St. Anthony, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

503
FXUS65 KPIH 220821
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
121 AM MST Sun Dec 22 2024

.SHORT TERM...Today and Monday. Multiple rounds of rain and snow
continue as we head into the holiday period. Lingering light
showers this morning will quickly move out of the eastern
highlands. We will get a quick shot of rain and snow later today,
mainly south and east of the 15/84/86 corridors. That quickly ends
this evening. The next round, which looks a bit more potent, moves
into the central mountains and Magic Valley after
midnight...spreading across the rest of eastern Idaho. That push
will end tomorrow evening, with lingering showers overnight into
early Christmas Eve morning. Snow levels remain at 5000-7000ft
through most of the period. We will actually see snow levels rise
across the Magic Valley, Lower Snake Plain and South Hills/Albion
Mountains to around 7500ft for a few hours Monday. By sunrise
Tuesday, look for snow levels to be at/near valley floors except
for the Magic Valley and South Hills where they remain near
5500-6000ft. Looking at liquid equivalent/rainfall numbers, most
areas will see around 0.10" at most. For the Sawtooths and
surrounding peaks, look for 0.20-0.50" with slightly amounts in a
few spots. Probability forecasts have a 30-50% chance of exceeding
that over a 36-48 hour period along the spine of the Sawtooths. For
the higher elevations of the South Hills, Albion Mountains, and
southeast highlands...we are expecting 0.30-0.80". There`s a
35-45% chance of exceeding that around Pomerelle and the Bear
River Range. For the lower elevations of the eastern highlands
looks for 0.25-0.50" with 0.75-1.00 for the Big Holes and the
Tetons. Some of these higher amounts may be inflated a bit by
showers vs widespread heavier precipitation. There is a 10-15%
chance of higher than 1" for the Tetons. Snow-wise, that equates
to the potential less than 1" for portions of the Upper Plain
where temperatures remain colder tomorrow morning. For the central
mountains, South Hills/Albion Mountains and southeast
highlands...we may crank out 2-6". Higher amounts pushing 10" is
possible across the spine of the Sawtooths and the Bear River
Range. There is a less than 20% chance for more in those areas. For
the Big Holes and areas adjacent to the Tetons, look for 6-12"
especially above pass level...and closer to 2ft potentially for
the Tetons. For now, the period of precipitation is long enough
that some impacts will be mitigated and we don`t think we will
need a WINTER WEATHER ADVISORY for portions of the eastern
highlands and Bear River Range. We will be close though AND will
likely see some slick spots at times especially for places like
Pine Creek Pass, Emigration Summit and Teton Pass. With the bulk
of heavier precipitation tomorrow, there is a bit more time to
mull the idea over. Keyes

.LONG TERM...Tuesday through next Sunday.
An active weather pattern is expected to continue through the
extended period as a favorable storm track from the Pacific will
support several H5 troughs moving into Idaho to finish out December.
The timing for these systems has remained consistent with previous
forecasts, centering around Tuesday (Christmas Eve) into Wednesday
(Christmas Day), Thursday into Friday morning, and finally Friday
through the weekend. The first two systems will remain fairly quick
moving in nature, supporting light precipitation totals of around
0.10-0.30" of QPF/rainfall in the valleys and 0.30-0.60" in the
mountains with each system, locally higher across our highest
elevations. Given W/SW flow, above normal temperatures with highs
mostly in the 30s/40s each day will support a mix of rain/snow
showers in the valleys and predominant snow in the mountains. With
respect to snow for each of these two systems, amounts are expected
to again remain light with the second system Thursday into Friday
morning coming in colder. Our latest forecast for Christmas Eve into
Christmas Day shows a T-2" in the valleys and 2-6" in the mountains
with that Thursday into Friday morning system supporting 1-4" in the
valleys and 3-8" in the mountains. Not seeing much support for
hitting any Winter Weather Advisory criteria for the Christmas
Eve/Day system but we may end up needing highlights for the Thursday
into Friday system dependent on future forecasts.

Following these two quick moving systems during the work week,
attention then turns to a more organized and slow moving atmospheric
river of moisture that is expected to move into Idaho Friday through
the weekend. This would help to support a several day stretch of a
rain/snow showers with W/SW moisture transport from the Pacific. The
latest GFS/ECMWF vertically integrated water vapor transport (IVT)
forecasts shows atmospheric river moisture moving into the Gem State
for the weekend which would help to keep our active weather pattern
going with daily rain/snow chances. Stay tuned as details on this
system late next week come into focus and plan ahead for possible
winter travel conditions at times next week as we keep with our
active weather pattern going for the time being. MacKay

&&

.AVIATION...Following an exiting shortwave trough into Montana early Sunday
morning, predominant VFR and dry conditions will continue ahead of
our next trough remaining on track to arrive throughout the day
today into Monday with another round of rain/snow showers. CIGS will
gradually lower associated with this incoming system with areas of
low stratus and or rain/snow showers leading to a mix of MVFR/IFR
CIGS/VIS at times, especially later in the day Sunday through Monday
morning. The most organized precipitation looks to move in overnight
tonight into Monday with progressively drier conditions building in
west to east throughout the day on Monday as a transitory ridge of
high pressure builds in from the west. MacKay

&&

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

$$