Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 260946

Area Forecast Discussion
National Weather Service Missoula MT
346 AM MDT Wed Apr 26 2017

.DISCUSSION...The first wave of precipitation with today`s system has
already arrived over north central Idaho, and will continue to
move east this morning. Expect a wet and cool day, with abundant
cloud cover and rain below 5000 to 6000 ft. Temperatures today
and Thursday will run about 10 degrees below average as a trough
sets up over the Northern Rockies.

After today`s rain, a reinforcing shot of cooler air will move in
from the northwest, bringing snow showers during Thursday morning
for locations above 3000 to 3500 ft. Warm ground temperatures
will likely help in quickly melting snowfall, but mountain passes
such as Lookout, Lolo, Lost Trail, Marias, and Homestake will
likely see periods of snow-covered roads during showers. Even on
passes, amounts should be limited to a few slushy inches, but
travelers will still want to leave a little extra time to
navigate in the winter driving conditions. After daybreak
Thursday, daytime heating will make it even harder for snow to
stick. A repeat of this situation will occur Thursday night into
Friday morning, as showers continue and snow levels remain low in
the 3000 ft range.

During the afternoons on Thursday and Friday, valleys will have
high chances to see occasional rain & snow as showers drift
overhead, but precipitation will not be continuous. Cool and
mostly cloudy will be the trend, similar to most days the previous

A brief drier period is still in the forecast for Saturday; while
not a completely dry day, Saturday remains the day where there
will be the most breaks between showers. A trough passage on
Sunday has a fairly high potential to bring widespread
precipitation but the strength and amount of precipitation is
still in question.

The cool and showery pattern looks to remain for the beginning of
next week, but the aberrant ridge of high pressure may start
showing signs of building into the region around the middle of
next week.


.AVIATION...Radar currently shows rain spreading over the Northern
Rockies from the west. Periods of rain will last through a
majority of the day, with all terminals seeing nearly continuous
vicinity showers, along with off-and-on showers overhead.
Precipitation will be more spotty over southwest Montana and
Lemhi county, but even these drier locations will likely pick up a
few tenths of an inch of rain. Sites above 5000 ft like KBTM could
see precipitation fall as snow showers until noon. Isolated
thunderstorms are possible this afternoon with enhanced lift from
an incoming shortwave trough. Precipitation intensity and coverage
decreases after 27/0300z, but showers will remain into Thursday.



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