Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 232027
Area Forecast Discussion
National Weather Service Missoula MT
227 PM MDT Wed Apr 23 2014
.DISCUSSION...Very unstable conditions have led to numerous rain
and snow showers across north-central Idaho into western Montana
this afternoon. There was a report of snow mixed with graupel in
Columbia Falls earlier, so graupel couldn`t be ruled out. Lookout
Pass has been receiving snow showers all day, but road surfaces
are warm so the only impact would be periodic reductions in
visibility and slush. An influx of slightly stronger winds in the
mid-level region of the atmosphere will move through southwest
Montana this afternoon and early evening. This will bring the
potential for gusty winds between 30 to 40 mph especially along
the I-90 corridor from Garrison Junction to Butte, along State
Highway 141 north of Avon and at MacDonald Pass on US-2. Have
introduced the chance for patchy fog in a few valleys of northwest
Montana. There could be just enough thinning of the clouds to
allow for some fog or stratus to develop, but confidence is low.
An upper level ridge moves through Thursday morning, but will not
bring quiet weather. There will be an above normal chance for
precipitation due to an influx of Pacific moisture moving through
this ridge. The best timing for widespread rainfall across central
Idaho will be Thursday morning as the leading upper level wave
moves through. Continued showers are expected through much of
Thursday. A possible break in precipitation across northwest
Montana will be possible by Thursday night ahead of the next
weather system. Have lowered the chance for precipitation there,
but have continued higher precipitation chances across central
Idaho. Normal high temperatures this time of year across western
Montana range from the mid-50`s to the lower 60`s. Missoula and
Kalispell are around 60 degrees while Butte is around 55 degrees.
Thursday highs will come in just under those readings.
Another trough will pass through the region Friday through the
weekend. There are similarities between the upcoming weather
system and the one that recently passed with moisture to arrive
from the south and cold fronts to bring wind and lower snow
levels. Multiple shortwaves within the main trough will again
create chances for mountain pass snow and periods of slick
conditions across Lemhi County and along the Continental Divide
Friday night and on Saturday night.
There are still indications that high pressure will begin to
develop early next week and last into midweek. Uncertainties
remain on the placement and strength of the upper level ridge but
a warming trend with decreased chances for precipitation is
looking more likely.
.AVIATION...Rain and snow showers will continue through this
afternoon. Gusty winds will also remain in association with a
passing shortwave. Brief reductions in visibilities and ceilings
are possible under stronger showers especially at KGPI and KBTM.
Showers and wind will decrease this evening as a weak ridge
moves into the region. North central Idaho will have little if any
break in cloud cover and rain as the next warm front moves over tonight.
Western Montana on the other hand may have isolated areas of
clearing that in conjuncture with afternoon showers will lead to a
chance for fog Thursday morning. Any patchy fog that does develop
will be short-lived. Showers and cloud cover will increase from
the southwest on Thursday with the passage of the warm front.
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