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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Saturday
• 
• High: 68 °
• Low: 45 °
• Rain Showers

• Sunday
• 
• High: 66 °
• Low: 50 °
• Chance of Rain

• Monday
• 
• High: 66 °
• Low: 46 °
• Chance of Rain

• Tuesday
• 
• High: 68 °
• Low: 45 °
• Chance of Rain

• Wednesday
• 
• High: 68 °
• Low: 46 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Pendleton or 
825 am PDT Sat may 25 2013 


Short term...a large scale trough continues to reside over the 
Pacific northwest but forecast area is between impulses moving 
through the trough. Will see some marginal unstable conditions 
during the afternoon and early evening which could produce some 
convective showers mainly over the mountains. Otherwise a pretty 
nice day on tap with temperatures around normal today. The next 
weather impulse moving through the trough will be arriving overnight 
and Sunday. This will begin to increase clouds over the area late 
today and overnight with rain becoming likely late tonight and into 
Sunday. Temperatures will be a little cooler on Sunday due to the 
cloud cover and rain. Snow levels are expected to be between 6000 
and 7000 feet today Sunday. 


&& 


Previous discussion... /issued 449 am PDT Sat may 25 2013...updated/ 


Short term...today through Memorial Day. The Pacific northwest will remain 
under a broad upper trough with a series of waves bringing scattered 
to numerous showers. Two upper low centers are currently 
pinwheeling around each other...one located over southern Alberta 
and another near 47n/130w. Our forecast area will be located 
between these two low pressure centers today...therefore the chance 
of showers today is only about 10-30 percent with the best 
probability along the east slopes of the Washington Cascades. 
Precipitation chances increase tonight as the low over the eastern 
Pacific ejects towards the Oregon coast. By sunrise on 
Sunday...widespread rain is expected along the east slopes of the 
Oregon Cascades and as far east as Paulina. Precipitation will 
spread eastward during the day...mainly affecting our Oregon zones. 
Rainfall amounts up to 0.25 of an inch are expected...and some areas 
in the Oregon mountains could see up to 0.5 of an inch. Will keep 
the slight chance of thunderstorms over our eastern zones Sunday 
aftn/eve. Due to the amount of cloud cover on Sunday...confidence is 
not high enough to increase from slight chance to chance of 
thunderstorms. Showers will taper off from the west after the 
passage of the upper level trough Sunday night. Another shortwave 
trough is prognosticated to swing across Oregon and southern Washington on 
Memorial Day...bringing another round of scattered to numerous 
showers. Once again...the best chance of precipitation on Memorial 
Day will be along the east slopes of the Oregon Cascades and most of 
central Oregon. Wister 


Long term...Monday night through Saturday...the next upstream 
weather system is forecast to move into the Pacific northwest as a 
negative tilt trough by both the GFS and European model (ecmwf) Monday night. This 
system will bring a surge of moisture that will pivot around the 
base of the trough from western Oregon/Washington east-northeast 
across the eastern areas of the Pacific northwest. As a result there 
should be a pretty good chance of precipitation over the entire County Warning Area 
Monday night into Tuesday along with cooler temperatures again. 
However snow levels will remain high enough to negate any winter 
weather concerns over the mountain passes in the County Warning Area with snow 
levels up around 6500-7500 thousand feet mean sea level. Precipitation along 
the areas east of the Cascades will see some decrease in due to 
downslope winds off the Cascades by Tuesday night. There will be an 
overall decrease in precipitation from Wednesday Onward as the 
weather system stretches and weakens. However an overall trough 
pattern will remain over the forecast area through Friday with 
mainly mountain showers continuing. A drier northwest flow will then 
develop by Saturday with improving conditions and the beginning of a 
warming trend in time for the weekend. The atmosphere will be too 
stable throughout the extended period for any thunderstorm threat. 88 


Aviation...12z tafs...VFR conditions will prevail through the next 
24 hours. There will be a break in the weather today with dry 
conditions at all taf sites. Then another weather system will move 
into the area tonight with increasing chances of showers at all taf 
sites...especially krdm...kbdn and kdls. Winds will be light and 
under 10 kts this morning but will increase to 10-15 kts this 
afternoon and early evening. Winds will diminish to less than 10 kts 
again by 06z tonight at most taf sites. 88 


&& 


Preliminary point temps/pops... 
PDT 68 46 63 47 / 10 10 60 20 
alw 69 49 65 51 / 10 10 60 30 
psc 72 48 67 50 / 10 10 50 20 
ykm 68 46 63 49 / 10 20 50 20 
hri 71 48 66 51 / 0 10 60 20 
eln 66 44 60 46 / 10 20 50 20 
rdm 65 42 57 40 / 10 70 80 10 
lgd 65 41 57 41 / 10 10 70 40 
gcd 64 43 55 40 / 10 50 60 30 
dls 69 49 62 51 / 10 50 70 10 


&& 


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


Threat index 
today : green 
Sunday : green 
Monday : 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