962
FXUS65 KPIH 212059
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
159 PM MST Fri Nov 21 2025

.KEY MESSAGES...

- Dense Fog Advisory from 11PM tonight to 10AM tomorrow morning
  for many.

- Remaining dry through the weekend before Monday cold front.

- Unsettled conditions may continue through the Thanksgiving holiday,
  but no significant impacts are expected at this time.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 155 PM MST Fri Nov 21 2025

Most of this morning`s fog has lifted enough to "just" be low
stratus now. While we are getting a little break this afternoon, it
looks to be pretty short-lived before the low stratus and fog return
tonight through early tomorrow morning. Given what we saw this
morning, we have decided to go ahead and issue a Dense Fog
Advisory for portions of the eastern Magic Valley, Arco desert
area, Snake River Plain, and Teton Valley from 11PM tonight to
10AM tomorrow. While some of these spots may not be at or below
1/4 mile visibility the whole time, models are showing about a
30 percent chance of VIS less than a half inch from Burley to
Rexburg with a 50 to 70 percent chance of the same from Shoshone
across the Arco desert up to Mud Lake. The HRRR, which handled
last night`s fog fairly well, does keep it a bit farther north
and out of Pocatello which may be due to it picking up on some
increased winds, but confidence in that is low enough to still
include these areas in the advisory. Either way, prepare to hit
some pockets of very low to near 0 visibility if you are
traveling late tonight into early tomorrow. Even a few areas
outside of the advisory area have about a 20 percent chance to
see visibility below a half mile in parts of the South Hills and
Southeastern Highlands.

The fog and stratus are holding our temperatures fairly steady
across much of Eastern Idaho today with temps this afternoon hanging
out right around 40 degrees or just on either side of it. By
Saturday afternoon, temperatures may warm just a couple of degrees,
but not by much. As temperatures fall into the 20s and 30s today
with more fog around, watch for some slick spots on roads and
especially on bridges or other elevated surfaces.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 155 PM MST Fri Nov 21 2025

The next shortwave feature arrives late Sunday through early
Tuesday, with cold front passage during the day Monday. Current NBM
means increase the winds along and behind the front to between 25
and 30 mph with gust potential over 40 mph. Light precipitation
appears mainly confined to higher elevations at this time. Cooler
temperatures follow Tuesday, with lower elevation highs dropping
into the 30s. For the holiday period, models are showing signs of
shifting gears again. Although the ensemble clusters agree on a
ridge through the western states, some of the deterministic runs are
a bit flatter with the flow aloft, leading to energy pushing through
the PacNW and producing light precipitation across the northern tier
states. Temperatures remain mostly mild, which would keep snow
generally above valley floors, and thus limiting impacts for holiday
travel concerns for Wednesday through Friday. At least for now.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1037 AM MST Fri Nov 21 2025

Areas of IFR or below fog and low stratus continue this morning
mainly through the Snake Plain and adjacent valleys, though DIJ
is maintaining VFR conditions just south of the cloud edge.
Although there is some potential for brief improvement this
afternoon and early evening for BYI/IDA/PIH, persistence will be
prudent path forward. There is a small chance (15-25%) of
seeing the moisture advect north during the afternoon and
evening for SUN once the diurnal winds shift to the south, but
the downslope flow onset after 02Z should clear that back out to
VFR. The rest of the terminals can expect some combination of
fog and/or low stratus to return to IFR or lower conditions for
the remainder of the terminal period.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 11 PM this evening to 10 AM MST
Saturday for IDZ051>055-065>067.

&&

$$

SHORT TERM...AMM
LONG TERM...DMH
AVIATION...DMH