FXUS65 KBOI 192106

AFDBOI



Area Forecast Discussion

National Weather Service Boise ID

306 PM MDT Tue Aug 19 2025



.SHORT TERM...Tonight through Thursday night...An upper-level

ridge is building into the four corners region, and will

continue to develop over the next few days. Along with this, an

upper-level trough will be moving east along the southern

Canadian provinces, and combined, this pattern will lead to

southwesterly flow aloft. Weak shortwave troughing will move

across our northern zones Wednesday, which will keep

temperatures only near 5 degrees above normal. Hot, dry, and

breezy conditions will dominate through the period. Smoke from

nearby wildfires will continue to move into the region. Small

chance (<10%) of precipitaiton near the Western Magic Valley on

Wednesday and Thursday.



.LONG TERM...Friday through Tuesday...Ridge, monsoonal moisture, and 

thunderstorms...a combo for an active long term. An upper-level 

ridge over the four corners region will drift ever-so-slightly west, 

causing southerly flow aloft. This creates a myriad of effects, the 

most prevalent of which will be heat. Daily highs Fri-Mon will be 5-

15 degrees above normal, with Saturday looking to be the warmest, as 

well as have the least cooling relief overnight (Sat into Sun). 

Along with the heat, moisture will begin to stream in steadily with 

southerly flow aloft. PWAT values frosouth ofm the LREF has a 

vast increase of mid-level moisture occurring on Friday and 

Saturday, and lingering through the extended. The ensembles are 

currently showing values greater than 0.70" areawide Sunday, 

with lower elevation maxima getting over 0.90" PWAT at times. 

This would be very high PWATs for this time of year, with the 

75th percentile being 0.68", and the 90th percentile being 

0.82". What do all of these numbers mean? Well, afternoon 

precipitation chances rise from 15-20% Saturday over primarily 

the Southern Highlands to near 20%-50% Sunday, Monday, and 

Tuesday. Thunderstorm chances also look high during this period,

but there is too much uncertainty this far out with spatial 

coverage. Precipitation combined with high PWATs could lead to 

an elevated risk for localized flooding effects, especially 

Sunday-Tuesday. Otherwise, with the very warm and dry surface 

conditions, high bases should make winds the primary threat, but

also hint at a risk of dry thunderstorms. Fire weather risk 

will be elevated coming out of the warm and dry midweek into the

dry thunderstorm potential late this weekend. Smoke is expected

to continue from local fires.



&&



.AVIATION...VFR. Mostly clear skies. Low chance (<10%) of a stray 

shower/thunderstorm in northern Valley County. Local visibility 

reductions in the W-Central ID Mountains and Snake Plain near Mtn 

Home due to wildfire smoke. Surface winds: SW to NW 7-12 kts. Winds 

aloft at 10kft MSL: S to SW 5-15 kt.



KBOI...VFR. Smoke layers aloft. Surface winds: NW 5-15 kt this 

afternoon.





&&



.BOI WATCHES/WARNINGS/ADVISORIES...

ID...None.

OR...None.



&&



$$



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SHORT TERM...CH

LONG TERM....CH

AVIATION.....CH