589 
fxus66 kpdt 231142 
afdpdt 


Area forecast discussion...updated 
National Weather Service Pendleton or 
345 am PST Monday Nov 23 2009 


..updated aviation discussion... 


Short term...today through Tuesday night...a weak upper ridge will 
be over the region today. Thus should see mostly dry conditions with 
variable amounts of high cloudiness today. There will be few showers 
drift over into the central Washington Cascade east slopes from 
western Washington this morning. A disturbance in the eastern Gulf 
of Alaska will move towards northwest Washington this afternoon. 
This system should increase cloudiness and bring a better chance of 
light precipitation to the central Washington Cascade east slopes this 
afternoon. This disturbance will move east across northern 
Washington and southern British Columbia into Montana tonight and 
Tuesday. As a result there should be varying chances of mostly light 
precipitation over southeast Washington and northeast Oregon tonight into 
Tuesday. At this time expect our central Oregon zones to stay dry. 
By Tuesday afternoon precipitation should be limited to lingering mountain 
showers. Another upper ridge looks to build Tuesday afternoon and 
Tuesday night. This ridge would push the main storm track northwest 
of our region with only a slight chance of very light precipitation over 
the central Washington Cascade east slopes. This ridge looks to be 
strong enough to develop strong low level inversions over the 
Columbia Basin. As such will keep some mention of patchy fog and 
freezing fog for late Tuesday night below 900 feet mean sea level in the basin 
and Columbia River gorge. 90 


Long term...Wednesday through next Sunday...high pressure aloft 
will gradually build stronger over the region for most of this week. 
A weak cold front will cross the region on Tuesday but will be 
pushed back up north by the strengthening upper ridge. This will 
keep moisture and Pacific weather systems mainly the north of the 
County Warning Area with just a few middle and high clouds over the forecast area. Then 
next weather system to affect the region will arrive by Thursday 
night and continue until Friday...first as a warm front quickly 
followed by a cold front. This feature will bring a small amount of 
precipitation to the area as it will be moving fast with an upper 
jet pushing it eastward quickly and perpendicular to the cold front. 
This will be followed by high pressure over the region again for 
Saturday and Sunday. 88 


&& 


Aviation...12z tafs...VFR conditions will prevail through the day 
today with middle and high clouds. Another weather disturbance will 
move into the area overnight tonight with another chance of rain and 
mountain snow. This will mainly affect northeast Oregon and eastern 
Washington. Taf krdm in central Oregon will likely not see any 
precipitation from this system. There may be brief periods of MVFR 
or even IFR tonight in rain/snow showers...especially at kdls...kykm 
and kpsc...and to a lesser degree at kpdt and kalw. Winds of 10 to 
20 kts this morning will gradually continue to decrease today. The 
wind is not expected to increase much with this next system... but 
perhaps 15 to 25 kts at times...especially near showers and with the 
cold front passage. 88 


&& 


Preliminary point temps/pops... 
PDT 47 34 48 33 / 0 20 20 0 
alw 47 36 47 35 / 0 20 20 0 
psc 48 34 47 32 / 10 20 10 0 
ykm 44 28 46 30 / 10 30 20 0 
hri 49 32 48 31 / 0 20 10 0 
eln 43 30 45 31 / 10 30 20 10 
rdm 46 26 50 25 / 0 10 10 0 
lgd 40 29 44 27 / 0 20 20 0 
gcd 43 27 47 27 / 0 10 10 0 
dls 46 35 48 37 / 10 30 20 0 


&& 


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


Threat index 
today : green 
Tuesday : green 
Wednesday : 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 


$$ 


90/88/88