Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

000 
FXUS65 KMSO 180930
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
330 AM MDT Wed Oct 18 2017

.DISCUSSION...
The strong winds that brought havoc over western Montana 
yesterday have generally subsided overnight, though some gusty 
winds still remain over the terrain and Continental Divide this 
morning. Breezy winds are forecast to continue today, peaking in 
the afternoon and evening hours. However, winds are not expected 
to be nearly as strong as yesterday. High temperatures will be 
slightly cooler due to less wind and a cooler air mass in place.

The next feature will bring rain and high elevation snow (above
5500-6500 feet) to northwest Montana beginning this afternoon and
persisting through Thursday. Strong west-southwest flow aloft will
keep precipitation mainly over the terrain during this period. As
the flow turns more southerly on Thursday, breezy winds combined
with warm flow will allow temperatures to reach well above normal
once again.

By late Thursday evening, a strong cold front will begin pushing
into central Idaho/northwest Montana, and continue eastward
reaching the Divide by mid morning on Friday. The front itself
will bring a quick burst of precipitation to most areas, followed
by showery weather the remainder of Friday into early Saturday 
morning. Snow levels will be quite high ahead of the front but 
will drop to mountain pass levels behind it, thus occasional snow 
covered roadways above 5,000 feet could be an impact as early as
sunrise Friday. Also, Friday daytime highs will be 15-20 degrees 
cooler compared to Thursday along with breezy westerly wind, so 
plan accordingly for the cool/showery conditions.

A very wet and mild westerly jet stream will be focused on the
Northern Rockies Saturday night through early Monday. Ample
precipitation (several inches of moisture) is likely across north-
central Idaho and the terrain of northwest Montana, along with
windy conditions on the terrain. The Camas Prairie region of Idaho 
will also see windy conditions on Saturday. The valleys of western
Montana will have breezy winds and will likely experience 
rainfall but much less compared to the higher terrain because of 
downsloping. Initially, snow levels may be at mountain pass levels
but will quickly rise to above 6500 feet for much of the event, 
limiting road impacts. But those in the backcountry should prepare
for frequent wet and raw conditions including the potential for 
accumulating snowfall above 6500 feet.


&&

.AVIATION...Winds have decreased this morning for TAF sites, but 
remain gusty over mountain tops and the Continental Divide today. 
TAF sites are likely to see wind gusts of 20-25 kts generally 
after 18/2000Z, but not nearly as strong as yesterday. 
Precipitation will start moving into the terrain of northwest 
Montana by 18/2100Z and continue the next 24 hours. 

&&

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

National Weather Service Glossary of Abbreviations