197 
fxus65 kboi 220328 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
928 PM MDT Thursday Aug 21 2008 


Discussion...minor updates through 15z Friday. Moisture in the 
with cold advection and upslope flow into mountains brought lots 
of cloudiness north today and cumulus to the south. That cloudiness is 
beginning to dissipate and the trend will be towards clear skies 
through early Friday. Webcams and satellite imagery combined with 
hysplit runs indicates some small smoky areas through around 9 am 
Friday...on the Nevada/Idaho border near Jackpot and southeast to south 
of Atlanta and west of Fairfield. Some areas are expected to have 
mins in the 30s including west central Harney County and sheltered 
valleys in the southern Idaho mountains. This is due to light 
winds after midnight and dry air /tds in the 20s already/ there. 
So lows will be updated. 


&& 


Aviation...mostly VFR conditions tonight with clear skies by 06z. 
Surface winds will slowly decrease this evening becoming light after 
07z. After 09z local VFR with isolated IFR conditions in fog in the 
valleys of the west central mountains and near kbke. Winds aloft 
will be moderate to strong from the west. 


&& 


Previous discussion... 
short term...tonight through Saturday...strong pressure gradient 
will relax after sunset allowing gusty north westerly winds to 
diminish. Surface high pressure will be centered over Idaho on 
Friday morning bringing light winds and clear skies. This is an 
ideal set up for efficient radiational cooling... especially in 
places like McCall and Baker City where morning lows will be in 
the 30s. Patchy fog is possible early Friday morning in mountain 
valleys... especially in locations where rain occurred on Thursday. 
Friday will be sunny and mild as the upper level trough moves well 
east of the area. Temperatures will warm back up to several 
degrees above normal on Saturday as an upper level ridge begins 
building back over the area. The NAM and GFS models both hint at 
an area of moisture moving across northern Nevada on Saturday 
afternoon. We are not expecting enough moisture or instability 
north of the border to cause thunderstorm activity except... possibly 
in southern Twin Falls County... where we have indicated a slight 
change of thunderstorms on Saturday afternoon. 


Long term...Saturday night through 
Thursday...upper level ridge will continue to build into the 
intermountain west on Sunday with surface thermal trough setting 
up over the area by Sunday afternoon. Have increased Sunday 
temperatures 3 to 4 degrees as 850-700 mb thicknesses now support 
Treasure valley maximum temperatures in the upper 90s. Cooler 
temperatures and slight chances for showers on Monday as surface 
cold front will transition across the forecast area late 
afternoon/early evening. Models fairly consistent with frontal 
timing...but slight modifications may grossly affect afternoon 
temperatures. Predominantly dry on Tuesday as bulk of moisture 
will exit eastward with surface front. However...slight chances 
for showers remain across higher terrain...mainly east of McCall. 
Temperatures at or below normal Tuesday through Thursday as weak 
northwesterly flow dominates the period. 


&& 


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


$$ 


Weather.Gov/Boise 


Discussion...vm 
aviation.....Ja 
previous short term...jb 
previous long term....Mt/dd