Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 092054
Area Forecast Discussion
National Weather Service Missoula MT
254 PM MDT Sun Mar 9 2014
...Flooding potential continues as more rain is on the way...
.DISCUSSION...Not much has changed with the overall forecast
reasoning given the continued high degree of consistency within
numerical weather models. The first round of very heavy rain has
made its way through the region and has resulted in steady rises
to small streams and creeks across parts of NW Montana. Additional
flooding issues are likely to arise as this heavy rain continues
to drain off the mountains and into the lower elevation streams.
But the good news is that the focus of heaviest precipitation will
steadily be shifting south over central Idaho and parts of west
central into southwest Montana overnight as a second weather
system and cold front approach.
This second precipitation maximum is already starting to produce
more robust precipitation over Clearwater & Idaho counties as well
as over the higher terrain of far southern Ravalli and northern
Lemhi County. All the data supports continued enhancement of
rainfall and heavy higher terrain snow tonight which by Monday
morning will likely produce some significant flooding impacts. But
just where these impacts will occur still remains a bit
uncertainty as it largely depends on variables such as remaining
lower elevation snow, ground saturation and current creek/stream
levels. We believe all these factors will ultimately play into the
flooding picture and thus have continued the Flood Watch for those
areas of chief concern. Those who live within this watch and near
areas which could flood are encouraged to keep watch tonight
through tomorrow and have an plan in place should flooding occur.
Accompanying this second wave of precipitation will be an
increasing threat for snow impacts. The heaviest amounts are
expected over the higher terrain over Lost Trail Pass through
Georgetown Lake tonight. However additional accumulation down to
around 5000 feet are expected by Monday morning, which should
even affect the city of Butte with several slushy inches for the
morning commute. The atmosphere will turn quite unstable during
the afternoon with additional snow accumulations possible but
being quite variable and continue through Tuesday morning.
The rest of the week appears to be largely quiet with high
pressure becoming dominant. Cool nights followed by seasonable
warm days appear likely. There is low confidence with a weak
system breaking through the ridge on Friday.
.AVIATION...Few aviation impacts are expected at the larger
airfields of KMSO, KGPI and KSMN through the next 24 hours.
Widespread low clouds may obscure terrain...especially overnight
as precipitation intensifies over central Idaho and southwest
Montana. KBTM and throughout southwest Montana will see mixed
precipitation transition to snow early Monday morning with a
problematic period due to snow and low visibilities and ceilings
likely through Monday night.
MT...WINTER WEATHER ADVISORY from 6 AM Monday to 9 AM MDT Tuesday
ABOVE 5000 FEET FOR THE Butte/Blackfoot Region.
ID...WINTER WEATHER ADVISORY until 6 AM MDT Tuesday for Lost Trail
Pass IN THE Eastern Lemhi County.
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