377 
fxus65 kboi 200929 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
329 am MDT sun Jul 20 2008 


Short term...today through Monday...upper level wave on water 
vapor centered over far SW Idaho at 9z will lift NE through the 
central mountains this morning with some altocumulus castellanus likely exiting NE 
Valley County 15-18z. Could see a few spots of virga but 
instability is limited due to time of day. GFS only about 3 hours 
too fast with this feature compared to satellite images. Next upper 
impulse which appears to be over southern Nevada at 9z is expected to cross 
SW Idaho late this afternoon and evening on a south-southwest to north-northeast track. 
GFS seems slow in producing late day convection in the southern Idaho 
mountains with nam12 preferred...over the GFS and ec as well. Ec 
tracks the Nevada wave and attendant precipitation further east into southeast Idaho 
and has an odd spot of precipitation in the drier area between Burns and 
John Day. Thermal axis and south flow expected to warm the area 
about 4f today from Saturday...along with a bit higher dewpoints 
resulting in slightly less dry conditions mainly in the southern 
mts/Magic Valley today. Convective debris cloudiness expected to 
increase tonight and combine with warming for a very mild night. 
Slightly cooler highs Monday with additional moistening. The 
coastal low is expected to remain offshore Monday so forcing for 
late day thunderstorms is still likely to be mcvs initiated to our 
south-southwest from monsoon storms. 


Long term...Monday night through Sunday...shortwave trough... 
currently situated off the California coast...will transition north 
and east toward the forecast area on Tuesday. Tracking of this system 
now looks ideal for the northward advection of monsoonal moisture. 
Have increased confidence in thunderstorms Tuesday afternoon/evening 
ahead of this approaching system. Thus...have both expanded areal 
coverage of thunderstorms and increased probability over higher 
terrain of SW Idaho Tuesday and Tuesday night. Cooled Tuesday/S 
temperature forecast as well...as falling heights and convective 
cloud coverage will limit heating. Warmer and drier on Wednesday as 
shortwave trough exits the area and moisture shifts to our east. 
Upper level ridge regains strength by Friday...but models still 
struggling with placement of ridge axis. No changes made to next 
weekend/S forecast...as current thoughts of dry conditions and 
slightly above normal temperatures look reasonable. 


&& 


Aviation...widespread VFR under scattered middle clouds through 15z 
Sunday morning. Predominantly VFR conditions Sunday 
afternoon/evening as visibility limitations due to wildfire smoke 
will be localized. Do expect St-broken cumulus and isolated 
thunderstorms between 21z and 03z across the Idaho/Nevada border and over 
higher terrain of SW Idaho. Light surface winds...except in the 
vicinity of thunderstorms. Light southwesterly winds aloft. 


&& 


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


$$ 


Weather.Gov/Boise 


Short term...vm 
long term....Mt 
aviation.....Mt