726
FXUS65 KPIH 121732
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1132 AM MDT Fri Sep 12 2025

.KEY MESSAGES...

- Cooling trend continues into the weekend.

- Isolated to scattered showers and thunderstorms continue into
  the weekend.

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

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 229 AM MDT Fri Sep 12 2025

Radar this morning shows a few showers tracking northeastward out of
UT, clipping southeast ID and continuing into WY. Outside of just a
few nocturnal showers along the periphery of our CWA, conditions
will largely remain quiet ahead of activity this afternoon. Models
indicate the most probable timing of convective initiation this
afternoon will be around 3 PM, with activity expected to remain
outside of the Snake River Plain. The highest thunderstorm
probabilities are in the same regions as yesterday, across the
central mountains, South Hills, and a portion of the ID-WY border,
although probabilities are a bit lower today. Storms will be capable
of producing small hail and gusts to 35 mph, along with locally
moderate rainfall in the case of training storms. By 10 PM
tonight, most models indicate only a few lingering showers and
storms along our border with WY. Later into the overnight/early
morning hours, CAMs do show very isolated showers tracking
northward through the Snake River Plain. Daytime temperatures
today will run within a few degrees of yesterday`s highs,
running mid 70s in our valleys and 50s and 60s in the mid- to
high elevations.

&&

.LONG TERM /SUNDAY 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 /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1131 AM MDT Fri Sep 12 2025

Showers and storms this afternoon and evening will be a bit more
isolated than yesterday. Given the latest HI-RES models, will go
ahead and add a PROB30 for DIJ where the latest HREF 24-hour thunder
probability has increased to about a 40 to 50 percent chance. For
SUN and IDA, have VCSH in the TAFs due to low probability of
occurrence and high uncertainty. A few of the models show spotty
showers continuing into early Saturday morning. Outside of any
storms, expect VFR conditions to continue.

&&

.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...Cropp
LONG TERM...AMM
AVIATION...AMM
FIRE WEATHER...DMH