Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 012051
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
251 PM MDT MON SEP 1 2014

.DISCUSSION...The upper level flow over the next 24 hours will
shift from northwesterly to southwesterly in advance of a strong
upper level trough quickly approaching from the Gulf of Alaska.
This will result in another nice late summer day on Tuesday with
breezy winds and increasing afternoon clouds. A few late afternoon
showers may be possible along the International Border as the
system approaches.

Tuesday night a cold front will impact the northern Rockies.
Current model runs do not have a lot of overall moisture with the
system, but it is a very strong system. So even with somewhat
limited moisture available, model trends indicate it will be able
to produce a quarter to a half inch of rain over much of Northwest
Montana Tuesday night and Wednesday. Higher amounts are likely
over Glacier National Park and the Bob Marshal Wilderness. Most of
the precipitation will stay well north of Interstate 90. It is
also very likely that many high mountain locations will receive
some snow, but no passes are expected to be affected with snow
level above 7,000 ft at this time. Those planning to be in the
high country of Northwest Montana this weekend should be prepared
for ideal conditions for hypothermia with cool temperatures,
significant rain, breezy conditions, and the potential for mixed
precipitation.

Temperatures around 10 degrees below normal in the cold air mass
behind the front will bring the first widespread risk of frost to
much of Western Montana, including the Missoula, Bitterroot,
Mission, and Flathead valleys. Areas near Interstate 90 and south
of Interstate 90 in Western Montana are more at risk, whereas
locations farther north that get more rain will also likely have
more clouds preventing the frost. In any case, it will be a cold
morning for early September likely affecting sensitive plants left
exposed.

The exiting trough will leave northwest flow aloft in place across
the Northern Rockies into the weekend. Breezy afternoons and
temperatures running near normal are anticipated. Models are
showing yet another, perhaps stronger upper level trough dropping
out of Canada during the early to mid part of next week.
Confidence in this solution is better than normal a week out given
that little, if any, ridging is expected to develop over the next
week and a large scale trough is maintained across the country.
In fact, this trough could be the coldest yet! Stay tuned.

&&

.AVIATION...Breezy winds should be expected at KBTM, KMSO and
KGPI again tomorrow as the atmosphere destabilizes during the
afternoon. But overall pleasant late summer conditions are
anticipated at all air fields over the next 24 hours.

&&

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

$$



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