508
FXUS65 KPIH 222140
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
240 PM MST Sat Feb 22 2025

.SHORT TERM...Today through Sunday Night.
Midday satellite imagery shows a departing H5 shortwave trough
into Wyoming as a transitory H5 ridge of high pressure builds in
from Oregon. We did end up seeing some light reflectivity on radar
today, indicative of some light snow flurries in the mountains
but those have since departed with dry conditions expected
regionwide for the rest of the day. The influence of this ridge
overhead will be short-lived however as our first in a series of
Pacific troughs begins to move into the PacNW with widespread
rain/snow back across SE Idaho starting late tonight and
throughout the day on Sunday west to east. The latest GFS/ECMWF
IVT/IVW forecasts continue to support atmospheric river moisture
building in out of the SW from with this system with a focus
across WRN/CNTRL/NRN Idaho and higher elevations of the SRN/ERN
Highlands where SW upslope flow and orographic lift will support
more moderate to heavy precipitation accumulation. Elsewhere,
precipitation will still remain widespread but lighter in nature.
The main push of moisture will move in Sunday into Sunday night
ahead of precipitation becoming more isolated to scattered
heading into early Monday as best chances for precipitation shift
into SW upslope regions.

Precipitation totals Sunday through Sunday night have remained
consistent with previous forecasts with a widespread T-0.25"
everywhere outside SW upslope regions of the WRN/NRN CNTRL
Mountains and higher elevations of the SRN/ERN Highlands where
0.25-1.00" is expected. Locally higher totals will be possible in
the WRN CNTRL Mountains, especially up around the Sawtooth Valley
and west of Blaine/Custer Counties where 1.00-2.00" of
precipitation is expected. Snow levels with this system will start
around valley floors and climb to around 7000-8000 feet
throughout the day Sunday, supporting a mix of rain/snow or all
rain across our lower elevations with predominant snow above
7000-8000 feet. Highest snow totals are expected in the WRN CNTRL
Mountains and across highest elevations of the SRN/ERN Highlands.
Went ahead with a Winter Weather Advisory for the NRN Wood River
Valley and Sawtooth Valley region where 5-10 inches of snow is
expected above 7000 feet with 10-20 inches above pass level. Have
held off on any headlines for the Island Park/Big Holes area at
this time as snow totals look to remain in that 1-5" range with
5-10" across highest elevations along the Wyoming border region.

Winds have begun to increase out ahead of this system especially
in the higher terrain where wind gusts up to 61 mph so far have
been recorded in the Soldier Mountains north of the Camas Prairie.
Expect breezy winds at times into Sunday and Sunday night with
strongest winds in the mountains. Temperatures will continue on a
warming trend through the rest of the weekend with highs in the
30s/40s across lower elevations. Overnight lows will stay below
freezing tonight but will climb above freezing for most areas
starting Sunday night. As a result of these warmer temperatures
and precipitation, we will see increased snow melt across our lower
elevations heading into early next week. See our hydrology
discussion for more on that below. MacKay

.LONG TERM...Monday through next Saturday.
Series of fast moving shortwaves continue to impact the region
Monday and Tuesday. Precipitation associated with these features
generally impacts higher elevations. Temperatures are quite warm
on Monday with snow levels 6000-7000 ft, leaving potential for
rain in the lower elevations. Could see some lingering issues with
threat of minor lowland flooding due to snow melt and any
lingering rain on snow impacts. Highs cool off Tuesday and
Wednesday associated with the second feature bringing snow levels
closer to valley floors, through precipitation becomes much more
limited by that time. Flooding threat minimizes moving into mid
week as overnight temperatures drop below freezing once again. For
remainder of forecast period, ridge rebounds with dry conditions
expected through Friday. Temperatures warm again, and overnight
lows approach the freezing mark by Friday/Saturday once again for
Eastern Magic Valley and Raft River region. That could bring back
the threat of localized flooding by next weekend. Deterministic
ECMWF and GFS threaten another shortwave trough arriving over the
weekend, and ensembles are a little bit uncertain on timing. NBM
means shade potential as early as Saturday, but confidence is
better by the beginning of next week. DMH

&&

.AVIATION...18Z TAFS through 18Z Sunday.
VFR conditions expected to continue at all terminals through
about 06Z tonight with light winds below 10kts. Could see patchy
BR/FG around sunrise, with localized MVFR or IFR restrictions.
Next system begins to push into East Idaho after 06Z tonight, with
CIGS beginning to lower around/just after 12Z for KSUN. Should
see onset of precipitation spreading across the terminals 12-18Z,
mainly KBYI/KSUN. Have trended toward including VCSH for KPIH/KDIJ
VERY late in the period, but believe better chances exist for
those sites and KIDA after 18Z. DMH

&&

.HYDROLOGY...
Warm temperatures and incoming precipitation this weekend and
very next week will induce the potential for minor flooding across
some lower elevations in East Idaho. Most likely areas to be
impacted would be low elevations in the South Hills, Eastern Magic
Valley and Lower Snake River Plain where snow exists below 6000
ft elevation. Hazards could include elevated flows in small stream
channels and drainages, and ponding in flat areas and upstream of
plugged culverts or road berms. As a result, a Hydrological
Outlook has been issued for the eastern Magic Valley and lower
Snake River Plain south to the Idaho/Utah border where warming
temperatures and melting snow may lead to minor flooding impacts.
Localized lowland flooding may also occur outside of this area but
this product was focused on where temperatures will be warmest.
We will continue to evaluate over the coming days regarding any
changes to this product. Dallon/DMH

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 2 AM Sunday to 11 AM MST Monday for
IDZ072-073.

&&

$$