Kalispell, Montana Weather Forecast Discussion

786
FXUS65 KMSO 192030
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
230 PM MDT Fri Sep 19 2025
.DISCUSSION...
KEY MESSAGES:
-  Warm, sunny, dry conditions continue through Saturday (15
   degrees above average).
-  Westerly winds with gusts 30 to 40 mph Sunday could create
   hazardous, choppy conditions on area lakes, especially Flathead
   Lake where a wind advisory may be needed.
-  Low-lying areas could experience their first frost Tuesday
   morning.
-  Brief ridge builds early next week before a more unsettled
   pattern could return from Thursday onwards.
Main changes to the Sunday cold front scenario:
The cold front is a little slower to move across the region. It
could be more like mid-morning for north-central Idaho and mid to
late afternoon for west- central Montana, and into the evening
hours for southwest Montana. The extra cloud cover associated with
the front could prevent some areas across north- central Idaho
from experiencing widespread- stronger wind gusts. The latest NBM
shows 60 to 80 percent probability for gusts greater than 30 mph
primarily over western Montana, and higher than 90 percent over
the Divide.
With the slower frontal progression, the area for showers and
thunderstorms shifts slightly north towards Clearwater County in
Idaho and even as far north as Flathead Lake Sunday morning into
afternoon. Threats from the thunderstorms over Lemhi County
towards Butte include gusty winds to 45 mph, lightning, brief
heavy rain and small hail. There is a low chance for severe
thunderstorms as instability is low (200 to 400 J/kg MU CAPE) and
shear is around 25-30 knots.
Models are consolidating into agreement that the trough will not
be a typical west to east progression, but cutting off as it
tracks southeast over Wyoming by Monday morning. This means that
clearing may be slower Sunday night thereby reducing the chance
for colder temperatures by Monday morning. There could even be a
few showers overnight by Flathead Lake due to lake-induced
instability (albeit weak).
The probability for frost is generally 30 to 50 percent for some
of the low-lying areas across western Montana and higher valleys
of north-central Idaho on Tuesday morning.
A warm ridge is still on tap to build over the region Tuesday and
Wednesday. With the clear nights, patchy river fog is possible.
By Thursday and Friday the ridge starts to shift eastwards, but
it still continues to be warmer than average by 10 degrees. With
the region under southwest flow, that introduces the chance for
afternoon showers and thunderstorms towards the end of the week.
&&
.AVIATION...High pressure over the region will keep weather
impacts to aviation low today. Some patchy river fog may be seen
near terminals KMSO and KGPI, but it isn`t expected to spread into
either of the airports this morning. Winds begin to increase
Saturday afternoon with gusts up to 20 kts.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$

NWS MSO Office Area Forecast Discussion