FXUS65 KBOI 081221
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
621 AM MDT Wed Jul 8 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Isolated to scattered thunderstorms this afternoon and evening
  across portions of southern Idaho. Storms may produce outflow
  wind gusts up to 40-60 mph, possibly moving through the 
  Treasure and Magic Valleys.

- Gusty winds late this afternoon and evening, with breezy
  conditions continuing each afternoon through the week.

- Hot temperatures continue, hottest Friday and Saturday.
 
- Shower and thunderstorm chances return early next week.

&&

.SHORT TERM /Through Friday Night/...
Issued 348 AM MDT WED JUL 8 2026
Moisture will linger over southwest Idaho today under
southwesterly flow aloft, bringing another round of isolated to
scattered afternoon and evening thunderstorms. Thunderstorms 
will develop along the higher terrain south of the Snake River 
in far southern Idaho and lift northeast. Storms are expected 
to weaken upon reaching the Snake Basin, but a few storms will 
persist as they enter the Magic Valley and southern Boise 
Mountains. Lightning and gusty winds 40-60 mph will be the 
primary hazards from storms, with localized blowing dust 
possible from outflows. Brief heavy rain is also possible in 
stronger storms. Thunderstorms should track to the east of the 
Boise Metro, but outflow gusts to 40 mph from distant storms are
possible.

Otherwise today, expect similar temperatures to yesterday with
highs in the mid to upper 90s in the lower elevations with 80s
to lower 90s in mountain valleys. Late this afternoon and
evening, northwest wind gusts 20-35 mph will develop in many
areas as an upper trough over British Columbia tracks east and
sends a weak, dry cold front through our area. Breezy conditions
with gusts 15-30 mph will continue into Thursday, strongest 
across southern Idaho. Breezy and dry conditions will result in
elevated fire weather conditions. Westerly flow aloft will push
moisture and the accompanying thunderstorm threat to our east.
High temperatures will cool by 3-5 degrees. On Friday, a strong
upper level ridge over the Desert Southwest will begin to build
north, bringing hotter temperatures. Lower valleys will reach 
the upper 90s to around 100 degrees. For Boise, there is around 
a 50-60% chance of reaching triple digits for the first time 
this season. Southwest flow aloft will bring breezy conditions 
to the higher terrain.

&&

.LONG TERM /Saturday through Wednesday/...
Issued 348 AM MDT WED JUL 8 2026
The center of a strong upper level ridge will move across the
Rocky Mountains and into the Northern Plains this weekend into
early next week. Temperatures will remain very hot on Saturday
with lower valley highs around 100 degrees. Temperatures should
cool a couple degrees for the rest of the period as the ridge 
axis moves east. However, a slight shift west of the ridge would
produce hotter temperatures. Expect locally breezy conditions 
each afternoon. 

Ensembles are in excellent agreement that monsoonal moisture
will work its way north around the ridge into our area early
next week. This will reintroduce the potential for showers and 
thunderstorms, especially across the higher terrain. An increase
of clouds and precipitation will also likely aid in the slight 
cooldown. Ensemble mean precipitable water values climb to 
150-200% of normal, or above the 90th percentile. Heavy rainfall
and flash flooding especially on recent burn scars could be a 
concern with deep moisture in place. Additionally, after a 
period of hot, dry conditions, lightning on dry fuels could be 
a concern for new fire starts, especially if significant 
rainfall ends up being more limited.

&&

.AVIATION /12Z Wednesday through Thursday/...
Issued 605 AM MDT WED JUL 8 2026
Mainly VFR. Isolated to scattered thunderstorms this afternoon 
and evening, mainly across far southwest and south-central 
Idaho, impacting the Magic Valley terminals. Storms capable of 
30-50 kt outflows, brief heavy rain, and blowing dust. Localized
terrain obscuration from wildfire smoke. High density altitude 
this week due to heat. Surface winds outside of storms: variable
less than 10 kt this morning, becoming W-NW 5-15 kt this 
afternoon. Gusts to 25 kt late afternoon and evening, except 
25-35 kt KBKE-KONO. Winds aloft at 10kft MSL: variable or SW-W 
5-15 kt.

KBOI...VFR. A 30% chance of shower/thunderstorm outflows (30-40
kt) reaching KBOI after Wed/23Z. Minor visibility reductions 
due to wildfire smoke this morning, with foothills obscured in 
smoke at times from fire activity. High density altitude this 
week due to heat. Surface winds: SE 5-10 kt this morning, 
becoming NW 8-13 kt with gusts to 20 kt by Wed/21Z. Winds aloft 
at 10kft MSL over KBOI: SW-W 10-15 kt.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning from 1 PM this afternoon to 8 PM MDT this 
     evening for IDZ423-426.
OR...None.

&&

$$

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AVIATION.....ST
SHORT TERM...ST
LONG TERM....ST