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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 72 °
• Low: 46 °
• Rain Showers

• Thursday
• 
• High: 70 °
• Low: 43 °
• Chance of T-Storms

• Friday
• 
• High: 73 °
• Low: 43 °
• Partly Cloudy

• Saturday
• 
• High: 75 °
• Low: 50 °
• Partly Cloudy

• Sunday
• 
• High: 73 °
• Low: 50 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Pendleton or 
815 am PDT Wednesday may 23 2012 


Short term...today and tonight...the region is under a cool and 
unstable northwest flow. This will result in an upslope flow into 
the Cascades and eastern mountains through the day for favored 
precipitation areas. Expect instability to increase with the 
heating of the day so showers will increase into the afternoon and 
evening. Shower activity will then be on the decrease around sunset 
and overnight. A slight chance of thunderstorms exists over 
northeast Oregon and southeast Washington. Temperatures will 
continue to run below normal today and breezy west winds will make 
it feel even cooler. Winds decrease overnight. 




&& 


Previous discussion... /issued 300 am PDT Wednesday may 23 2012/ 


Short term...today through tomorrow night...upper low continues to 
deepen over the forecast area over the next 48 hours. Expect a 
chance of showers along the mountains and a slight chance of 
afternoon and evening showers over the lower elevation. There is 
some question about todays thunderstorms potential...mainly along 
the foothills eastward. Models differ on surface moisture and NAM 
has an inversion around 600mb capping off the cloud tops. 
However...GFS inversion is weak and negligible...since surface 
dewpoints and temperatures remain higher. GFS instability may even be 
enough to get some small hail out of the thunderstorms. Due to the 
decent amounts of moisture over the past couple of days and that the 
NAM model data seems to be conservative on the low level moisture 
and temperatures...have decided to add slight chance thunder over 
these areas from 11am to 5pm...with the thunderstorm potential after 
5 PM being mainly over Wallowa County. Temperatures today should be 
close to yesterdays highs...since the airmass aloft has not changed 
much. 


Tomorrow will continue the threat for showers across all areas. 
With the low deepening over the Pacific coast...areas east of the 
Cascades will be under southerly flow aloft. Surface moisture will 
be similar to previous days and maximum temperatures are expected to 
be similar to wednesdays. 850 to 500 mb temperatures differ by -30c 
across all areas...and with negative lifted indice's across all areas as well. 
Thus have expanded slight chance thunder to include all areas 
through 5 PM Thursday. By late afternoon to early evening the east 
slopes of the Oregon Cascades and the Deschutes...Crook County area 
can expect for much cooler stable conditions to set in...and 
therefore have been transitions from thunder showers to stratiform 
rain...with high elevation snow possible. GFS sets up a decent 
deformation zone over this area after 5 PM and supports high quantitative precipitation forecast 
amounts for the evening and overnight hours. Will have to monitor 
the temperatures...snow levels...and quantitative precipitation forecast amounts to see if any 
highlights might need to be issued. Weber 


Long term...upper low will move south of the area Friday into early 
Saturday before moving NE into Idaho and Montana over the weekend. This will 
keep rain chances over mainly the southern and eastern portion of 
the forecast area Friday and into the weekend...with the best chance 
for precipitation on Friday. There could be a little snow mixed in 
with the rain above 5000 feet Friday morning over the Central 
Highlands. Also on Friday afternoon and evening there will be a 
slight chance for thunderstorms. As the upper low exits the region 
another storm system will move into the region Monday bringing 
breezy conditions and a chance of rain mainly over the mountains. A 
ridge of high pressure will then build over the area by middle week 
with moderating temperatures. Until then expect near to slightly 
below normal temperatures. 78 


Aviation...12z tafs...VFR conditions will prevail through 12z 
Thursday. Expect scattered-broken cumulus/SC at 4-5k feet and broken ceilings at 7-8k 
feet for much of the period. Peak in cloud cover will be from 
18z-03z with scattered showers. Will carry vcsh at the taf sites 
this afternoon. It will be breezy to windy through this evening with 
west winds of 15 to 25 knots and higher gusts. Winds will be erratic 
and gusty near convective showers. 78 


&& 


Preliminary point temps/pops... 
PDT 62 44 63 43 / 40 40 50 40 
alw 63 46 63 47 / 40 40 50 30 
psc 67 47 67 47 / 20 20 30 30 
ykm 64 44 63 46 / 20 20 30 30 
hri 65 44 66 46 / 20 20 40 30 
eln 63 43 62 45 / 20 20 40 30 
rdm 58 34 56 36 / 20 20 60 60 
lgd 54 39 55 41 / 50 50 60 50 
gcd 52 34 52 41 / 40 40 60 40 
dls 64 48 64 48 / 20 20 50 30 


&& 


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


Threat index 
today : 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