736
FXUS65 KPIH 170349
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
949 PM MDT Sun Aug 16 2026

.KEY MESSAGES...

- Terrain-Driven Convection Today & Monday: An amplifying ridge
  removes large-scale forcing, but entrenched monsoonal
  moisture will support isolated-to-scattered afternoon
  thunderstorms over the mountains and highlands, producing
  localized gusty winds and brief heavy downpours.

- Enhanced Storm Potential Tuesday: A shortwave trough tracking
  through Montana across the top of the ridge will increase
  shower and thunderstorm coverage, primarily over northern and
  eastern high country.

- Late-Week Drying & Heat Surge: Northwesterly flow behind the
  departing shortwave will dry out the atmosphere for the second
  half of the week, with an amplifying ridge pushing lower-
  valley temperatures back into the 90s.

&&

.DISCUSSION...
Issued at 245 PM MDT Sun Aug 16 2026

An upper-level ridge of high pressure will build across eastern
Idaho today. While this building ridge will eliminate large-
scale upper-level support for organized convection, deep
monsoonal moisture remains firmly entrenched across the region.
Driven by diurnal surface heating, isolated to scattered
afternoon thunderstorms will develop primarily over the higher
terrain and mountain zones. High-resolution convective-allowing
models (CAMs) strongly support this terrain-driven convective
placement. The primary hazards with any developing cells will be
localized gusty outflow winds and brief, heavy downpours.
Convective activity will taper off quickly this evening with the
loss of solar heating, followed by a near-repeat setup on
Monday afternoon.

A shortwave trough is forecast to traverse the northern
perimeter of the ridge, moving across Montana from Monday night
through Tuesday. Associated height falls and glancing upper-
level energy will enhance shower and thunderstorm coverage
across eastern Idaho during this timeframe, particularly over
the Central Mountains, Continental Divide, and Eastern
Highlands.

Behind the departing shortwave, upper-level flow will shift to
the northwest as the ridge amplifies just to our west. This
northwesterly trajectory will shunt the primary monsoonal
moisture plume southward, pushing a drier air mass into the
Intermountain West and significantly reducing daily thunderstorm
chances for the second half of the week.

Daytime temperatures will steadily trend upward throughout the
7-day period. Expect afternoon highs to remain slightly below
seasonal normals through Tuesday before surging above average
Thursday through next weekend as the ridge axis locks over the
region. Lower-elevation valley locations, including the Snake
Plain and Magic Valley, will see a return to the 90s by late
week.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 942 PM MDT Sun Aug 16 2026

TSRA have finally ended in the past hour. The continued drying
out of the atmosphere will mean lower chances of TSRA activity
in the afternoon on Mon. At this time, it appears as though KSUN
will no longer be under a TS threat. KIDA appears to have little
threat of SHRA, so if any TS develop, expect dry TS. Deep
convection means outflow could be strong.

Outside of the TSRA risk, see no impact on airdrome operations
due to CIG, should be at 9,000ft AGL or higher, if any. There is
so little moisture, do not expect impact to VSBY even from TSRA.

Wind outside of TS should continue to be light, at 10KT or below,
with overnight conditions variable.

&&

.FIRE WEATHER...
Issued at 203 PM MDT Sun Aug 16 2026

A ridge of high pressure will continue building over the region
today, although monsoon moisture will be abundant enough to support
isolated to scattered convection the next couple afternoons.
High resolution models feature isolated convection this
afternoon across all Fire Weather Zones with isolated to
scattered thunderstorms across the mountainous zones, most
notably Fire Weather Zone 476. Thunderstorms will be capable of
heavy rain and wind gusts up to around 45 mph.

A shortwave feature passing to our north will flatten the ridge on
Monday before the ridge rebounds mid- to late week. This will mean
slightly cooler temperatures on Tuesday before we warm back to
around normal or slightly above normal later week. By next weekend,
ensembles show a deep PacNW low shifting the ridge eastward and
opening the door for the return of monsoon moisture.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...McKaughan
AVIATION...Messick
FIRE WEATHER...Cropp