American Falls, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

607
FXUS65 KPIH 210930
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
230 AM MST Thu Nov 21 2024

.SHORT TERM...Today through Sat night. Moderate to heavy snow
continues to be just a central Idaho mountain concern for the next
24 hours. Light snow is possible today and tonight in the ID-MT
border region, including Island Park and Spencer-Dubois areas.
Temperatures will warm enough today that afternoon snow
accumulation will appear smaller, with much of the snowing below
7500ft elevation changing over to rain. Snowfall tapers off late
tonight, mainly at elevations below 8000ft. Thus, the Winter Storm
Warning currently in effect will continue for the next 24 hours or
so.

Snowfall does continue to be light for Fri from morning through
Fri evening. It does not cease in the higher elevations, but the
accumulation rates are down. However, another embedded shortwave
in the southwesterly upper level flow moves through the forecast
area starting late Fri night. This time, there is more moisture
available for the Island Park Region, to where a Winter Weather
Advisory may be necessary for late Fri night through late Sat
night, and what looks very likely to be yet another Winter Storm
Warning for elevations above 7000ft-8000ft for the central Idaho
mountains. Some of the eastern highlands with the lower threshold
for Winter Weather Advisories may also qualify. The NBM guidance
was, for many locations, producing much more precipitation than
the operational/deterministic solutions. The only exception was
that the snowfall in the central Idaho mountains was actually much
less than those same solutions; thus boosted the QPF amounts
somewhat in the central Idaho mountains.

To avoid confusion, will allow this first event to end before
issuing for this second event.

The nearly continuous southwesterly upper level flow will mean
even if skies partially clear, there will be no bone-chilling cold
tonight, and Fri appears to be the warmest day of the week with
the short-lived break between storms allows skies to continue
clearing. The second storm will cool temperatures with the cloud
cover, but the mild subtropical air will still keep low elevation
temperatures getting to 40 deg F or warmer until the extended
period.

The snow storm on Sat does appear to pack some windy conditions
Sat afternoon into Sat night, so it does appear stronger than the
current storm in that realm. Messick

.LONG TERM...Sun through Thanksgiving evening. The pattern shifts
a little here as the coastal trough retrogrades westward and
allows the upper level ridge to sit over the northern Rockies.
This allows a dry Sun, but the storm track shifts farther south
and by Mon the rain and snow threat is not along the ID-UT border.
Both the southern and eastern highlands are all the focus of this
period, although admittedly not as much snow at the current and
next storm provide in the central Idaho mountains. With Idaho now
on the cold side of storms moving mainly through UT, temperatures
will stay mainly in the 20s and 30s, closer to climatic normals.
Thus the clouds and precipitation will continue, possibly breaking
out on Thanksgiving Day. Messick

&&

.AVIATION...An atmospheric river of moisture will continue to target
the Central Mountain region of Idaho with snow, rain, and lower
cigs. As such, periods of MVFR to IFR cigs/vsbys will continue
throughout much of the TAF period at KSUN...will review and refine
timing of greatest impacts in the upcoming 12z TAF package based
on the latest high-res guidance. Elsewhere, however, we continue
to expect only mid-level clouds and a few sprinkles will be able
to spill over into the Snake Plain and points east, resulting in
continued VFR conditions and only light winds at KBYI, KPIH, KIDA,
and KDIJ. Even though persistent radar returns have been observed
overnight into the KBYI area, none of this activity appears to be
reaching the ground or resulting in a significant drop in cigs,
likely due in part to strong temp/dew point depressions indicative
of a dry-leaning low- level airmass. Increasing aviation impacts
east of KSUN become much more likely by Saturday as a shortwave
trough ejects inland. 01

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 5 AM MST Friday for IDZ072>074.

&&

$$