052
FXUS65 KBOI 191125
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
525 AM MDT Sat Sep 19 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Rain showers in Idaho continue through the day, slowly moving
  eastward.

- Gradual warming and drying trend beginning Saturday and
  continuing through early next week.

&&

.SHORT TERM /Through Monday Night/...
Issued 237 AM MDT SAT SEP 19 2026
Behind an exiting low pressure system, moisture wrapping around
the center is streaming through Central and Southwestern Idaho.
The wrap-around moisture is supporting development of steady
stratiform rainfall in this region, clearly defined on satellite
and radar. Light rain in lower elevations and the Snake Plain
will taper off by this afternoon, with only a couple hundredths
of an inch of rainfall left out of this system. As the center of
the low moves east, wrap-around rainfall continues a bit longer
in Central Idaho higher terrain. Showers here will last through
the afternoon and early evening, with 0.05 to 0.2 inches of
rainfall possible by the time they move east. As the bulk of the
moisture has passed, these rainfall amounts don`t present much
of a flash flooding risk. Although, in very steep terrain soils
may be saturated and unstable, so a minor rockslide risk can`t
be ruled out. Behind the low instability is meager, but enough
for a 10% chance of lightning this afternoon in higher terrain.
Showers and clouds moving east Saturday night and wet surface
conditions will support fog/low cloud development through Sunday
morning in mountain valleys.

As the system departs Saturday evening, a ridge axis and rising
heights across the region support drier and warmer weather
heading into the coming week. Temperatures on Monday warm back
up to the low/mid 80s in lower elevations and mid 70s in high
elevation valleys. Skies are mostly clear and winds are lighter.

&&

.LONG TERM /Tuesday through Saturday/...
Issued 237 AM MDT SAT SEP 19 2026
A weak, broad low moving south of the region on Tuesday will
bring a 10-20% chance of showers and thunderstorms to South-
Central Idaho that evening. Overall synoptic flow over the
region doesn`t change too much though, with zonal flow to the
north shifting in and out but continuing a slight warming trend
through the week. The track of the weak low seems fairly
confident amongst models, although it is cut off from the
primary flow so some change is expected in future model runs.
The zonal flow moves firmly overhead Thursday night ahead of an
amplified trough off the West Coast. Chances for precipitation
remain <5% through Friday, before guidance consensus brings the
trough closer for more favorable moisture flux. Saturday
precipitation chances rise to around 10% across the area, with
temperatures cooling down beyond that.

&&

.AVIATION /12Z Saturday through Sunday/...
Issued 522 AM MDT SAT SEP 19 2026
Mainly VFR, with showers continuing over west-central ID
mountains and Magic Valley, before tapering off in the
afternoon. Patchy fog in mountain valleys this morning clearing
as the sun rises. Surface winds: NW-SW 5-10 kt, then NW-N 5-15
kt in the afternoon. Winds aloft at 10kft MSL: NW-NE 5-15 kt.

KBOI...Light rain showers in the vicinity early this morning,
then clearing late in the morning and early afternoon. Surface
winds: NW 5-15 kt.

Sunday Outlook...VFR conditions through Sunday with variable
winds less than 10 kt overnight and in high terrain and NW 5-15
kt in valleys during the afternoon.

&&

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

OR...None.

&&

$$

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AVIATION.....JM
SHORT TERM...JM
LONG TERM....JM