699 
fxus65 kboi 282028 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
230 PM MDT Thursday Aug 28 2008 


Short term...westerly flow of dry air continues over the area 
tonight and Friday as Pacific high pressure continues to dominate. 
Much warmer temperatures returning to the region Friday as the 
thermal trough rebuilds along the West Coast and gradually slides east 
during Saturday. This could make Saturday very tricky for 
temperatures...wind and min relative humidity which of course has implications for 
fire weather. Right now we are favoring slower timing to the upper 
trough and frontal passage Saturday evening as the upper trough sharpens 
up along the West Coast bringing southerly flow aloft into the area. 
Thus...the temperature spread of solutions for Saturday is wide 
ranging...but with a slower evolution and eastward progression to 
weather features...a warmer scenario for Saturday may be the most 
correct. Probability of precipitation are minimal on Saturday and confined to kpdt and kmso 
areas at this time. A better chance for precipitation starts in the 
extended portion Saturday night and especially Sunday as 
baroclinicity increases over the forecast area as the upper trough 
deepens in the Pacific northwest and a better structured frontal 
system takes shape. 


Long term...Saturday night through Thursday...active weather and 
cooler temperatures through the weekend into early next week as the 
pattern shifts towards a fall type pattern. Models remain in good 
agreement in bringing a deep trough into the northwest early Sunday 
though the last three model runs have been much quicker in timing. 
Temperatures drop quickly as trough moves over the region with 
Monday expected to be the coldest day. High temperatures Sunday will 
be 10-13 degrees cooler across the entire area from Saturday in the 
wake of the cold frontal passage Saturday. Upper level trough 
settles over the County Warning Area on Monday with models showing it will become a 
closed low over the area. Fall like temperatures on Monday as 556 to 
560 dm 500 mb heights over the region suggest temperatures in the 
middle 60s to low 70s. Not much in the way of moisture with the trough 
initially...until it taps into monsoonal moisture flowing up from 
the south on Sunday. Models showing a majority of this moisture will 
stay over eastern Idaho into Montana and Wyoming. Newer model runs 
showing moisture further west mainly into the central mountains of 
Idaho and southwestern Idaho mountains. Have adjusted probability of precipitation 
accordingly but further adjustments maybe needed if models continue 
to trend a more westerly shift of moisture. Region will stay in 
broad cyclonic flow Tuesday through Thursday as another weaker 
trough drops down from Canada into the Bitterroot Mountain region. 
Temperatures look to remain at or slightly below normal middle week. 


&& 


Aviation...VFR conditions under mostly clear skies tonight and 
tomorrow. Pilots reported MVFR conditions up to 10 kft this 
afternoon from smoke plumes around wildfires near Featherville 
Idaho...Jackpot Nevada and Picabo Idaho. Prevailing northwest winds 
has pushed smoke into the Magic Valley causing MVFR conditions 
between 8kft and 10kft. Smoke could become trapped in mountain 
valleys tonight as inversion setup for IFR to MVFR conditions. 
Surface winds will be light with light to moderate west northwest 
winds aloft. 


&& 


Boi watches/warnings/advisories... 
Idaho...none. 
Or...none. 
&& 


$$ 


Weather.Gov/Boise 




Short term...gs 
long term....js/LH 
aviation.....Js