Lake Wind Advisory 7, NWS Missoula, MT

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WWUS75 KMSO 110125
NPWMSO

URGENT - WEATHER MESSAGE
National Weather Service Missoula MT
725 PM MDT Sun Oct 10 2021

MTZ003-110230-
/O.EXP.KMSO.LW.Y.0007.000000T0000Z-211011T0100Z/
Flathead/Mission Valleys-
725 PM MDT Sun Oct 10 2021

...LAKE WIND ADVISORY HAS EXPIRED...

$$

Area Forecast Discussion...CORRECTED
National Weather Service Missoula MT
146 PM MDT Sat Oct 9 2021

.DISCUSSION...Today will be a relatively nice day, yet cool in
the breezes even in the sun.

Sunday our first system drops south out of Canada, this is a cold
system. A cold front associated with the long wave trough will
move through our area by mid-afternoon. There is jet energy
parallel to the front, so gusty southwesterly winds can be
expected, creating choppy conditions on area lakes, so please
plan accordingly. A few showers along the front, and developing
in unstable air behind the front, are the precipitation threats
through sunset. Locations with the highest probability of
measurable rain will be the Clearwater Mountains of Idaho and
along US-12 up to Lolo Pass.

After midnight Monday night, an area of snow showers develops in
Lemhi County, Idaho. For this reason we have issued a winter
weather advisory in Lemhi County. A mid-level low pressure system
will spin-up in the Idaho Falls area around mid-morning. Snow may
become moderate for a couple hours during the morning in southeast
portions of Lemhi County, specifically Gilmore Summit. Snow rates
one- half to an inch an hour will be possible.

During the afternoon Monday, the system will begin to move
northeast through the Yellowstone area. At this point, strong
moist northeast winds will develop over southwest and potentially
parts of west-central Montana. Some rain showers or rain-snow mix
showers may develop, with little to no valley accumulation
expected. After sunset, these showers are expected to continue for
Lemhi County in Idaho and portions of southwest Montana. A slushy
accumulation up to two inches is possible, especially at area
mountain passes, such as Homestake Pass.

Snow showers will likely continue along the Continental Divide
and into southwest Montana throughout Tuesday afternoon with an
easterly upslope wind.

So what have we not talked about yet? Remember we started this
discussion saying this is a cold system. Overnight lows will be
cold in many locations, especially those locations that see
clearing such as northwest Montana and Seeley Lake. By Wednesday
morning widespread teens are possible from Seeley Lake into
southwest Montana, and in the higher valleys of north- central
Idaho.

Overnight Wednesday the flow aloft changes to northwest, and a
wave of cold air slides down into north-central Idaho
destabilizing the atmosphere. This is a good pattern for snow
showers from Lookout Pass and along I-90, including the Clearwater
Mountains of Idaho. It is also a pattern that the models do not
forecast well, so we will continue to monitor the evolution of
this system.

&&

.AVIATION...High clouds will continue to increase across the
Northern Rockies today, and wind gusts of 15-20 kts will be
common into this evening. Clouds will lower with showers
increasing from west to east early Sunday morning ahead of a cold
front. Gusty winds of 25-35 knots will be common with and behind
the cold front on Sunday. Snow levels will also lower with
mountain snow by Sunday afternoon.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Lake Wind Advisory from 9 AM to 7 PM MDT Sunday for Flathead
     Lake in the Flathead/Mission Valleys.

ID...Winter Weather Advisory from 12 AM Monday to noon MDT
     Tuesday Eastern Lemhi County.

&&