868
FXUS65 KPIH 171852
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1252 PM MDT Thu Sep 17 2026

.KEY MESSAGES...

- Showers and thunderstorms continue through Saturday

- Hail and gusty winds are possible with storms through this
  evening, and locally heavy rainfall through Saturday

- Cooler temperatures are expected through Saturday before
  slowly warming up next week

&&

.DISCUSSION...
Issued at 1250 PM MDT Thu Sep 17 2026

Showers and thunderstorms have continued today as one
of more waves spin north across Idaho ahead of the low centered over
northern California. Showers and storms already this morning have
produced moderate to heavy rainfall, as moisture continues to become
deeper and more conducive for this to happen. For the rest of today
and into this evening, more showers and storms will
develop...especially where the dry slot behind this morning`s
precipitation has allowed for more sunshine to interact with the
humid airmass in place. Heavy rainfall at times is possible and will
be the main impact. Some stronger storms will produce hail and gusty
winds over 40 mph. The latter is already evident due to outflow from
storms over the eastern/southeast highlands, creating a slow moving
outflow boundary across the Snake Plain and into portions of the
Magic Valley. It is likely this boundary will become an additional
focus for storm development, in addition to anything from pure
heating. There is a MARGINAL RISK for severe storms across the area,
and certainly is possible with the conditions setting up.

The overall pattern remains unchanged through Saturday, as the
cutoff low over California is finally picked back up by the steering
flow across the rest of the western U.S. The low will still be a
slow mover, and finally shifts over the state on Saturday. Until
that low passes, expect multiple rounds of showers and storms
producing heavy rainfall at times. A combination of much higher
moisture content and more widespread showers and storms tomorrow
into Saturday, the potential for higher rainfall amounts has jumped
up quite a bit. Will everyone see the heaviest rainfall in the
forecast? No, but the potential is there and higher than the past
day or so. From the Wood River Valley south across the Magic Valley
and into the South Hills/Albion Mountains, potential rainfall
amounts through Saturday afternoon are the "lowest" and up to 0.35
is possible. Elsewhere, the potential is there from 0.50-1.0" with
locally higher amounts. The current storm total forecast is likely
showing the higher end of the forecast ranges, as likely not every
square mile shown in the gridded forecast is going to see those
amounts. We considered Flash Flood Watches especially in areas with
burn scars, but for now are opting to handle it on a case-by-case
basis in terms of any needed warnings.

Wraparound showers and storms are possible Sunday. Heading into next
week, there is a struggle on what happens with the next low moving
into the western U.S. Before it appeared the low would stay the
south and we would remain dry. There is some indication it may now
drift far enough north to bring some clouds and potentially more
showers and storms.  That seems to be handled by the Blend of Models
which does have isolated coverage daily across portions of central
and eastern Idaho. Temperatures will struggle to hit the 70s
tomorrow and Saturday, before warming back up early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1250 PM MDT Thu Sep 17 2026

VFR conditions expected outside of any showers and thunderstorms.
Slow moving low pressure system will keep clouds and precipitation
in place through the period. Best thunderstorm potential will
continue through the evening but even some nocturnal storms remain
possible overnight with storms appearing likely again for Friday
afternoon. PROB30s continue for this afternoon with gusty winds
possible in and around thunderstorm outflows but synoptic winds are
expected to remain generally light. CIGs should stay high enough to
remain VFR with BKN/OVC coverage but again some localized, brief
reductions will be possible with storms.

&&

.FIRE WEATHER...
Issued at 1250 PM MDT Thu Sep 17 2026

A low pressure system moving through the region will produce
intermittent showers and thunderstorms over the next 36-48 hours.
Ample wetting rainfall is expected especially across the central
mountains and eastern highlands, with lower totals in the Magic
Valley and south Hills areas. This system will depart over the
weekend allowing for drier weather to setup by the second half of
the weekend and into much of next week.

&&

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

&&

$$

DISCUSSION...Keyes
AVIATION...McKaughan
FIRE WEATHER...McKaughan