374 
fxus65 kboi 230949 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
250 am MST Monday Nov 23 2009 


Short term...today through Tuesday...high pressure building over 
the forecast area for benign weather the next two days. However...a 
weak disturbance is forecast to slide southward late tonight from 
the Pacific northwest...eventually washing out over central Idaho 
within the building upper ridge. Models handling this feature 
slightly differently with the NAM more aggressive showing a more 
southerly position and limited probability of precipitation...while the GFS keeps the 
feature north of our forecast area in central Idaho across the 
Salmon river and points north. Have chosen a compromise between the 
two and allowed a smattering of slight chance probability of precipitation across Baker 
County Oregon and Valley County Idaho late tonight and Tuesday. 
Otherwise...with the above mentioned ridge taking hold...weather 
remains quiet with a good amount of sunshine today and partly to 
mostly cloudy skies Tuesday. Temperatures cool today with surface 
based inversion strengthening...but warming becoming more 
significant Tuesday as high center drifts over eastern Idaho 
bringing easterly component flow back to our region aiding low level 
warming. 


Long term...Tuesday night through Monday...the pattern through the 
period is progressive. Model agreement and run to run consistency 
are quite good through Friday. A ridge over our area Wednesday moves 
east of The Rockies Thursday followed by a shortwave trough crossing 
the region Thursday night through Friday night. Over the weekend the 
Canadian diverges from the gfs40/GFS ensemble mean/European model (ecmwf) by bringing 
US a much colder pattern with a ridge building offshore rather than 
over the West Coast states. We are staying with the milder 
guidance...with temperatures 5 to 10 degrees above normal on 
Thanksgiving day...cooling to near normal for Saturday through 
Monday. Best chances of precipitation will be with the trough 
passage Thursday night through Friday night. For the rest of the 
period probability of precipitation will be below normal for our southern zones and near 
normal for Baker County and the west central Idaho mountains. 


&& 


Aviation...local MVFR ceilings and areas of terrain obscuration 
will persist in the west central Idaho mountains through this 
morning. Otherwise expect VFR conditions today through Tuesday. 
With an inversion intensifying tonight through Wednesday...patchy 
night and morning fog will be possible in mountain valleys... 
especially late Tuesday night and Wednesday morning. Surface winds 
will be light today. Winds aloft will be light to moderate 
northwest. 


&& 


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


$$ 


Weather.Gov/Boise 


Short term...gs 
long term....jt/Mt 
aviation.....Jt