366 
fxus66 kpdt 220535 aaa 
afdpdt 


Area forecast discussion...updated 
National Weather Service Pendleton or 
1035 PM PDT sun Mar 21 2010 


Updated aviation discussion 


Short term...tonight through Tuesday. Forecast on track and only 
updates planned will be to remove evening thunderstorms and breezy 
winds with minor changes to temperatures in a few zones. Showers 
and isolated thunderstorms have tapered off after sunset. Due to a 
weak cyclonic flow and a westerly flow aloft over the Pacific 
northwest...showers will remain over the mountains with light precipitation 
amounts. Snow levels will lower to around 3000 feet overnight with 
a couple of inches possible on the west facing slopes of the Blue 
Mountains. Tomorrow will see a westerly flow into the mountains so 
showers should continue through the day in the foothills and 
mountains while the Columbia Basin is dry. Tomorrow will be a few 
degrees cooler with a colder air mass overhead. By tomorrow 
night...showers will have tapered off virtually nothing while a 
ridge rebuilds over the region. Dry weather will continue through 
Tuesday with a warmer temperatures. Johnson/Perry 




&& 


Aviation...06z tafs. A few brief rain showers may develop over the 
taf sites in the next hour or two. Precipitation will end overnight 
along with a break in cloud cover. On Monday...skies will be 
scattered-broken with bases forecast to be around 050-090. Winds will 
generally be less than 15 knots...although gusts to around 25 knots 
are expected at kdls on Monday. Johnson 


&& 


Previous discussion... /issued 230 PM PDT sun Mar 21 2010/ 


Long term...Tuesday night through Friday night. Models in fairly 
good agreement through the midterm with ridge and dry condition 
Wednesday. The system will approach the coast by late Wednesday and 
become negatively tilted as it moves into the area Wednesday night 
and Thursday. The region remain under at large scale trough through 
Friday with another low pressure area expected to move through the 
area on Friday. Temperatures are expected to be above normal 
through Wednesday and cool to below normal values through Friday as 
the systems bring in some cooler air from the north. Ml 


Saturday through Sunday night...models are in fair agreement of an 
upper level ridge over the area Saturday. However...the strength and 
amplitude is still questionable by models. Expect Saturday to be 
mainly dry...except for the slight chance of a shower along the east 
slopes of the Cascades or in Wallowa County. The next chance for 
showers will be Sunday as an upper level low pressure system pushes 
in off the Gulf of Alaska. It is possible that the precipitation may 
hold off till late Sunday night or Monday morning...as models differ 
in the breakdown of the ridge. GFS has a quick moving trough ahead 
of the low pushing through on Sunday and bring widespread showers to 
the area. European model (ecmwf) indicates the low off the goa as well but showers 
not indication in the last several runs of a trough ahead of this 
low. So did not go too aggressive with probability of precipitation in day 7...but kept a 
chance across the area. Temperatures still look to be in the upper 
50s to lower 60s across the lower elevations and in the upper 40s to 
50s mountains. If southerly flow continues as models 
indicate...Saturday and Sunday morning lows should be in the upper 
30s to lower 40s for the lower elevations and in the upper 20s to 
middle 30s mountains. Weber 


Aviation...00z tafs...areas of rain will become more showery through 
the evening with a few showers continuing at kpdt and kalw through 
03z. Ceilings between 5000 to 7000 feet will be clearing from west 
to east across the region starting at about 02z...with ceiling above 
10000 feet expected by Monday morning. Winds will be under 10 knots 
overnight...but are expected to increase to 10 to 20 miles per hour after 16z 
Monday. Ml 


&& 


Preliminary point temps/pops... 
PDT 38 53 33 60 / 50 20 10 0 
alw 41 55 36 61 / 50 20 10 0 
psc 38 60 33 62 / 30 10 0 0 
ykm 35 57 31 62 / 20 10 0 0 
hri 37 59 31 63 / 40 10 10 0 
eln 35 55 31 60 / 30 20 10 0 
rdm 26 50 21 61 / 20 20 10 0 
lgd 36 48 28 57 / 60 30 10 0 
gcd 33 46 28 59 / 60 40 10 0 
dls 39 57 35 63 / 30 20 10 0 


&& 


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


Threat index 
Monday : 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 


$$ 


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