FXUS65 KMSO 191937
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
137 PM MDT Tue May 19 2026

.DISCUSSION...

KEY MESSAGES:

-  Scattered showers today with a few thunderstorms possible over
   the higher terrain. 

-  A system dropping into central Montana on Wednesday will push a
   boundary southward through western Montana driving thunderstorm
   activity through the afternoon and into the evening. 

-  Dry and increasingly warm conditions return later in the week,
   temperatures nearing 80 degrees(or warmer) by the weekend for 
   many locations.

-  Watching Monday for potential fire weather concerns in 
   southwest Montana ahead of the next system.

A west-northwesterly flow will promote scattered, disorganized
showers across the region through the rest of the day today.
Instability remains modest resulting in low (~10%) probabilities
for thunderstorm development except in the higher terrain (40%).
Precipitation amounts will remain light, generally under 0.15
inches for those that do see a shower. 

For Wednesday, an incoming closed low will track southward into
central Montana. The western edge of this low will enhance a due-
northerly flow across western Montana and push a boundary
southward through the region. Showers and thunderstorms will
organize along this feature with initiation in the Flathead Valley
around and after noon eventually reaching the Missoula/Bitterroot
valleys and points south closer to 5:00 pm and into the evening.
There is a 40% chance of lightning with these storms in any area
with shower/storm development along with the primary threats of
graupel, small hail, and erratic outflow winds of 25-35 mph. 

Behind Wednesday's system, high pressure builds across the
Northern Rockies, ushering in a quiet, dry, and warming trend to
end the workweek. By Saturday and Sunday, temperatures will peak
in the upper 70s and low 80s across most valley locations (warmer
in the lower river valleys of Idaho). Ensemble clusters suggest a
potential breakdown of this ridge by Monday. If this materializes,
the combination of a warm, dry weekend followed by increasing
pre-frontal winds could elevate fire weather concerns particularly
across southwest Montana.


&&

.AVIATION...A slightly unstable west-northwest flow will result in
scattered light showers and vicinity showers across most terminals
this afternoon and evening. Brief, localized reductions to MVFR
visibility and ceilings are possible under any passing showers
alongside mountain obscurations across the higher terrain. While
the probability of lightning is low today (around 10% for
valleys), it is non-zero. Otherwise, expect noticeably gusty
surface winds this afternoon with west-northwest gusts of 15-20 kt
subsiding after sunset.

&&

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

$$