Area forecast discussion 
National Weather Service Pendleton or 
1030 PM PDT Sat may 18 2013 


Short term...upper level trough is moving across the region this 
evening. Skies are partly to mostly cloudy with isolated showers. 
With loss of heating after sunset precipitation will decrease to a 
few showers over the Cascades and blues. Breezy westerly winds will 
also diminish overnight. Upper level ridge will result in mostly 
sunny skies and warmer temperatures Sunday and Monday. 94 


Aviation...06z tafs. Scattered-broken 050-080 tonight as a weak upper trough 
is moving through. Scattered 050-080 Sunday. Winds 5-15kt except 10-20kt 
at dls. 94 


&& 


Previous discussion... /issued 330 PM PDT Sat may 18 2013/ 


Short term...tonight through Monday night...a weak Pacific system 
will continue to move across the region tonight. This system will 
then shift southeast across Idaho and Wyoming on Sunday. Will 
continue to see isolated to scattered showers across much of the 
area this evening, with the best chances across central and 
east-central Oregon. These showers will gradually decrease late this 
evening and overnight, with only a few showers lingering over the 
mountains towards daybreak. There remains enough instability late 
this afternoon into early this evening for stray thunderstorms over 
the southern Oregon Blue Mountains, the John Day basin and the John 
Day-ochoco Highlands. Winds will continue breezy to locally windy 
across the area through this evening, then gradually decrease 
overnight. Locally breezy winds will continue through Sunday, 
primarily in and near the Columbia River gorge and in the Kittitas 
Valley. Lingering moisture combined with a northwest flow aloft will 
keep a few showers going over some area mountains Sunday through 
Sunday evening due to upslope affects. Otherwise high pressure aloft 
and at the surface will build into the region Sunday night into 
Monday. Thus expect dry conditions late Sunday night through Monday 
evening. High temperatures Monday will warm 7-10 degrees over Sunday 
afternoon. An approaching Pacific system may spread some light 
precipitation to the Washington Cascade crest area late Monday night, 
otherwise should continued dry conditions with increasing clouds. 90 


Long term...Tuesday through Saturday. Confidence is high that the 
Pacific northwest will be under the influence of a large closed low during 
the period. However...confidence in the exact placement of the low 
and the location/strength of embedded shortwaves is low...especially 
thurs-Sat. The large upper low will move onshore Tuesday then will 
become blocked by an amplified ridge over the Midwest. This cold 
low will result in unseasonably colder temperatures and showery 
conditions through the extended period. Snow levels will lower 
significantly late Tuesday night and Wednesday morning...possibly as 
low as 3500-4000 feet. Models begin to diverge on Thursday. While 
the European model (ecmwf) swings the low to the northeast across Oregon on 
Friday...the GFS is farther north and west with the primary position 
offshore. Either way...the Pacific northwest will be cool and showery 
during the long term period. Wister 


&& 


Preliminary point temps/pops... 
PDT 46 70 44 76 / 20 10 0 0 
alw 50 71 49 77 / 20 10 0 0 
psc 48 77 42 80 / 20 10 0 0 
ykm 42 74 40 78 / 20 10 0 0 
hri 48 75 41 79 / 20 10 0 0 
eln 46 72 43 78 / 20 10 0 0 
rdm 35 67 32 76 / 20 10 0 0 
lgd 44 65 40 73 / 30 20 0 0 
gcd 40 67 36 76 / 30 10 0 0 
dls 50 71 44 81 / 20 10 0 0 


&& 


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


Threat index 
Sunday : green 
Monday : green 
Tuesday : 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 


$$ 


94