Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 091002
Area Forecast Discussion
National Weather Service Missoula MT
402 AM MDT Sun Mar 9 2014
...HEAVY RAIN TO BRING ADDITIONAL FLOODING CONCERNS ACROSS MUCH OF
WESTERN MONTANA & CENTRAL IDAHO THROUGH MONDAY...
...RAIN TO CHANGE TO SNOW ON MONDAY IN SOUTHWEST MONTANA...
.DISCUSSION...The very moist southwesterly flow with subtropical
origins currently moving through the region will continue to
bring light and moderate rain. Majority of the rain will be
focused in north central Idaho through northwest Montana, but the
focus will begin to move southward through today as the upper flow
becomes more westerly. The high amounts of rain and snow levels
around 7000 feet will lead to very high flood/mudslide/avalanche
concerns through much of the region.
The next system is still on track to bring between 0.75 and 1.50
inches of liquid from Idaho County to southwest Montana tonight
through Monday. As mentioned in the last discussion, precipitation
rates will be heavy at times in these areas. This would bring
additional water rises to streams, therefore increasing the flood
potential. There is a chance for rock slides and/or mudslides,
especially those areas that typically see them like the US-95
corridor south of Grangeville to Riggins. Another impact will be
10 to 14 inches of heavy wet snow in the higher elevations
including Lost Trail Pass and Georgetown Lake, while 3 to 5 inches
across the lower elevations including Philipsburg, Anaconda, Butte
to Homestake Pass seem reasonable. As the main upper trough moves
through Monday night, there will be snow showers around, some of
which could give additional snowfall.
After some lingering snow showers and below normal temperatures on
Tuesday high pressure will dominate the extended forecast into the
end of the week. Temperatures will warm to above normal after a cool
Wednesday morning. Model guidance do show a couple of shortwaves
to pass through the region, one on Thursday and another on
Saturday, so shower chances will increase.
.AVIATION...The first of two very moist weather systems is
currently spreading cloud cover and moderate to heavy rain through
north central Idaho and portions of northwest Montana. Rain will
continue through today and transition southward. Most airfields
will see little impacts to visibility with some lowering of clouds
as the heaviest areas of precipitation pass overhead. Many
locations have gusty southerly winds ahead of this moist weather
system that will continue through this morning. The trough
associated with this weather system will pass on Monday. KBTM and
throughout southwest Montana will see mixed precipitation transition
to snow early Monday with a problematic period due to snow and low
visibilities and ceilings through Monday night.
ID...WIND ADVISORY until 11 AM PDT this morning for the Camas
Prairie...Grangeville and Highway 95 IN THE Lower Hells
Canyon/Salmon River Region...Orofino/Grangeville Region.
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