Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Missoula Montana
231 PM MDT Sat Apr 19 2014

Discussion...a weak disturbance is still anticipated to swing
through the northern rockies tonight into Sunday morning. This
feature will bring scattered showers to the region, but impacts
will be fairly minimal. A brief ridge builds back over the area by
Sunday evening which will last into Monday causing a period of
warming and drying.

Tuesday-Thursday...the warm weather on Monday will come to an end as
a modestly strong surface low pressure system embedded in a broad
trough swings through the northern rockies starting Tuesday
afternoon. The relatively warmer air-mass ahead of the initial
push of energy and moisture will have the potential to produce a
few thunderstorms across central Idaho and southwestern Montana.

One of the main impacted regions will be central Idaho. Highway 12
in Idaho County could get a lot of rain in a very short period of
time with these showers and thunderstorms subsequently producing a
threat for rock and/or mudslides. Travelers and other personnel
should be extra vigilant Tuesday afternoon into the early morning
hours on Wednesday for the possibility of these hazards.

This system will quickly move to the northeast through western
Montana producing occasionally heavy rain in the valleys and a few
lightning strikes. The rain could produce ponding on roadways and
create a slight rises to the smaller creeks and streams. Some snow
could fall as low as the valley floor as the center moves over,
however snow isn't anticipated to be much of an impact given the
presence of warm subsurface temperatures. However mountains and
mountain passes, especially along the Continental Divide, could see
periods of heavy snow from Wednesday morning into Thursday.

Models continue to indicate that the surface low pressure will cut
off from the main flow and sit just east of the Continental Divide
wrapping a lot of moisture into the Glacier park region (including
marias pass). These locations are expected to be impacted the
greatest during this event due to the prolonged periods of rain
and snow. Snow could spread as far west as to Kalispell creating
slick conditions from Wednesday afternoon through the day Thursday.
Due to the heavy rain and Snow Rock and/or mudslides, as well as
avalanches could become an issue.

A weak ridge once again moves over the region on Thursday
decreasing chances for precipitation. But the models are indicating
a fairly steady stream of showers moving through the region Friday
into the weekend.


Aviation...a weak disturbance will move through the region
tonight causing a steady lowering of clouds and scattered showers.
These showers will obscure mountains and passes at times. The
shower activity is anticipated to diminish by late Sunday morning
into the afternoon.


Mso watches/warnings/advisories...


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