FXUS65 KMSO 091930

AFDMSO



Area Forecast Discussion

National Weather Service Missoula MT

130 PM MDT Fri May 9 2025



.DISCUSSION...



KEY MESSAGES:



-  Through Sunday: significant increase in area river/stream

   levels



-  Thunderstorms mainly Saturday and Sunday afternoons/evenings, 

   with a few strong to severe storms



-  Snow levels briefly down to 5000 feet early next week



Seasonally warm temperature through the coming weekend will push

area streams and rivers marginally higher, as high elevation

snowmelt briefly accelerates. There will be isolated locations 

approaching bankfull. Also noteworthy will be the temperature of 

water, which will be extremely cold and dangerous to wade into. An

extended cool pattern next week will allow water levels to 

modestly recede.



Westerly flow aloft will shift to southwesterly and intensify 

over the Northern Rockies between today and Saturday. Coincidental

with the southwesterly flow, thunderstorm potential will increase,

from widely scattered areal coverage late this afternoon/evening 

(mainly west central & southwest Montana), to a marginal chance 

of severe hail/wind for Saturday afternoon/evening. Generally, 

thunderstorms Saturday and Sunday will produce wind gusts in the 

40-50 mph range and brief, heavy rainfall.



A low pressure circulation anticipated to dig southward along the

US west coast will result in southerly flow over the Northern 

Rockies by Sunday afternoon. Model ensembles suggest that the

thunderstorm threat will shift to north central Idaho & 

northwest/west central Montana during this time. Prepare for at 

least small hail and wind gusts 40+ mph near any thunderstorm that

develops.



Global models and their ensembles suggest high certainty in a deep

trough of low pressure digging across the Western US during the

first half of next week. Mountain total precipitation 

accumulation up to 1.50", low elevation total precipitation up to

1.00", and snow levels briefly decreasing below 5000 feet will be

featured across the Northern Rockies during this time. Much of the

accumulating snowfall will be above area mountain passes, however

overnight periods will see rapidly changing conditions. 



&&



.AVIATION...



Westerly flow aloft will shift to southwesterly and intensify

slightly across the Northern Rockies air space through Saturday.

Less than 20 percent probability of thunderstorm for any given

location across southwest Montana, including KBTM, 09/2200Z

through 10/0200Z.



Thunderstorms will redevelop Saturday afternoon across Northern

Rockies air space, with probability above 50 percent for any 

given location across west central & southwest Montana (including

KBTM, KHRF, KMSO), with generally 20-40 percent probability of 

occurrence elsewhere in the region. Less than 10 percent 

probability of winds exceeding 50 kts and hail exceeding 1 inch 

across southwest Montana Saturday afternoon as well.



&&



.MSO WATCHES/WARNINGS/ADVISORIES...

MT...None.

ID...None.

&&



$$