942
FXUS65 KPIH 120423
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1023 PM MDT Thu Sep 11 2025

.KEY MESSAGES...

- Cooling trend continues into the weekend.

- Isolated to scattered showers and thunderstorms continue today
  through the weekend.

- Next system may arrive as early as Sunday night or Monday.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 137 PM MDT Thu Sep 11 2025

Satellite imagery shows upper low centered over SE Oregon this
afternoon. Isolated showers and thunderstorms already developing
early this afternoon, mainly over higher elevation zones across the
central mountains and along the WY border, a couple hours earlier
than high-res consensus for today. Trend is to continue convection
across these areas, but also including the South Hills this
afternoon.  Main concern is for slower-moving and/or training storms
across the central mountains with potential to put down moderate to
locally heavy rainfall. This would be a bigger concern for recent
burn scars. As such, a Flash Flood Watch has been issued through 03Z
to cover the Wapiti burn scar in far western Custer County. HREF
continues to support high chances for thunderstorm development, with
high-end ensemble estimates supportive of 0.25-0.50" of 1-hr QPF.
Threat may be marginal based on burn scar guidelines, but recent
rainfall over the past few days and wet soil may lower those
thresholds. Elsewhere, storms have the potential to produce small
hail and gusts around 40 mph. Convective threat diminishes over the
evening. Upper low axis migrates east slightly for Friday.
Thunderstorm chances look similar to today, mainly isolated to
scattered over terrain zones OUTSIDE of the Snake Plain. QPF chances
look less favorable than today. Temperatures remain cool, with highs
generally in the 70s for Friday, even covering for ensemble spread.
Lows tonight and Friday night in the 40s, with a few low to mid 50s
along the interstate corridors and through the Raft River region.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 137 PM MDT Thu Sep 11 2025

No major changes in the beginning of the long term forecast, but we
DO have some changes to look at for early next week. More on that
in a few lines... For now, we will start with Saturday when an area
of low pressure is over the Idaho/Montana area and bringing some
more isolated to scattered showers and storms to the higher
elevations as this low begins to move out of our area. This won`t
bring a lot of precipitation to us on Saturday as the latest NBM
data shows only about a 10 to 20 percent chance of a tenth of an
inch of QPF throughout the day Saturday in the Southeastern
Highlands, South Hills, Central Mountains, and upper Snake River
Plain. Better chances for at least a tenth of an inch (think 20 to
40 percent chance) will exist throughout the Eastern Highlands and
up around the Island Park area. Highs on Saturday will be in the
upper 60s to mid 70s. Sunday will be a bit drier as a transient
ridge moves through during the day which will warm us up a few more
degrees by the afternoon.

Early next week another system heads our way. Yesterday, models were
quite divergent in how they handled it, but today they are coming
together a bit more. Now, the ECMWF shows a low developing in the
Pacific Northwest and moving into Central Idaho by Monday evening.
The GFS actually shows a similar solution and both models then drive
the low eastward into Wyoming. The ECMWF moves a bit faster than the
GFS on this movement, but for now it seems reasonable to keep shower
and thunderstorm chances in the forecast for at least Monday and
Tuesday. This increase in cloud cover and rain to start next week
will cool high temperatures down into the 60s to near 70 degrees for
the area for both Monday and Tuesday. High pressure begins to build
back in over the area on Wednesday as we warm up by about 5
degrees.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1021 PM MDT Thu Sep 11 2025

Will have VFR conditions through Friday evening. Afternoon winds
expected to be 10 knots or less up valley at all sites with
vicinity showers at DIJ and SUN. BYI, PIH and IDA should stay
out of any shower activity. There is a very low chance for
vicinity thunder at DIJ and SUN and kept out of the TAFs for
now.

&&

.FIRE WEATHER...
Issued at 137 PM MDT Thu Sep 11 2025

Deep upper low positioned over eastern Oregon this afternoon
gradually shifts east over Idaho through Saturday. Isolated to
scattered thunderstorms will remain forecast mainly each afternoon
and evening, and mainly over higher elevations. A few storms may
sneak into the Snake Plain but coverage expected to remain VERY
isolated at this time. Storms especially today will have the
potential to produce small hail and gusty winds around 40 mph. The
storms may be slow moving, so locally heavy rainfall will be
possible as well. Temperatures remain cool under the influence of
this deep low, helping to keep humidities above critical thresholds
through the weekend. Outside of thunderstorm gusts, winds remain
below critical thresholds as well. This upper low shifts east by
Sunday for a brief break in the wet pattern for most areas, but the
next system could arrive as soon as Sunday night.

&&

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

&&

$$

SHORT TERM...DMH
LONG TERM...AMM
AVIATION...GK
FIRE WEATHER...DMH