Area Forecast Discussion
Issued by NWS Missoula, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
FXUS65 KMSO 292138

Area Forecast Discussion
National Weather Service Missoula MT
238 PM MST SUN NOV 29 2015

.DISCUSSION...A ridge of high pressure continues over the Northern
Rockies causing strong valley inversions. Northwest Montana and
portions of north central Idaho will be affected by low clouds,
patchy fog and occasional flurries for a few more days. The
Missoula and Seeley Lake valleys will experience stratus clouds to
develop each morning and potentially burn off during the
afternoon. Areas under the low clouds will have fairly small
minimum to maximum temperature changes. While areas clear of the
low clouds will experience temperatures swings of 20 to 30
degrees. These strong inversions are also causing a decrease in
air quality each day. These conditions are anticipated to linger
into Tuesday.

For Wednesday into Thursday a weak disturbance will knock the
ridge of high pressure down. This feature will help break up a few
valley inversions, but the majority should remain intact. This
feature appears to cause some light precipitation, especially across
northwest Montana and north central Idaho. The potential exists
for the development of pockets of freezing rain during this time
frame, which could cause changeable and possibly very slick road

By Friday, an approaching trough of low pressure will further help
to stir up lingering cold pools in the valleys. This should help
improve air quality and bring warmer temperatures to currently
frigid valleys. More widespread precipitation is possible with
this system, especially for the higher terrain which could lead to
a period of snow over mountain passes.


.AVIATION...Very strong surface high pressure, due to cold air
trapped in valleys, continues to be a big weather player in the
Pacific northwest. Currently, satellite loops and surface
observations show low stratus and fog in western Idaho and west
central/northwest Montana. Some of the low level cloud cover has
recently dissipated around the Missoula Valley and near
Grangeville, so further improvements are likely during the
afternoon before stratus returns late this evening. Most of
northwest Montana remains firmly under the low cloud shield so any
improvements will be short-lived, if at all. Light snow will be
possible out of the stratus tonight and Monday morning. With
little change in the weather pattern expected through Monday,
conditions in the region should remain very similar to today.



$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.