Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 071110
Area Forecast Discussion
National Weather Service Missoula MT
410 AM MST Fri Mar 7 2014
.DISCUSSION...Light to moderate valley rain and mountain snow
showers will continue through this morning. The heaviest
precipitation will be mainly along the Idaho/Montana border into
north central Idaho and from the Mission mountains northward into
Glacier National Park. Mountain passes such as Lolo, Lost Trail
and Marias Pass all are snow covered and slick this morning and
thus winter weather advisories remain in effect. Temperatures have
lowered to near freezing in many valley locations, meaning that a
few patches of ice are possible on surfaces such as sidewalks and
secondary roads. Rain in the Missoula/Bitterroot and Mission
valleys should remain fairly light this morning however even light
amounts could increase the ongoing flooding in these areas. Numerous
flood advisories/warnings remain in effect.
The good news is that precipitation is expected to significantly
taper off this afternoon and evening as a ridge of high pressure
and drier air move into the region. Despite the end in
precipitation, lowland flooding due to snow melt will likely
continue due to the fact that temperatures will remain mild however.
There is a high likelihood of fog, dense at times, Saturday
morning due to clearing skies and lots of remnant moisture at the
Saturday night...With an increasing southerly wind gradient,
temperatures will stay milder. Places across southwest Montana
may be able to cool a little faster early on, but then plateau. A
plume of moisture moving around the upper level ridge will bring
precipitation mostly in the form of rain across northwest Montana
below 6,000 feet.
Sunday...The plume of above normal moisture will steadily push
southward during the day bringing a better chance for rain across the
remainder of western Montana. Snow levels will generally range
between 7,000 and 8,000 feet. Down-sloping effects will be felt with
strong westerly winds at ridge-top, lessening the amount of rain
that falls in the valleys. The Georgetown Lake area, I-90 corridor
between Drummond and Butte and the Camas Prairie in Idaho will
experience gusty southwest winds to 35 mph during the day. High
temperatures will be several degrees above normal. The warm
temperatures and high snow levels could potentially lead to
another round of increased snow melt/potential flood concerns and
increased avalanche danger.
Sunday night into Monday...A Pacific trough will move across the
region bringing another chance for precipitation. Snow levels will
gradually fall as this system moves eastward. There could be
a zone of heavy precipitation from north-central Idaho into southwest
Montana. A period of heavy wet snow is possible for Lost Trail Pass,
Georgetown Lake, Anaconda to Butte Monday morning. There also could
be a period of intense rain or rain/snow mixture across the
Bitterroot Valley which would hinder any flooding mitigation.
Forecast models are coming into better agreement on bringing a
ridge of high pressure back over the region Tuesday night into
Thursday, and possibly into the weekend. Have therefore decreased the
chance of precipitation for this time frame. Temperatures could
potentially reach to above normal for this time of year.
Scattered rain and snow showers over the Northern Rockies will
continue through this morning, but should begin to decrease in
coverage this afternoon. Airfields across the region will
experience temporary reductions in ceilings and visibility at
times. Terrain obscurations will be widespread during this time as well.
Fog and freezing fog will also be a possibility this morning for
KGPI and KMSO. Ceilings and visibility will begin to improve this
evening however there is a high potential for widespread valley
fog and low stratus to develop by Saturday morning.
MT...WINTER WEATHER ADVISORY until 11 AM MST this morning for Lolo
Pass and Lost Trail Pass IN THE Bitterroot/Sapphire
WINTER WEATHER ADVISORY until 11 AM MST this morning ABOVE 5000
FEET FOR THE West Glacier Region.
ID...WINTER WEATHER ADVISORY until 11 AM MST /10 AM PST/ this morning
for Lolo Pass and Lost Trail Pass IN THE Eastern Lemhi
County...Southern Clearwater Mountains.
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