Winter Storm in Idaho, March 1, 2018

Area Forecast Discussion
National Weather Service Missoula MT
211 PM MST Wed Feb 28 2018

.DISCUSSION...

Elevated light snow showers will exist over the Northern Rockies
through sunset this evening. Accumulations are anticipated to be
light and mostly confined to area mountain passes, with only minor
travel impacts due to snow covered roads. Clouds and warm air
aloft will keep most of the region relatively warm tonight.

The break in precipitation will be very short-lived, as weak
rain/snow showers develop across the Northern Rockies throughout
Thursday. Temperatures will warm significantly by Thursday
afternoon, resulting in appreciable low elevation snow melt. Some
low elevation locations, such as Hamilton, may exceed 45 degrees
by late Thursday afternoon.

Southwesterly flow will persist over the Northern Rockies Thursday
night into Friday. Multiple weak disturbance will traverse the
region in this flow pattern causing swaths of moderate to heavy
snowfall. The first disturbance will be draped over Lemhi county
Thursday night into Friday morning causing fairly steady snow in
the higher terrain with a rain/snow mix in the valleys. The
potential of moderate impacts is possible especially over Williams
Creek Summit and Lost Trail. Another potential impact for
Thursday night is a modified arctic airmass filtering into the
Glacier Park region. Temperatures will drop fairly quickly, but
the winds should not be as intense as other recent arctic
airmasses.

A more significant disturbance will sweep through the Northern
Rockies Friday into Friday evening. This feature might have enough
instability to cause a few lightning strikes over north central
Idaho. This band progresses into west central and northwest
Montana later Friday evening. Snow associated with this feature
could be fairly intense causing moderate to heavy snowfall.
Locations under this feature might receive a quick inch or two of
new snow. A concern will be the intense snow falling during the
evening commute and covering roadways suddenly across northwest
Montana.

The trough of low pressure settles over the Northern Rockies by
the weekend. This trough will keep showers lingering throughout
the region, especially during the afternoon and evening.
Temperatures appear to be hovering round 5 to 10 degrees below
normal by Sunday.

A broad, yet weak high pressure ridge is depicted over the western
US Monday through Wednesday, however there are plenty of embedded
weak storm systems around that will disrupt otherwise dry and
seasonally warm conditions. Over the Northern Rockies, plenty of
cloudiness, seasonal temperatures, and a slight chance of valley
rain/snow and mountain snow showers are possible. Minor travel
impacts due to snow on roadways may exist during overnight/early
morning hours, however they are anticipated to be short-lived.

&&

.AVIATION...High elevation snow will dwindle over the Northern
Rockies air space during the next 24 hours, with variable
cloudiness otherwise. The snow areas will obscure terrain at
times, particularly across northwest Montana. However, snow is
not anticipated to impact KGPI much during this time.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&