FXUS65 KMSO 221820
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1220 PM MDT Sat Aug 22 2026

.DISCUSSION...

KEY MESSAGES:

-  Strong thunderstorms today through the afternoon and evening. 
   Gusty outflow winds as the main threat. 

-  Cold front Sunday brings cooler temperatures but gusty westerly
   winds and dry air.

-  Ridge rebuilds early next week, warming and drying trend.

Partial clearing across southern and central Idaho has allowed 
for diurnal heating and weak instability by midday. Showers and 
thunderstorms are expected to increasingly initiate over higher 
terrain early this afternoon over Idaho and Lemhi counties and 
track northeastward. Multiple rounds of convection will persist 
through the evening, particularly across northwest Montana. The 
primary hazard will be gusty outflow winds of 35-45 mph, with a 
Marginal Risk (5% probability) for isolated severe gusts exceeding
58 mph. Frequent lightning (posing a threat for new fire starts) 
and small hail remain secondary concerns.

Precipitable water (PWAT) values near 1.0 inch, anomalously high 
for the region will yield a localized threat for excessive runoff 
and flash flooding over steep terrain, urban centers, and burn 
scars. Elevated instability will persist overnight across western 
Montana, maintaining the potential for isolated thunderstorms into
early Sunday morning.

A cold front will cross the Northern Rockies late tonight into 
Sunday, bringing brief thermal relief as daytime highs drop 10-15 
degrees to near seasonal averages. Deep boundary-layer mixing 
behind the front will combine with a dry post-frontal airmass to 
yield gusty westerly winds. Elevated fire weather conditions are 
expected across the region Sunday afternoon, potentially critical
for parts of southwest Montana.

Ridge rebuilding early next week will mark a return to hot and 
mostly dry conditions, though isolated afternoon thunderstorms 
remain possible in Lemhi County and southwestern Montana. By mid-
to-late next week, ensemble cluster analysis indicates 70% 
confidence in a return to a trough over the Pacific Northwest.
This pattern would support cooling with seasonable daytime 
temperatures, breezy afternoon winds, and scattered 
showers/thunderstorms (although not a particularly wet pattern). 

&&

.AVIATION...Partial clearing across southern and central Idaho 
will promote weak destabilization this afternoon, supporting 
scattered strong thunderstorms tracking southwest to northeast 
between 22/1900Z and 23/0400Z. Direct convective impacts will 
include erratic outflow gusts of 30-40 kt, small hail, and 
localized MVFR visibilities in brief heavy downpours. Low-level 
wind shear (LLWS) and localized turbulence are expected near storm
cores. Widespread VFR conditions will return post-frontal on 
Sunday, though deep boundary-layer mixing will yield gusty 
westerly surface wind gusts of 20-30 kt.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning from 5 PM this afternoon to 6 AM MDT Sunday for 
     Kootenai...West Lolo.

     Red Flag Warning from 1 PM to 8 PM MDT Sunday for Deerlodge/West 
     Beaverhead.

ID...None.
&&

$$