FXUS65 KBOI 031718

AFDBOI



Area Forecast Discussion

National Weather Service Boise ID

1018 AM MST Tue Feb 3 2026



.DISCUSSION...Satellite is revealing several layers of cloud 

cover this morning. We'll continue to see periods of clouds

today with moisture rolling over the top of the ridge. Morning

fog/haze will improve some over lower valleys with the limited

mixing we see today. We're still looking at a stagnant air mass

remaining in place through this weekend, so expansion of 

fog/stratus is possible. Current forecast is on track for today. 



&&



.AVIATION...Mainly VFR, areas of haze resulting in MVFR

visibilities in the lower Treasure Valley and near KMUO. 

Conditions improving to VFR through the morning. Surface winds: 

Variable up to 10 kt. Winds aloft at 10kft MSL: W-NW 10-20 kt. 



KBOI...VFR under thin high clouds. Surface winds: Light and 

variable, leaning NW after Tue/20z then leaning SE after

Wed/03z.



&&



.AIR STAGNATION...Current Air Stagnation Advisory has been 

extended until 5 AM MST Monday morning. The inversion will 

gradually weaken Saturday and Sunday, and a cold front Monday 

should be strong enough to break the inversion and provide 

enough mixing wind to scour the stagnant air out of the valleys.



&&



.PREV DISCUSSION...

SHORT TERM...Today through Thursday night...Upper level ridge 

will reach maximum amplitude Wednesday directly over our CWA. 

It will easily be the strongest ridge in the middle latitudes 

anywhere in the northern hemisphere. This will cause abnormally

warm daytime temperatures above 5500 feet MSL, with an intense 

inversion below that will maintain air stagnation in the

valleys.  We expect fog and low clouds to slightly increase 

next two nights but hi-res models don't yet have it. The ridge 

will begin to break down Thursday as the axis shifts slightly

to our east. Higher elevations will cool slightly but the 

inversion will continue in the valleys.



LONG TERM...Friday through Tuesday...The upper ridge will 

continue to gradually break down and shift east this weekend, 

finally allowing our CWA to come under moistening southwest

flow aloft. On Monday a north Pacific cold front and supporting

upper trough will come inland with a 50-70 percent chance of 

rain and snow in our CWA (highest chance in northern areas), 

and just as important, mixing winds and a likely end to the 

inversion.



&&



.BOI WATCHES/WARNINGS/ADVISORIES...

ID...Air Stagnation Advisory until 5 AM MST Monday 

     IDZ012-014-016-033.

OR...Air Stagnation Advisory until 5 AM MST /4 AM PST/ Monday 

     ORZ062>064.



&&



$$



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DISCUSSION...DG

AVIATION.....NF

SHORT TERM...LC

LONG TERM....LC

AIR STAGNATION...LC