415 
fxus66 kpdt 070538 aaa 
afdpdt 


Area forecast discussion...updated 
National Weather Service Pendleton or 
1038 PM PDT Sat Sep 6 2008 


Updated aviation discussion 


Short term...an upper ridge remains off the West Coast with an axis 
roughly along 135w at the moment. As a result the Pacific northwest 
remains under a mostly dry northwest flow aloft. What cloud cover 
there has been over southeast Washington and northeast Oregon late 
this afternoon and this evening continues to dissipate. The 
dissipation of the cloud cover has been slow as a weak upper wave 
imbedded within the upper flow has been keeping some cloudiness 
going despite the loss of daytime heating. Once this wave exits the 
area early Sunday the last of these clouds should disappear. Winds 
are generally light...though winds around 10-15 miles per hour will continue 
for another hour or two in the Kittitas Valley and the eastern 
Columbia River gorge. Updates this evening where to adjust some wind 
and sky cover wording...otherwise forecast trends are on track. 90 


Long term...previous discussion...GFS and European model (ecmwf) models and 
ensembles show a similar long wave pattern through the long term 
period for higher than normal confidence. Dry northwest flow on the 
backside of an offshore long wave ridge will persist Tuesday night 
and Wednesday. Winds will be breezy in the Columbia Basin and 
Kittitas Valley Tuesday night as an upper level disturbance over the 
ridge from northern Washington into Idaho and Montana. The ridge 
will flatten out and nudge into the Pacific northwest Wednesday 
night through Friday as a series of upper level disturbances move 
over the top of the ridge in Canada. Higher heights and subsidence 
aloft associated with the ridge will keep dry and stable westerly 
flow over southern Washington and Oregon. The subsidence will keep 
winds light. The subsidence will also create a warming trend during 
the day...but lengthening nights and light winds will allow surface 
inversions and good radiational cooling to develop at night. Friday 
afternoon (ecmwf) or evening (gfs) a dry cold front will move 
through and bring cooler temperatures Saturday. 


&& 


Aviation...06z tafs...upper high pressure will shift onshore during 
the next 24 hours. This will keep conditions VFR with mostly clear 
skies. Sustained surface winds will be generally 10 kts or less 
through the period. 90 


&& 


Preliminary point temps/pops... 
PDT 51 80 49 81 / 0 0 0 0 
alw 54 81 53 82 / 0 0 0 0 
psc 51 84 49 84 / 0 0 0 0 
ykm 51 82 50 82 / 0 0 0 0 
hri 48 82 46 83 / 0 0 0 0 
eln 49 81 48 83 / 0 0 0 0 
rdm 43 81 41 83 / 0 0 0 0 
lgd 45 77 43 81 / 0 0 0 0 
gcd 46 79 46 84 / 0 0 0 0 
dls 56 85 53 87 / 0 0 0 0 


&& 


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


$$ 


Ti:ggg 
for additional weather information, check our web site at... 
www.Weather.Gov/Pendleton 
90/76/90