Ammon, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

096
FXUS65 KPIH 240553
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1053 PM MST Tue Dec 23 2025

.KEY MESSAGES...

- Rain and mountain rain and snow move in by Wednesday
  afternoon, continuing through at least Christmas afternoon.

- Lighter snow getting to lower elevations on Friday.

- A break in rain and snow on Sunday for your holiday return trip.

&&

.UPDATE...
Issued at 833 PM MST Tue Dec 23 2025

Cancelled the advisories for the Wood River Foothills, Lost
River Valleys, Challis/Pahsimeroi valleys, Beaverhead/Lemhi
Highands, and the Centennial mountains/Island Park region.
Though there is some snow in the forecast for these zones, most
all the snow is above 7000 to 7500 feet. There is no snow
forecast for Hailey, Arco, Challis, and Monida pass. Raynolds
pass and Targhee pass have less than 0.5 inch of snow
forecasted. There will be a lot of rain (1 to 2 inches for all
zones but Challis), but again the snow levels are currently too
high. If snow levels drop 500 to 1000 feet this will change. For
Friday morning, there is snow forecast in all these areas with
the next wave of moisture and much cooler temperatures expected.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 101 PM MST Tue Dec 23 2025

A quiet night tonight with cloud cover only, but on the morning
of Christmas Eve rain and snow start in the central Idaho
mountains. This will spread from a narrow band there by the
afternoon to every where in the forecast area. Moderate to heavy
rainfall will occur below 6000ft elevation. For the southern
tier of highlands, this will be nearly an all rain event with
some occasional light snow on the ridges of the Bear River
range. Hardest hit will be the Wood River and Big Lost basins.
However, the heavy snow will likely stay above 7000ft elevation,
with light snow lowering to near 6000ft elevation, so a Winter
Storm Warning has been issued for elevations above 7000ft. This
would include Galena Summit on the road between Stanley and
Ketchum. Elsewhere in the central Idaho mountains, the heavy
snow should stay above 7000ft or so, and the slightly lighter
amounts merit Winter Weather Advisories. The lower elevations
such as Challis and Arco have advisory thresholds of just 1 inch
or more accumulation, which will be just about what they will
reach in portions of the zones, but likely not Challis and Arco
themselves. In the Upper Snake River highlands, the snow level
should be quite high and limited to elevations above 7000ft,
which leaves just a locations near the Continental Divide
receiving the moderate snow.

It should be noted that the rain-snow line will shift greatly
during the event, and that forecast snowfall amounts could
suddenly become much larger or smaller with just a 500 foot
change in that rain-snow line elevation.

The rain and mountain rain and snow continues Christmas night
and Fri, but lesser accumulation rates. However, the snow level
drops to 4500ft to 5500ft elevation on Friday afternoon from
northwest to southeast, so snow may actually become a factor on
more roads even with lighter precipitation. More Winter Weather
Advisories may be needed to this Thu Night-Fri period. Much will
depend on how cold the incoming air is.

Temperatures continue mild, with lower elevations staying near
records on Christmas Eve, then a couple degrees of cooling on
Christmas, then temperatures in the 40s for most Snake River
plain locations on Fri and 30s in the populated areas in the
central Idaho mountains and eastern highlands.

Wind will be moderate to strong in the Snake River plain and
southern highlands starting Christmas Eve, but the Wind Advisory
level type of wind is limited to a few ridges in the southern
highlands. Wind subsides Christmas morning, but gets breezy in
the afternoon.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Issued at 101 PM MST Tue Dec 23 2025

The timing on the various clusters is excellent, with the only
differences on just where the open wave passes into the Great
Plains. One cluster of solutions has the wave splitting and the
colder windier northern portion moving through southern Canada;
that`s 21 percent of the solutions. The strong majority have the
northern part moving through on Sat, likely bringing colder air
and thus lower snow levels, though not as much moisture content
will be available. All clusters by Sun have high pressure
returning to the west coast. For Sun the forecast area stays on
the northwesterly flow side of the high, so temperatures will
reamain cool with it difficult to get really windy during the
time period, unless at ridgetop level. This upper level ridge
intensifies through next Tue, but the forecast area stays on the
colder side of the ridge. So temperatures should warm but be
slow to moderate as 2025 comes to a close. No precipitation
expected with the strong postive height anomalies expected from
Sun onwards.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1044 PM MST Tue Dec 23 2025

The next round of precipitation will reach central Idaho by mid to
late morning Wednesday, with onset of rain forecast at the terminals
between 18z and 21z. Models continue to advertise MVFR to LIFR CIGs
and VIS areawide Wednesday night into Thursday morning as organized
precipitation works eastward. More specifically, IFR/LIFR CIGs at
all terminals with the exception of MVFR at KBYI beginning around
03z Wednesday night. Given the consistency between model runs, have
leaned into this but not quite as pessimistic as some of the
guidance suggests.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 3 AM to 5 PM MST Wednesday for IDZ056-057.
Winter Weather Advisory from 5 AM Wednesday to 5 PM MST
Thursday for IDZ069-071-072.
Winter Storm Warning from 5 AM Wednesday to 5 PM MST Thursday
for IDZ073-074.

&&

$$

UPDATE...
SHORT TERM...Messick
LONG TERM...Messick
AVIATION...Cropp