Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 062209
Area Forecast Discussion
National Weather Service Missoula MT
309 PM MST Thu Mar 6 2014
.DISCUSSION...Scattered rain showers will continue this afternoon
across the region. Heavier and more widespread rain is expected to
develop late tonight into the early morning Friday as another
surge of moisture moves east into our area. Clearwater and Idaho
counties in Idaho is expected to receive the most rain/snow
tonight, with the possibility of 0.50 to 1.00 inches rain. This
rainfall could increase the risk of rock and mudslides along the
more narrow and hilly roadways in the counties. Considering the
warm temperatures we had today and the additional rainfall,
flooding, particularly in the Bitterroot Valley, will continue if
not get worse. Aerial flood advisories will remain in place due to
the flood threat through at least Friday morning.
Elsewhere, moderate snowfall will create slick conditions over
mountain passes, such as Lookout, Lolo, Lost Trail, and Marias
through tomorrow morning. The heavier rain and snow should tapper
off tomorrow afternoon, though low land flooding will likely continue
into the weekend.
A ridge of high pressure will build over the western United States
Friday night resulting in warmer and notably drier weather on
Saturday. Clearing Friday night will likely yield some freezing
fog, which could be particularly thick at times given the over
abundance of ground water present across much of central Idaho and
western Montana. But this break in the weather will be short lived
as yet another push of warm Pacific moisture works its way into
the Northern Rockies. The snow level with this system will be
quite high, with rain falling up to between 6000 and 7000 feet by
Sunday morning when precipitation is forecast to be heaviest. All
model data suggests that winds at mountain top level will be
strong enough to yield downsloping in many of the north/south
oriented valleys and thus do not anticipate nearly as much total
precipitation falling in locations like the Missoula/Bitterroot
and Flathead/Mission Valleys Sunday morning. The chances for
heavier precipitation in the Missoula/Bitterroot are likely to
come late Sunday afternoon into Sunday night with a continued
moist but increasingly unstable atmosphere appearing to be in
place. This storm appears to be yet another verse in the ongoing
flooding concerns that the area is presently living and something
we will continue to monitor for specific impacts.
A cooler pattern will briefly exist over the Northern Rockies on
Monday and Tuesday, with rain and snow showers dwindling over the
region through Wednesday. Extended range models suggest that a
ridge of high pressure will re-develop over the region Thursday
through the following weekend, signaling a possible significant
warm-up. Forecast daytime temperatures are probably a bit
conservative and precipitation chances a bit aggressive
considering the model output. The trend to warmer weather will be
Scattered rain and snow showers over the Northern Rockies will
intensify later this evening through Friday afternoon. Airfields
across the region will experience temporary reductions in ceilings
and visibility at times. Terrain obscurations will be increasing
during this time as well. Fog and freezing fog will begin to creep
into the flying conditions for KGPI and KMSO by 08/0600Z.
.HYDROLOGY...Due to the rainfall overnight and the relatively warm
temperatures today creating additional runoff from snowmelt,
flooding concerns remain high, especially in the Bitterroot
Valley. Most of the lower elevations of western Montana and
central Idaho have the potential for flooded roadways, as well
as an increased danger of rock and mudslides through the night
into Friday morning.
Additional hydrologic concerns are again possible later this
weekend as a strong, warm feed of Pacific moisture returns to the
region. Additional overland flooding and rock/mud slides due to snow
melt and another round of precipitation are possible.
MT...WINTER WEATHER ADVISORY until 5 AM MST Friday for Lolo Pass and
Lost Trail Pass IN THE Bitterroot/Sapphire Mountains.
WINTER WEATHER ADVISORY until 5 AM MST Friday for I-90 Lookout
Pass to Haugan IN THE Lower Clark Fork Region.
WINTER WEATHER ADVISORY until 5 AM MST Friday ABOVE 5000 FEET
FOR THE West Glacier Region.
ID...WINTER WEATHER ADVISORY until 5 AM MST /4 AM PST/ Friday for
Lolo Pass and Lost Trail Pass IN THE Eastern Lemhi County...
Southern Clearwater Mountains.
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