Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 151937

Area Forecast Discussion
National Weather Service Pocatello ID
1237 PM MST Thu Feb 15 2018


Updated afternoon forecast as it looks like the bulk of the wind
convergence zone snow has moved into the hills east of I 15. Looks
like the more significant impacts are finished for today.



.PREV DISCUSSION... /issued 335 AM MST Thu Feb 15 2018/

SHORT TERM...Today through Saturday. One of the main forecast
concerns today is snow across the eastern highlands and the
potential for snow associated with a possible convergence band
dropping through the Snake Plain. Most of the snow this morning is
in the eastern highlands with some pockets of light snow showing
up in the central mountains. There is some snow as of 3am along
that convergence area from Rexburg back toward Roberts. Otherwise,
not much going on with that FOR NOW. We should see snow across the
eastern highlands settling south through the day. That is where we
have some higher confidence with the forecast. Not so much with
the convergence band, simply because of the fickle nature of these
events and the models poorly handling them sometimes. This might
be one of those days. The data is persistent with redevelopment
with that band during the day as it drops south. It may take a few
hours to get that started but we will stick with the idea. We
painted a wide swatch across the Snake Plain anywhere from Mud
Lake to Driggs south to between American Falls and Craters to
cover this. In this area, we aren`t expecting a lot of snow but
it`s possible some quick accumulations could produce short-lived
travel issues. Across the eastern highlands from the Teton Valley
south to near Soda Springs, look for anywhere from a dusting to 2
inches. We could see some locally higher amounts but this the most
likely scenario. This would also be the most likely area to see
slick roads on occasion. Elsewhere, pockets of snow will produce
light accumulations mainly in the mountains. It`s been breezy in
places overnight and this will continue. That will create some
areas of blowing and drifting snow in the mountains but impacts
from this shouldn`t be huge and most likely in backcountry areas
and highest passes. By this evening, snow will be ending. It looks
like stratus should return across portions of the Snake Plain
tonight, but with gusty winds and the next storm already affecting
us...don`t look for any fog.

We go back to northwest flow through Saturday. That means
occasional snow once again for the mountains, mainly the Sawtooths
and higher elevations from Palisades to Island Park. It looks like
on Friday/Friday night, we should see some light snow extending
south toward Bear Lake and Soda Springs, but we will stress light
and may only be falling higher up. A bit of light snow is also
possible across the Plain but nothing to really write home about
it looks like. Saturday will actually snow ramping in the
afternoon especially in the mountains. This particular "wave"
might actually have a little more moisture for mountain snow. It
will be breezy each day which means there could be places where
blowing/drifting snow persists in the higher elevations
especially above pass level. Above average temperatures will also
remain, but that won`t last much longer. Keyes

LONG TERM...Saturday night through Thursday. Next significant
feature to impact the region arrives Saturday night, deepening
trough over western states into Monday. Models have come into better
agreement early in the period regarding the amplification of the
trough over Idaho. ECMWF still wants to try to briefly close the low
Sunday, but it does remain open and slowly progressive. Daytime
temps are warm enough Sunday to warrant a rain or rain/snow mix in
lower elevations, but cold front Sunday afternoon ends that threat
rapidly. Biggest impact will be the return to more seasonable
temperatures behind the cold front, with Tuesday appearing to be not
only the coldest day of the week but coldest that East Idaho has
seen since early in the season. Guidance continuing to trend
slightly downward, with lower elevation highs below freezing, and
some 15 degrees or so below normal - a significant change from the
season so far. East Idaho remains under the influence of trough
through the remainder of the period, and though the bulk of the
moisture shifts southeast of the state, there is enough uncertainty
to keep weak chances of additional snowfall focused over higher
elevations, and only slowly warming. DMH

AVIATION...Broad area of stratus now in place over the Snake Plain
with a few lingering showers over the northeast corner, mainly
affecting KDIJ. There still appears to be the potential for
redevelopment of snow band similar to convergence zone early this
morning. This feature should primarily affect KIDA/KPIH through the
early afternoon with IFR ceilings/visibilities in SN. This band is
expected to shift south, clearing KIDA around 17Z, and KPIH around
20Z though a few high resolution model runs indicate that it could
stick around slightly longer than that for KPIH. There are differing
ideas on how much of the stratus should break up for the Snake Plain
zones. Will likely play the persistence card today and keep MVFR
ceilings in place where they currently exist. Otherwise, next
feature drops into place overnight, and will likely see potential
for at least VCSH return to KSUN in the 12z-18z time frame for Fri.



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