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000
FXUS65 KMSO 182040
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
240 PM MDT Sat May 18 2013

.DISCUSSION...Low level moisture from rain the last 24 hours
combined with an unstable atmosphere and surface heating is
producing numerous showers across much of the Northern Rockies
this afternoon. An isolated lightning strike or two are possible
with any shower this afternoon. Expect showers to persist through
the early evening hours with the exception of the continental
divide where showers will continue through Sunday morning. This
same scenario is expected Sunday.

Monday and Tuesday a weak ridge will nose its way into the region.
Sufficient low level moisture and heating will provide the
potential for showers in the afternoon again but be limited to
southwest Montana and along the divide.

Much warmer temperatures Monday and Tuesday will return with
highs in the mid to upper 70s. Enjoy the warm and relatively dry
weather Monday and Tuesday as the pattern will change by mid
week.

Few changes to the forecast for Wednesday and beyond. Confidence
remains high for a closed low to impact the northern Rockies
Wednesday afternoon or evening bringing scattered. A few may contain
heavy rain.

Thursday through Memorial weekend is expected to be much cooler
and wet. The closed low will move over the northern Rockies and
remain nearly stationary. Confidence is high for rain during this
time frame. Some areas could receive significant amounts but
confidence on the timing and location of heavier amounts are
uncertain at this time.

Small stream flooding in northwest Montana remains a potential
concern with heavy rain, however, the slower timing of the system
raises the potential for overnight snow. In this scenario, travel
over mountain passes would be difficult and heavy snow at times
would cause slush on the roads even at lower elevations.

&&

.AVIATION...Showers will continue to develop and increase in
coverage as the evening hours neat, then decrease in coverage after
sunset. There is a slight chance for thunderstorm development
later this afternoon that could impact all aviation sites. These
storms will likely be week and short lived. Visibility and
ceilings will drop with the showers and thunderstorms, as well as
obstructing mountain terrain. Showers will again linger around
western Montana and central Idaho for Sunday.

&&

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

$$

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