Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 042132

Area Forecast Discussion
National Weather Service Missoula MT
332 PM MDT TUE AUG 4 2015

.DISCUSSION...Afternoon showers and thunderstorms will continue
to move through southern Idaho county, Lemhi County, and into
southwest Montana. These showers will come to an end early this
evening. The next disturbance will begin to move into north
central Idaho and west central Montana tonight. A few showers and
thunderstorms will pass overnight with best chances Wednesday
morning through north central Idaho and west central Montana.
Storm will then move into southwest Montana by early afternoon.
Drier air will move into northwest Montana, bringing dry and
breezy conditions on Wednesday. By Wednesday night, a trough will
approach northwest Montana, spreading a few overnight showers and
breezy winds over higher elevations.

A strong upper-level low pressure system will slide through
northwest Montana Thursday. Unfortunately, most of the
precipitation will remain north of the Canadian border, with only
a few scattered showers and afternoon thunderstorms on the Montana
side from around Polson northward. The main impact from this
system will be strong winds aloft which may be able to mix down to
the surface by the afternoon. Previous forecasts indicated the
system would pass by too early to maximize wind potential, but the
latest model runs are looking more favorable. These winds could
bring fire concerns to parts of central Idaho and west Central
Montana. The other change with this system will be much cooler
temperatures, especially over northwest Montana where highs may
struggle to climb much above 70.

A cool air mass and clearing skies moving in behind Thursday`s
trough will allow for good radiational cooling Thursday night,
which could bring a chilly morning across portions of western
Montana and central Idaho. High mountain valleys which are more
susceptible to cool nights such as Elk City ID and Polebridge MT
could see a frosty start to the day. As the day progresses, brief
ridging will bring a respite from precipitation chances across the
region, with sunny skies and slightly below-normal temperatures.

For the weekend and into early next week, forecast confidence is not
very high as forecast models have waffled lately with placement of
disturbances moving through. The general message is southwest flow
aloft with weak disturbances moving through the Northern Rockies at
times. With little confidence in any one period of time, we have
gone with climatology for the forecast, which translates to a
slight chance of showers/thunder in the valleys and a better
chance in the mountains (esp. over southwest Montana) with near-
normal temperatures.


.AVIATION....The afternoon will bring breezes in the 10 kt range
with occasional gusts to around 20 kts. Afternoon showers and
thunderstorms have developed, which will mainly impact KBTM, KSMN
and points between through early evening. Farther north and west,
isolated showers and thunderstorms will also pass through the
afternoon. Lightning and gusty winds will be the main concerns
with any storms that do form.



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