Scientific Forecaster Discussion
fxus65 kmso 121032
Area forecast discussion
National Weather Service Missoula Montana
332 am MST Tue Dec 12 2017
Discussion...high pressure remains in place, this means low
clouds (stratus), areas of freezing fog, and minimal diurnal
change in temperatures will continue to be common across many
valleys through much of this week. Occasional snow flurries are
also possible from the stratus, leading to a skiff of snow but
little impact. Mid-level moisture associated with a weak
disturbance will increase across the area Tuesday night into
Wednesday. This moisture may enhance snow flurries slightly and
help to lift fog into a stratus deck. Higher elevations will
continue to see mild temperatures for this time of year and mostly
sunny to partly cloudy skies.
The door opens to active weather beginning Friday afternoon/evening
as a cold front moves through the northern rockies. This system
has the potential to bring a period of accumulating snowfall to
the mountains and mountain passes of north-central Idaho and
northwest/west-central Montana late Friday through Saturday.
Depending on how quickly the cold air aloft moves through,
any precipitation for the valley will most likely fall as light
snow. There is much less confidence for freezing rain/drizzle to
occur with the initial introduction of valley precipitation on
Friday, but cannot be ruled out at this point.
A brief return to drier weather will return late Saturday before
the next system approaches on Sunday. Increasing westerly winds
are expected for the terrain, and another round of snow showers
are possible into early next week.
Aviation...abundant stratus and areas of freezing fog will be
common the next several days as strong valley inversions continue.
Kgpi, kmso and ksmn will experience low ceilings from stratus with
the lowest ceilings during the morning hours. Kmso will see
freezing fog at times particularly during the overnight and
morning periods. Occasional snow flurries will also be possible,
especially around kmso with only trace amounts expected.