685 
fxus66 kpdt 112247 
afdpdt 


Area forecast discussion 
National Weather Service Pendleton or 
247 PM PST Thursday Mar 11 2010 


Short term...tonight through Saturday...an active and busy weather 
period is in store for the next couple of days as a complex weather 
system sets up along the coast and eventually moves through the 
area. Currently a trough is developing off the Pacific northwest 
coast. A frontal system is just off shore and is stalled along the 
Cascades. A moist southwesterly flow is overrunning cooler air at 
the surface and creating rain and mountain snow showers. This 
evening the showers will expand east to the Blue Mountains. As an 
upper low moves towards the coast tonight it will dig the trough 
southward and this will actually pull the front west towards the 
coast and decrease the showers to a slight chance in the eastern 
Columbia Basin overnight. As the low approaches...pressure gradients 
will tighten and the southern Grande Ronde Valley will see 25 to 35 
miles per hour winds...mainly in Ladd and Pyles Canyon. The current Wind 
Advisory through tomorrow afternoon looks good. Winds will also 
increase in the Blue Mountain foothills to 15 to 25 miles per hour late tonight 
and tomorrow morning but should remain below Wind Advisory levels. 
After pulling back to near the Cascades tomorrow morning...rain will 
spread across the area in the afternoon. Models show up to three 
quarters of an inch of liquid precipitation in the Blue Mountains 
and Wallowa County with a quarter inch or so in the rest of the 
mountains and the Blue Mountain foothills by Saturday morning. Snow 
levels will drop to around 3500 feet Friday night in the eastern 
mountains so a Winter Storm Watch has been issued for Wallowa County 
and the Blue Mountain zones above 4000 feet where anywhere from 4 to 
9 inches of snow is anticipated. The trough will move across the 
area Saturday and as it does so...the precipitation will become more 
showery and taper off to just the far eastern mountains by the 
afternoon. Perry 


Long term...Saturday night through Tuesday night. High pressure 
will dominate the areas weather with dry conditions into Monday. The 
next storm system to effect the region is expected on Tuesday. Low 
pressure is forecast to track across Washington/or increasing the chance for 
showers into Tuesday night. 


Afternoon high temperatures are expected to be near normal Sunday. A 
slight warming trend is likely for the beginning of the week as high 
temperatures approach 60 degrees across portions of the basin. 97 


Wednesday through Thursday night...as an upper level disturbance 
pushes off to the northeast...shower activity should be minimal 
along the mountains of northeast Oregon. Westerly flow will set in 
and conditions should be fairly dry across the County Warning Area much of Wednesday 
afternoon and into the overnight hours. Another disturbance will 
push down from the Gulf of Alaska Thursday morning. However...models 
are not in total agreement as to if this system will ride over the 
area and affect the Idaho/Montana area. This being the case 
conditions Thursday should be mostly dry and cool with northwest 
flow. If the system pushes down over the County Warning Area then can expect all 
areas to have a chance for rain/snow showers. Weber 


&& 


Aviation...000z tafs...clouds will continue to increase this 
evening with showers persisting tonight. Local VFR conditions will 
deteriorate to areas of MVFR ceilings in showers through the night 
and into tomorrow morning. In addition south to southwest winds 
between 15 to 25 kts are likely at taf sites kpdt...kalw into this 
evening and then decrease some overnight before returning again 
Friday morning. Ceilings may improve and local VFR conditions possible 
before another storm system takes aim on our area creating areas of 
MVFR/IFR ceilings and visibility toward into Friday evening. 97 


&& 


Preliminary point temps/pops... 
PDT 41 57 34 50 / 30 50 60 20 
alw 43 58 37 53 / 30 50 70 20 
psc 41 58 35 55 / 30 60 50 10 
ykm 37 54 31 53 / 30 70 30 10 
hri 39 58 33 55 / 30 50 50 10 
eln 37 52 31 51 / 40 80 30 20 
rdm 35 50 23 48 / 30 50 50 20 
lgd 37 51 31 45 / 20 30 70 30 
gcd 35 49 30 45 / 20 40 80 30 
dls 40 51 34 53 / 40 70 40 20 


&& 


PDT watches/warnings/advisories... 
or...Winter Storm Watch from Friday morning through Saturday 
afternoon above 3500 feet for the orz502-503. 


Wind Advisory until 4 PM PST Friday orz049. 


Winter Storm Watch from Friday morning through Saturday 
afternoon above 4000 feet for the orz050. 


Washington...Winter Storm Watch from Friday morning through Saturday 
afternoon above 3500 feet for the waz030. 


&& 


Threat index 
Friday : yellow 
Saturday : green 
Sunday : 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 


$$ 


83/97/89/97