506
FXUS65 KPIH 152315
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
515 PM MDT Sat Aug 15 2026

.KEY MESSAGES...

- Lingering Burn Scar Flood Threat: Localized flash flood risks
  over the Wapiti Burn Scar will continue to decrease into the
  evening as monsoonal moisture exits, allowing the Flash Flood
  Watch to expire on schedule.

- Early-Week Passing Trough: A shortwave tracking north of the
  region Monday into Tuesday will bring 30%50% precipitation
  coverage to the Central Mountains, Montana Divide, and Eastern
  Highlands. The Snake Plain will remain predominantly dry.

- Late-Week Heat Surge: Strong Great Basin high-pressure
  ridging will rebuild mid-to-late week, restoring a dry, late-
  summer regime with valley highs returning to the 90s.

&&

.DISCUSSION...
Issued at 234 PM MDT Sat Aug 15 2026

An active start to the weekend continues across Eastern Idaho
as residual mid-level moisture fuels scattered afternoon showers
and thunderstorms. The primary operational focus remains on the
Wapiti Burn Scar; however, rainfall rates across the scar have
remained light to moderate thus far. As moisture transport
shifts eastward, the Flash Flood Watch for the Wapiti scar will
be allowed to expire later this evening. A noticeable drying
trend takes hold for the second half of the weekend. While high-
resolution convective-allowing models (CAMs) keep scattered
showers (3040% PoPs) focused over the Central Mountains on
Sunday, shower potential across the Snake Plain remains low-
confidence and highly isolated. Increased sunshine will allow
lower-elevation maximum temperatures to rebound back toward
seasonal benchmarks in the mid-to-upper 80s.

A quick-moving upper-level trough will track across the Pacific
Northwest into southern Canada Monday into Tuesday. While the
core dynamics of this feature remain well north of the Idaho
border, associated height falls and weak shortwave energy will
clip the northern tier of our forecast area. This will re-
introduce a 30% to 50% probability of showers and thunderstorms
across the Central Mountains, the Montana Divide, and into the
Eastern Highlands. Given the drier low-level air mass in place,
storms in these zones will be capable of gusty outflow winds
alongside localized brief downpours. Further south across the
Snake Plain and Magic Valley, precipitation chances drop below
15%.

Behind the departing northern disturbance, global model
ensembles display strong consensus in rebuilding a robust, high-
amplitude ridge of high pressure over the Great Basin. As 500mb
heights rise, a warm, dry continental air mass will lock into
place across the Intermountain West. This setup will effectively
shut off monsoonal moisture transport, returning Eastern Idaho
to a classic late-summer weather pattern. Expect widespread
sunshine, low relative humidity, and a substantial warming trend
through mid-to-late week. Afternoon temperatures will steadily
climb back into the 90s across valley locations, running 5 to 10
degrees above seasonal climate normals heading into next
weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 515 PM MDT Sat Aug 15 2026

Have extended TSRA activity into the late evening at KPIH, KIDA,
KBYI, and KSUN. KDIJ TSRA activity should go through the early
evening hours. All of them should wrap up by 16/06Z. The
monsoonal push is ending on Sun, with considerably less
available moisture. However, the daily heating should trigger
more vigorous TSRA than Sat. The start of TSRA also seems to be
later in time, closer to 16/20Z and going later.

With the drier atmosphere, the three lower elevation airdromes,
KPIH, KIDA, and KBYI, have no expectations of SHRA, so have
included only TS in this case, indicating dry TS. Much harder to
impact surface VSBY, so do not expect any impact to VSBY at
those airports on Sun afternoon and evening.

CIGs should be limited to direct hits from a TS; even with this,
CIGs will have no impact on airport operations as they should
stay at 7000ft AGL or higher.

Wind outside of TS activity, should not exceed 10KT.

&&

.FIRE WEATHER...
Issued at 137 PM MDT Sat Aug 15 2026

Main impact next several days will be shower and thunderstorms
development. This afternoon and evening will be most widespread
with gusty outflow winds possible but also localized wetting
rains. Coverage much less widespread Sunday and Monday but
still at least isolated coverage is expected. Hotter and drier
conditions to return Wednesday into next weekend with nothing
more than isolated mainly mountain convection.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...

&&

$$

DISCUSSION...McKaughan
AVIATION...GK/Messick
FIRE WEATHER...GK