Winter Weather and Frost and Freeze in Idaho, May 16 to 19, 2026

Area Forecast Discussion
National Weather Service Missoula MT
122 AM MDT Sat May 16 2026

.DISCUSSION...

KEY MESSAGES:

- Unsettled, cool, and showery conditions persist into the
  weekend.

- Mountain snow this weekend will create difficult conditions for
  backcountry recreation, especially along the Continental
  Divide.

- Widespread frost and freezing temperatures are highly likely
  Sunday through Tuesday mornings.

At 1am, the snow level remains between 5500-6000 feet, we do
expect them to lower over the weekend eventually to 4000 feet or
lower. What does this mean, well the potential for a slushy
accumulation during hours of darkness at mountain pass level and
higher. Sun angles and lack of moderate precipitation intensities
will keep any impacts during the day to people ill- prepared for
cool and wet conditions. Those that are recreating in the
mountains should plan for cool and showery conditions, that can
produce hypothermia if lacking preparation. Showers will continue
through the weekend under cyclonic flow, mainly in the mountains
with light precipitation amounts, except along the ID/MT border,
Mission Mountains, and Glacier National Park Region where 0.50 to
1.00 inch of water equivalent is possible by Sunday evening. That
same time frame and those mountains ranges will also have the
potential for 4 to 12 inches of snow, mainly above 5000 feet.
Higher valleys of southwest MT could receive 1 to 5 inches of
snow, mainly tonight through Sunday morning.

Note: those forecast snow amounts are for a period of time longer
than our current winter weather advisories, hence the differences
in amounts.

By Monday, temperatures will be 5-10 degrees below normal for
this time of year. Kids will need jackets for the morning bus and
be carrying them home during the afternoon. Sensitive vegetation
will need care both Monday and Tuesday mornings, as temperatures
lower into the 20s in western Montana and higher valleys of north-
central ID. Cloud cover over the weekend, will likely keep
overnight lows above freezing below 4000 feet.

Tuesday through Friday will see a warming trend with dry
conditions. By Friday, temperatures could be 5-8 degrees warmer
than normal as a chance for showers returns.

&&

.AVIATION... Widespread showers have arrived, favoring KGPI,
KMSO, and KHRF. Expect widespread lowered ceilings down to about
2500 feet by Saturday morning, as well as continued precipitation
through about midday transitioning to scattered showers and
thunderstorms in the afternoon. Precipitation will obscure terrain
throughout the Northern Rockies airspace.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from midnight Saturday night to midnight
     MDT Sunday night for Bitterroot/Sapphire Mountains...
     Butte/Blackfoot Region...Potomac/Seeley Lake Region...West
     Glacier Region.

ID...None.
&&