854 
FXUS65 KBOI 020955
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
255 AM MST Tue Jan 2 2018

.SHORT TERM...Today through Wednesday...An upper level ridge axis
will remain nearly stationary over the region through the short
term period. This will allow the inversion to strengthen. Mid and
upper level moisture will increase tonight into tomorrow, bringing
an increase in cloud cover and moderating the diurnal range (the
difference in the high and low at any one location). Fog/stratus
is expected to develop in/near the Lower Treasure Valley and
spread into the western end of the Upper Treasure Valley (Ada
County and perhaps along the Snake River into Elmore County) today
into tomorrow, but the initiation of this is always difficult to 
time. Changes to the previous forecast were small.

.LONG TERM...Wednesday night through Monday...The upper level 
ridge's strength will begin to be tested as early as Thursday as a 
series of troughs move into the Intermountain West. The models seem 
to have the first two troughs break down as they endeavor to move 
into the ridge Thursday and Friday, but Saturday's system seems 
promising in that it should be cool enough aloft to flush out all 
remaining valley inversions. Precipitation will be light with the 
first two troughs both Thursday and Friday, but look to increase 
with Saturday's system. Have indicated areas of freezing rain 
Thursday with cold air likely still trapped in the lower valleys. A 
ridge will build in behind Saturday's system bringing dry conditions 
back to the region. Temperatures will start below normal in the 
inverted valleys and above normal elsewhere on Thursday and slowly 
return to near normal through the extended forecast.

&&

.AVIATION...VFR and mostly clear. Patchy valley fog with areas of 
MVFR/IFR fog possible through 02/18Z. Light surface winds. Winds 
aloft near 10KFT MSL: north around 10 kts, becoming variable 5-10 
kts by 02/18Z.

&&

.AIR STAGNATION...Surface inversion is strengthening the next two
days. Air quality should continue to decline. Best chance for
breaking the inversion will come Friday into Saturday with an 
upper level system and associated front.


&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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SHORT TERM...SP
LONG TERM....AB
AVIATION.....AB
AIR STAGNATION...SP