Ammon, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

046
FXUS65 KPIH 221940
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
1240 PM MST Mon Dec 22 2025

.KEY MESSAGES...

- High Avalanche Danger in the back country in the Upper Snake
  River highlands and in the back country of the Sawtooth
  mountains.

- Winter Weather Advisory continues until this evening for the
  Upper Snake River highlands, the Big Hole Mountains, and the
  Bear River Range.

- Very wet and warm storm expected to arrive afternoon on
  Christmas Eve and last into Christmas morning.

&&

.SHORT TERM /THROUGH CHRISTMAS DAY/...
Issued at 1212 PM MST Mon Dec 22 2025

A massive upper level low in the eastern Pacific will slowly
shift eastward over the next 36 hours. This puts the current
time in between storms, so as the current storm winds up in the
eastern zones tonight, Tue is a break from rain and high level
snow for most. But this break may at best last into the morning
of Christmas Eve. The low sets up close enough to the coast to
once again fling impulses of warm rain and high elevation snow
through CA, NV, and finally into the southern Gem State. The
exact timing of the worst rates of precipitation have a wide
spread among the various deterministic guidance, but the worst
generally will be the night time hours on Christmas Eve. So get
your travel done on the night of the 23rd or get going early
on the 24th. This low is so large that it has a massive fetch
from the south, so the air will be mild with temperatures
actually in a warming trend even with the return of clouds.
There is some let up Christmas afternoon, but that is relative
to the moderate to heavy precipitation the previous night.

Temperatures will peak Christmas Eve, with highs in the Snake
River plain in the lower to middle 50s, with places like
Stanley warming to around 40 to the middle 40s. For Christmas
Day, afternoon highs only drop about 1 deg F for most locations.
Cold air will wait for after this period.

Wind will stay in the breezy (10-20mph) to windy (20-30mph)
category the entire time. Expect southerly to westerly so
shouldn`t have an issue with any sort of flash freezing, and
nothing strong enough in this period to warrant an Advisory or
Warning.

&&

.LONG TERM /CHRISTMAS NIGHT THROUGH MONDAY/... Issued at 1212
PM MST Mon Dec 22 2025

The massive low along the west coast will begin to lift and move
inland early in this period. Warm moist air will continue to
generate rain and high elevation snow on Thu night/Fri/Fri
Night. The formerly closed low opens into a wave and all
clusters time the 500mb trough to pass through Idaho longitudes
on Sat afternoon. About 30 percent of the solutions have the
flow splitting and doing little to eastern Idaho, but the
remainder have the feature staying together and giving a final
round of rain and snow Sat/Sat night. Once this trough is pushed
eastward, a massive upper level ridge returns, shutting off the
precipitation, and allowing for larger temperatures spreads from
the morning low to the afternoon high, generally colder than it
has been, with lows and highs much closer to climatic normals
for the time of year; this means temperatures down 10 to 15
degrees for both highs and lows by Fri afternoon/Fri night. The
wind remains moderate to high, with the strongest wind Fri
afternoon through Sat, where Wind Advisory level strength is
possible.


&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1006 AM MST Mon Dec 22 2025

We still have plenty of moisture around, but there should be a
break for everyone as the main band of rain and snow lifts
northwest through tonight. BYI, PIH, and IDA are VFR and should
remain there even with precipitation still falling. Once the
band lifts north, we current have VFR conditions remaining in
place. One thing to watch will be with huge amount of low-level
moisture around, if forecasts are underestimating fog or low
cloud potential. Probability forecasts indicate there is a LOW
possibility, and right now it is too low to insert into any of
those TAFs. It does look like for DIJ we will see linger clouds
and MVFR conditions once the rain clears late this evening. For
SUN, they are finally seeing the prolonged period of low clouds
and precipitation ending...for now. We do have the potential for
more showers to impact the airport and indicated that with a
TEMPO group dropping things back to MVFR/IFR conditions. The
main band shifts north into the Wood River Valley this evening,
and we should see conditions returning to several hours of
MVFR/IFR weather. We do have them breaking out of that once
again, just before sunrise tomorrow. Again, something to watch
will be with huge amount of rain and snow that has fallen and
underestimating fog/low cloud potential due to lighter winds.

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM MST this evening for
IDZ060-064-066.

&&

$$

SHORT TERM...Messick
LONG TERM...Messick
AVIATION...Keyes