Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
412 PM MST Sat Feb 20 2021

...Updated Aviation Discussion...

.SYNOPSIS...
Winds will become strong overnight into tomorrow for the Rocky
Mountain Front and much of north-central Montana, and breezes will
increase elsewhere. Periods of strong winds are expected at times
on Sunday and Monday over North Central and Central MT.
Temperatures warm to about 10 degrees above normal by Monday, but
cool off on Tuesday, as a front crosses the region and brings some
snow with it.

&&

.DISCUSSION...
This evening through Tuesday...
Periods of light snow will continue along the divide, but most of
the snow will fall above pass level, thus no significant impacts
expected today. Marias Pass is the only pass with significant
snowfall, and that is 3-5 inches over 30-36 hours, so not likely
to be worthy of an advisory. Otherwise, strong winds develop
tonight from west to east over North Central MT. The high wind
warning remains unchanged in area and time for now. It still looks
like the high winds should diminish below warning criteria Monday
evening as we lose the daytime mixing, but we will need to watch
for the potential need for extending the warning later depending
on how strong the front Monday evening/night ends up being.
Blowing snow will start to become less of an impact over the next
few days over the Plains as the snow compacts/melts and becomes
harder to blow around with the warmer temperatures. Afternoon
temperatures will continue the warming trend for tomorrow and
Monday, with widespread 40s at lower elevations and perhaps even a
few places reaching 50 degrees on Monday. Some heavy snowfall
could develop over the Rocky Mountain Front Monday and Monday
night with the approach and passage of a cold front bringing some
Pacific moisture, and a winter weather highlight might be needed
for at least Marias Pass, and perhaps a few other higher elevation
areas. Lighter snow is expected for much of the plains along or
behind the front, but amounts and impacts look on the low side for
now, so lower elevation highlights may not be needed. Expect
colder air and light snow to move back into the region, with
Tuesday highs currently forecast to be 10 to 15 degrees cooler
than Monday.

Tuesday night through Saturday...
Below normal temperatures are expected from Wednesday through
next Saturday, but extreme cold is not anticipated. We can expect
periods of light snow over the Rocky Mountain Front and mostly
Southwest MT, with the best chance currently appearing to be
Thursday afternoon through Friday night. Overall snow
accumulations look light at this time, but we'll have to see how
the expected timing and snowfall rates evolve as to whether any
advisories may be needed.

&&

.AVIATION...
412 PM MST Sat Feb 20 2021 (21/00Z TAF period)

Snow showers will move across southwest Montana through early this
evening, with the threat ending at KHLN by around 01z and at KBZN
and KEKS around 03z or 04z this evening. Brief reductions from VFR
to MVFR with mtn obscurations are possible as these showers move
through. LLWS will increasingly become an issue over north-central
and southwest MT later tonight into tomorrow, and strong winds will
also develop for KCTB tonight, and spread east across north-central
MT tomorrow.

Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  22  44  36  48 /   0   0   0  10
CTB  22  43  34  44 /   0   0  10  20
HLN  24  44  35  50 /  10   0  10  20
BZN  14  40  28  46 /  20   0   0  10
WYS   4  24  13  31 /  10  20  20  30
DLN  12  36  22  44 /   0   0   0  10
HVR  18  43  31  49 /   0   0   0  10
LWT  17  40  31  44 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 6 AM Sunday to 10 PM MST Monday Cascade...
Central and Southern Lewis and Clark...Chouteau...Eastern
Pondera...Eastern Teton...Judith Basin...Liberty...Toole.

High Wind Warning from 3 PM Sunday to 10 PM MST Monday Blaine...
Fergus...Hill...Meagher.

High Wind Warning from midnight tonight to 10 PM MST Monday
Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.

&&

http://www.weather.gov/greatfalls

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Special Weather Statement
National Weather Service Great Falls MT
535 PM MST Sat Feb 20 2021

MTZ052-053-210115-
Broadwater-Jefferson-
535 PM MST Sat Feb 20 2021

...A SNOW SQUALL WILL IMPACT NORTHWESTERN BROADWATER AND NORTHERN
JEFFERSON COUNTIES...

At 534 PM MST, a snow squall was located along a line extending from
near Helena to 6 miles northeast of Basin to 13 miles north of
Walkerville. Movement was southeast at 25 mph.

Winds in excess of 40 mph are possible with this squall.

Locations impacted include...
Boulder, Basin, Montana City, Wickes, Alhambra, Corbin, Clancy,
Jefferson City and Elkhorn State Park.

This includes Interstate 15 between mile markers 145 and 188.

Visibilities will drop quickly to less than a quarter of a mile in
this squall.

Use extra caution if you must travel into or through this dangerous
snow squall. Rapid changes in visibility and potentially slick roads
are likely to lead to accidents. Consider delaying travel until the
squall passes your location.

Conditions can deteriorate rapidly in winter weather situations. Be
prepared for snow or ice covered roads. Slow down and allow extra
time when traveling.

LAT...LON 4633 11254 4635 11249 4633 11246 4639 11240
      4643 11223 4646 11217 4650 11220 4652 11207
      4657 11202 4652 11175 4645 11169 4623 11185
      4608 11213 4625 11257
TIME...MOT...LOC 0034Z 298DEG 23KT 4657 11205 4636 11221 4623 11249

CMC