolated thunderstorms 
this evening over central Oregon and could still see some isolated 
thunderstorms into early tonight but then overnight just expecting 
showers. Forecast has been updated to reflect this. The upper low 
will be centered over the forecast area on Wednesday so with any 
surface heating there will be the development of showers and 
possible thunderstorms. Temperatures will remain cool and there will 
be some increasing westerly winds. 


Aviation...06z tafs...upper level low will remain over the region 
for the 24 hours providing middle level clouds and showers. Expect 
mainly VFR conditions but will see MVFR or lower conditions in 
vicinity of showers and thunderstorms. West winds will increase on 
Wednesday for all sites becoming 10-20 knots with gusts over 30 
knots. 


&& 


Previous discussion... /issued 400 PM PDT Tuesday Jun 18 2013/ 


Short term...tonight through Friday. The Pacific northwest will be 
influenced by a large vertically stacked low through the short term 
period. The low is offshore and will be tracking inland tonight then 
east of the Cascades Wednesday morning. The low will continue to 
spin over Washington/or/ID through the remainder of the period. The NAM was 
the outlier of all the models by pushing the closed low eastward 
Thursday night and was disregarded in the forecast. 


There is an extensive cloud cover over the forecast area that is 
limiting the amount of surface heating. Several weak embedded 
thunderstorms have developed over central Oregon. Water vapor shows 
a wave over northwest California that will swing northeast this evening and 
should bring scattered thunderstorms across our eastern zones. A 50 
knot middle level jet and strong shear will provide middle level ascent 
for organized convection. Current forecast...hazardous weather 
outlook...and graphical weather stories highlight the potential for 
penny to nickel size hail and isolated gusts to 50 miles per hour in eastern 
Grant, Union, and Wallowa counties. Isolated to scattered 
thunderstorms will continue in this area even after midnight. 


It will be cool and showery Wednesday through Friday. Afternoon 
temperatures will be about 10-20 degrees below seasonal averages. 
Snow levels will lower to around 6000-6500 feet. A Special Weather 
Statement was issued to alert campers and hikers of snow in the 
higher terrain of the Cascades and The Wilderness regions of eastern 
Oregon. The cold upper low will also bring isolated to scattered 
thunderstorms. All areas in our County Warning Area have a potential to observe 
thunderstorms on Wednesday...and the threat will mainly be in our 
eastern zones Thursday through Friday. Thunderstorms are not 
expected to be strong or severe but should produce small hail. Wister 


Long term...Friday night through Tuesday...mid/upper level low 
still lingering over Idaho/Montana thus keeping western flank of low 
and attendant wrap around moisture streaming across mountains of southeast 
Washington and NE Oregon Friday evening for a chance of showers. 
Probability of precipitation decrease overnight and Saturday as the low finally eases 
eastward into central Montana with a middle/upper level ridge of high 
pressure building over forecast area on Saturday for dry conditions. 
Sunday. Saturday night/Sunday the next upstream middle/upper level 
Pacific trough moves to coast and pushes a cold front with 
increasing moisture east of Cascades for chance of showers mainly 
along east slopes of Cascades and in Blue Mountains. Monday and 
Tuesday a large middle/upper level low in NE Pacific causes flow aloft 
to back to the southwest thus bringing a moist middle level air mass 
into forecast area which becomes marginally unstable in the 
afternoon/evening on Monday and Tuesday for a slight chance of 
afternoon/evening thunderstorms over the eastern mountains. Polan 






&& 


Preliminary point temps/pops... 
PDT 53 64 48 66 / 70 70 40 40 
alw 56 62 52 66 / 80 70 50 40 
psc 56 69 53 69 / 60 50 40 40 
ykm 54 69 51 65 / 40 40 40 40 
hri 56 68 52 69 / 60 50 40 40 
eln 53 67 51 63 / 50 40 40 40 
rdm 44 60 37 66 / 60 40 30 20 
lgd 49 56 44 60 / 90 90 60 40 
gcd 47 55 40 61 / 80 70 50 30 
dls 56 68 52 69 / 40 40 40 30 


&& 


PDT watches/warnings/advisories... 
or...none. 
Washington...none. 
&& 


Threat index 
Wednesday : green 
Thursday : green 
Friday : green 


Green: none or limited need for watches, warnings, or advisories. 
Yellow: a few watches, warnings, or advisories possible or in effect. 
Red: numerous watches, warnings, or advisories possible or in effect. 


For additional weather information, check our web site at... 
www.Weather.Gov/Pendleton 


$$ 


91/76/76