Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Missoula Montana
235 PM MST Thu Dec 12 2013
Discussion...a weakening weather disturbance will shift across
north central Idaho and western Montana later tonight and
Thursday. The air mass should remain cold enough to keep the
precipitation in the form of snow. However, amounts should be
quite light and less than a half an inch in valley locations for
the most part. Over the mountain passes (whitebird grade, Lolo
Pass, Lookout Pass, Marias Pass, etc), there could be 1 to 3
A rather moist and mild west to northwest flow should occur
Saturday into Monday. Temperatures should rise to above normal
values in most areas, with 40s in some valleys. The exception may be
Salmon where cold air could remain trapped. The warmer
temperatures may start breaking up ice in smaller streams. As this
ice begins shifting downstream, there is a relatively small
possibility of the ice become congested/jammed and some localized
low lying flooding. The streams, that we are aware of, that are
prone to these break up ice jam situations (but again, the
probability of a significant ice jam in any one stream is low) is
Lolo creek, rattlesnake creek, Flower creek (libby), Orofino
creek, and Warm Springs creek (anaconda).
The moist west to northwest flow should produce periods of light
precipitation...mainly in northwest Montana into Monday. The
precipitation should be in the form of light snow in the
mountains, but possible patchy freezing rain in the valleys in the
night and morning hours. Otherwise, generally dry conditions can
Longer term models continue to show a moist and colder pattern
possibly setting up toward the mid to end of next week. There is a
lot of model to model and run to computer run variation in the
forecast amount of cold and snow. So...at this point we are just
stating there is a possible change to a colder and moist pattern,
but confidence is low regarding how cold and how much snow.
Aviation...high clouds will gradually lower tonight as a weather
disturbance approaches northern Idaho and western Montana.
Scattered snow showers and increasing mountain obscuration can be
expected later tonight, especially northern Idaho and northwest
Montana. Kgpi and kmso appear the main aviation hubs that are
going to see some of the showers.
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