399
FXUS65 KPIH 031951
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
151 PM MDT Fri Oct 3 2025

.KEY MESSAGES...

- Cold front continues to shift east through tonight.

- Showers, storms, and much colder temperatures on tap for the
  weekend.


- Uncertainty headed into next week, but generally drier and
  slightly warmer into mid week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 151 PM MDT Fri Oct 3 2025

Elongated trough draped over Idaho into the Great Basin per
satellite imagery. Associated surface cold front draped across
central mountains with attendant precipitation band expected to
shift east through the remainder of today. Ample sunshine over
eastern half of the forecast area early today should be enough
to increase instability for mainly isolated thunderstorm
development through the evening. A few storms could become
strong with gusty winds and small hail, and portions of the
region remain under a MARGINAL RISK for severe this afternoon.
Upper low continues to shift east into Utah overnight, with
showers becoming more widespread across East Idaho overnight.
The showery nature leads to quite a bit of spread for rainfall
amounts through tonight, well described by previous discussion
as "feast or famine". Low-end 12-hr precipitation percentiles
6pm-6am range from next to nothing across the northwest portions
of the central mountains to just below 0.10" across the
southeast. High end ranges for the same time period approach
0.20" across portions of the central mountains to 0.50- 0.75"
across the southeast.

Precipitation chances do increase moving into Saturday as the low
shifts east into the Great Basin and showers become more widespread
especially for the Snake Plain and southern/eastern highlands. Like
tonight, precipitation amounts remain highly variable based on
shower coverage, but overall amounts do trend higher for areas
outside the central mountains. Cooler temperatures bring snow levels
down to around 9000 ft, allowing for light accumulations at ridge
top. Behind the cold front, temperatures cool into the 50s for most
lower elevation areas. Weak secondary shortwave drops through the
panhandle Saturday night, reinforcing shower development especially
across the southern/eastern highlands and adjoining areas of the
Snake Plain. Precipitation amounts begin to drop off through the
night. Overnight lows begin to cool but there is also quite a bit of
spread with the coldest probabilities approaching freeze for some
lower elevation areas. Model means keep temperatures elevated well
enough to preclude a potential headline for now.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 151 PM MDT Fri Oct 3 2025

Upper trough lingers across Idaho into early next week. Showers
linger Sunday along with temperatures remaining cool across the
region, followed by a drier and more northwesterly flow into Monday.
Precipitation chances begin to drop off early in the week, but this
is likely when we`ll have to more seriously talk about freeze
headlines. Model means for Sunday night bring widespread
frost/freeze concerns to most lower elevation areas. Model means
currently support a combination of a Frost Advisory for portions of
the Magic Valley and a Freeze Warning for most of the rest of the
Snake Plain growing areas, and low-end estimates would raise the
potential for this early season cold snap being the first hard
freeze. We`ll have a couple more days to hone this in, but those
with agricultural concerns remaining into the early part of next
week should keep an eye on the forecast. A brief upper ridge rides
over East Idaho for the middle part of the week, allowing daytime
temperatures to begin to trend upward, but overnight lows remain
cool. Another Pacific trough deepens off the coast, strengthening
the southwest flow across Idaho late in the week and gradually
increasing the precipitation chances through the end of the
week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1126 AM MDT Fri Oct 3 2025

Showers with some occasional thunderstorms are possible into
Saturday as low pressure crosses the state. The main issues will
be dealing with MVFR/IFR conditions, especially where heavier
precipitation occurs through the period. We have at a minimum
VCSH or -SHRA at all TAF sites throughout the forecast. We left
PROB30 in for afternoon/evening thunderstorms except at SUN. We
will need to monitor things and see what needs to be
changed/amended over the coming hours. There is a 10-30% chance
of gusts of 30kts or higher with convection at BYI, IDA, PIH and
DIJ. There is a VERY LOW chance we see gusts closer to 50kts
with storms farther east this afternoon and tonight.

&&

.FIRE WEATHER...
Issued at 151 PM MDT Fri Oct 3 2025

Showers with occasional thunderstorms will last through the
weekend. The larger area of precipitation in the central
mountains has broken apart as the closed low portion of the
split is developing across California and Nevada. The rest of
this event will be more showery or at least multiple bands of
rain and high mountain snow. The latest totals from now through
Sunday afternoon continue to be highest across the mountains and
highlands south and east of the Snake Plain. Amounts in the
central mountains are "lowest", with the official forecasts
ranging from 0.10-0.50". Looking at total ranges for up there,
drier spots may not even see 0.10", while the high end could be
closer to 0.50" in the valleys and 0.60-1.2" for the mountains.
For the Snake Plain and Magic Valley, anywhere from 0.10-0.60"
is forecast. The low end is from 0.10-0.33" and the highest
possible is around 1.0". For the rest of the highlands and
mountains, lower elevations should see 0.25-0.50" with higher
elevations closer to 1.0". The Bear River Range may be in the
1.0- 1.5" range. Some mountain ranges could see closer to 2"
worth of moisture. The trend is toward drier conditions for the
first half of the week. This is as a bigger area of low pressure
develops along the coast and we see stronger southwest flow.
This would warm us back up quite a bit. The question is when/how
much moisture from one or more tropical systems in the eastern
Pacific gets pulled north into Idaho later next week. Stay
tuned.

&&

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

&&

$$

SHORT TERM...DMH
LONG TERM...DMH
AVIATION...Keyes
FIRE WEATHER...Keyes