Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 210947

Area Forecast Discussion
National Weather Service Missoula MT
347 AM MDT Mon Aug 21 2017

.DISCUSSION...With clear skies expected across all of western
Montana and north central Idaho, the only thing standing in the
way of having a perfect set-up for the eclipse is the amount of
wildfire smoke in valleys. Wind has all but died overnight for
most locations, allowing for smoke to settle back into valleys
across the region. This may cause a rather hazy appearance to the
skies for eclipse viewing purposes.

Smoke is expected to remain in most valleys going into Tuesday and
again Wednesday as conditions remain stable under strengthening
high pressure. This will result in a dramatic change come late
Wednesday through Thursday.

Forecast models remained in agreement overnight with a potentially
interesting day for Thursday. Scattered thunderstorms associated
with a strong cold front is still expected to move through the
Northern Rockies during the afternoon, that will have the
potential of producing strong gusty winds throughout western
Montana and portions of north-central Idaho. The difference with
this cold front compared with recent fronts, is how unstable and
convective it could be. Winds along the front, and with the
possible thunderstorms, will be capable of gusts up to 40 to 50
mph. The amount of available moisture with this system will bring
rain with what convection does develop. However, the speed at
which the thunderstorms will be moving will keep soaking rains
fairly isolated, as well as the thunderstorm coverage. With the
combination of all these factors, fire weather concerns will be
quite elevated, if not critical.

Friday will be a post-frontal day, so expect cooler than normal
conditions and lighter winds overall. No precip is expected right
now for Friday.

In fact, by Saturday, the Northern Rockies will return to a much
drier and much warmer (ie: well above normal) temperature pattern
through early to the middle of next week. In other words: no
relief in sight for ongoing wildfire suppression efforts. If
anything, smoke will be settling back into the region in earnest
under stable conditions.


.AVIATION...Stable conditions under strengthening high pressure
will occur today. Reduced visibility resulting from settling
wildfire smoke will impact KBTM and KMSO today into tonight, and
to a lesser extent KSMN and KGPI. Without much more than a light
afternoon/evening wind across the region, smoke will most likely
be the largest impact to aviation in the next 24 hours.



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