Libby, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

154
FXUS65 KMSO 310800
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
200 AM MDT Thu Jul 31 2025

.DISCUSSION...

KEY MESSAGES:

- The KMSX Radar (Missoula, MT local weather radar) will remain
  offline due to scheduled maintenance through the first week of
  August.

- Flash Flood Watch in effect for this afternoon and evening for
  Lemhi and Idaho counties in Idaho and Ravalli County in
  Montana.

- Widespread shower and thunderstorm activity continues Friday
  into Saturday, focusing across northwest Montana.


High pressure building east of the Continental Divide and a trough
of low pressure over the northern Pacific will keep an easterly
pressure gradient over the Northern Rockies today. Easterly winds
this morning will increase late this afternoon over northwest
Montana. The Pacific low will also result in southwesterly flow
aloft transporting moisture into north-central Idaho and western
Montana this afternoon. Anomalously high precipitable water on the
order of 200% of normal will arrive in Idaho and Lemhi counties,
as well as west-central Montana, by this evening. Clear skies in
the morning will mean ample low-level heating and an unstable
environment for the moisture plume to interact with. Lack of much
shear to speak of and weak upper level steering winds will keep
the primary threat from afternoon and evening thunderstorms as
heavy rain and frequent lightning. A Flash Flood Watch will be in
effect for Lemhi, Idaho, and Ravalli counties. Flood prone areas
remain the primary concern, including recent burn scars and areas
of steep, rocky terrain such as the Salmon River corridor and US
Highway 95 north of Riggins. Instability will be significant
enough to warrant chances for isolated strong to marginally severe
thunderstorms producing strong winds to about 40-50 mph.

The focus of shower and thunderstorm activity will move north of
I-90 Friday into Saturday as an upper level low slowly spins
towards the USA-Canada border. Thunderstorms will once again be
capable of producing heavy rain, with Glacier Park standing out as
an area to be monitored closely in the coming days for any flash
flooding concerns.

A broad trough of low pressure will keep showers and thunderstorms
in the forecast through early next week. Cooler temperatures will
continue, with highs running 5-10F below normal.


&&

.AVIATION... Easterly or northeasterly winds will prevail
throughout the day today, becoming gusty in the evening at KGPI.
Thunderstorm activity will once again increase in the afternoon,
spreading from south to north. Gusty winds of 35-45 kts with
isolated 50 kt gusts, frequent lightning, and heavy rain will
accompany any storms that develop. Expect thunderstorm activity to
increase by around 31/2100Z at KSMN and KBTM. Storms should reach
KMSO by about 01/0000Z.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch from this afternoon through this evening for
     Bitterroot/Sapphire Mountains...Missoula/Bitterroot Valleys.

ID...Flood Watch from Thursday afternoon through Thursday evening for
     Lower Hells Canyon/Salmon River Region...
     Orofino/Grangeville Region...Southern Clearwater Mountains.

     Flood Watch from this afternoon through this evening for Eastern
     Lemhi County...Western Lemhi County.

&&

$$