259
FXUS65 KPIH 041914
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
114 PM MDT Fri Sep 4 2026

.KEY MESSAGES...

- Showers and thunderstorms will persist across the central
  mountains through Saturday becoming more widespread Sunday and
  Labor Day

- Locally heavy rainfall is possibly later Sunday and Labor,
  potentially creating issues on/around steep slopes and burn
  scars

- Much cooler weather expected on Labor Day

&&

.DISCUSSION...
Issued at 1237 PM MDT Fri Sep 4 2026

We continue to watch the potential for showers and isolated
thunderstorms across the central mountains through Sunday
morning. There will be a potential for some locally heavier
rainfall, especially tonight. That said, a more prolonged and
widespread issue with heavy rain is not expected. We will let
the FLASH FLOOD WATCH for the Wapiti burn scar expire this
evening. Across the rest of eastern Idaho, the dry slot remains
in place along with gusty winds at times during the same period.
Gusts up to 30-35 mph are possible, especially at night where
downslope occurs or where areas remain above any weak inversion,
and during the afternoon with full mixing. Temperatures will
warm up a bit, with some low to mid 80s popping up across lowest
elevations.

The focus for the next chance of showers and storms
will occur later Sunday through Labor Day. The low that has
been sitting along the coast will swing across the state on
Monday. Ahead of that, we will pull in some monsoon moisture to
help fuel this round of showers and storms. It looks like at the
moment, any moisture from Marie will get pushed to our
southeast. We will likely get a small boost, especially closer
to the Wyoming border. Otherwise, rainfall will come from
whatever moisture is wrapping around the main low
itself...separate from the monsoon push. The best chance of rain
will be Sunday night and Labor Day, with a very strong dry slot
wrapping back into eastern Idaho later in the day. Rainfall
amounts across the Snake Plain, Magic Valley, and South
Hills/Albion Mountains will range from a few hundredths to close
to 0.25" north of Idaho Falls. Rainfall across the central
mountains should range from 0.10-0.30", EXCEPT across the higher
ranges (Sawtooths, Lost River, and Lemhi) where up 0.60" is
possible. Temperatures may be cold enough Monday, for a shorter
period of rain and snow across the higher peaks like Borah, etc.
For the eastern and southeast highlands, amounts currently fall
in the 0.20-0.50"...locally higher around Island Park where up
to 0.70" MIGHT fall. If we see heavier storms or multiple storms
over the same area, we could see some issue with localized
flooding in steeper slope areas and burn scars. It is possible
we may need to issue a FLASH FLOOD WATCH to later on to cover
the impacts. Winds will pick up on the back side of the low,
especially when the dry slot moves in. The strongest winds will
be across the Snake Plain north across the border into southwest
Montana. It is possible a WIND ADVISORY is needed for those
areas. We should fall short of any thresholds for a LAKE WIND
ADVISORY for American Falls Reservoir. Temperatures Sunday will
be similar to tomorrow, but much cooler Monday with lower
elevations highs MAYBE reaching 70. Mountain temperatures will
be in the 50s and low 60s, with highest elevations not getting
out of the 40s.

We get a brief break midweek, but southwest flow returns and we
see some monsoon moisture moving back into state after that.
Expect highs to return to the 70s and 80s and at least a low end
potential (for now) of showers and thunderstorms.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1118 AM MDT Fri Sep 4 2026

Very little change is expected with going forecasts. SUN remains
on the edge of upper low with continued threat of SHRA into this
evening, then a break is expected. All terminals remain VFR.
Winds decrease to light and variable into tonight, but there is
potential for PIH and IDA to see a brief return to breezy
10-15kt sustained winds after midnight.

&&

.FIRE WEATHER...
Issued at 1237 PM MDT Fri Sep 4 2026

Showers and isolated thunderstorms will remain confined to the
central mountains through Sunday morning. There is a low chance
of locally heavier rainfall mainly north of Stanley and across
the Frank Church. Otherwise, gusty winds will remain across the
rest of eastern Idaho through the same period. We will see
near-critical to locally critical fire weather conditions due to
the wind and afternoon humidity drop to near 15 percent. Through
this evening, this will be an issue across the southeast corner
(Zone 413), and tomorrow across Zones 410, 413, 427 and most of
Zone 425. We may also see this be an issue Sunday ahead of the
monsoon push across the Snake Plain (410) and most, if not all
of Zones 425 and 427.

Showers and thunderstorms will increase Sunday night and
continue through most of Labor Day, although this will quickly
shut off across the Snake Plain (410), Magic Valley and South
Hills/Albion Mountains (425 and 427) as a dry slot quickly wraps
back into eastern Idaho. It looks like the super majority of the
moisture from Marie stays to our southeast, with a very small
amount pulled into areas east of I-15. There is a separate
batch of moisture wrapping around the low itself that will be
the source of precipitation as the low crosses the central
mountains and Panhandle. For Zones 410, 425, and 427 look for
amounts from a few hundredths up to 0.25", highest across the
north end of Zone 410. Across the central mountains (422, 475,
and 476), amounts of 0.10-0.30" are possible, but closer to
0.60" across higher elevations north of Stanley and Zones
475/476. There even could be a rain/snow mix for peaks like Borah,
etc. For higher elevations east of I-15, look for 0.20-0.50"
EXCEPT around Island Park where up to 0.70" is possible. This
could cause some issues for any burn scars or steeper slope
areas.

&&

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

&&

$$

DISCUSSION...Keyes
AVIATION...DMH
FIRE WEATHER...Keyes