Severe Thunderstorm Warning 3, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
334 PM MDT Tue Apr 30 2024

.SYNOPSIS...

A wintry spring storm brings periods of rain and snow to the area
through Friday morning. Temperatures cool to below normal values,
before warming, a bit, this weekend.

&&

.DISCUSSION...

Note: The forecast area for the National Weather Service Great
Falls Weather Forecast Office includes north central, central and
southwest Montana.

The next weather producer is upon us, offering below normal
temperatures and periods of rain/snow, into Friday. As of the
writing of this discussion, showery precipitation has begun, with
a few thunderstorms presenting across portions of the region.
Westerly winds flowing across The Northern Rocky Mountain Front
allow for some gusty winds to 40 mph. The Winter Storm Watch for
The Little Belt and Highwood Mountains has been upgraded to a
Winter Storm Warning. In this area, 7 to 13 inches of snow is
forecast at pass level. Please, see WATCHES/WARNINGS/ADVISORIES
section below for Winter Weather Highlights already in place.
- Fogleman

The larger scale closed upper level low moves east of the Rockies
tonight with its circulation shifting slowly across MT/AB/SK
through Thursday. Models are in general agreement and continue to
trend somewhat slower with the arrival of more widespread
precipitation circulating into the forecast area. Widespread
precipitation develops across southern AB/SK in association with a
TROWAL (trough of warm air aloft) and shifts southwest into areas
along the east side of Glacier NP by Wednesday morning. Colder
air aloft wraps into the circulation Wednesday with widespread
precipitation expanding south and east across much of north-
central MT by Wednesday afternoon with moist/cyclonic NW flow now
forecast to linger across the area through at least Thursday
afternoon. This has shifted the more impactful period of winter
precipitation for portions of central MT to late Wednesday through
Thursday, though precipitation amounts have not changed
significantly.

Winter storm warnings and advisories for The Glacier NP/Rocky Mtn
Front vicinity begin at midnight tonight with areas near the AB
border being initially impacted tonight before precipitation spreads
south on Wednesday. Winter weather advisories were added for the Big
Belt/Bridger and Snowy mountain ranges beginning Wednesday afternoon
with the Winter Storm Watch for the Little Belts continuing while
these highlights were extended through Thursday afternoon. There is
some potential for additional winter weather highlights across
portions of central MT adjacent to the Little Belts but considerable
uncertainty exists at these lower elevations due to marginal
temperatures with melting and compaction likely to limit
accumulation and impacts to roads. Still, the later onset of
precipitation towards Wednesday night and Thursday could allow for
some overnight accumulation and minor winter weather impacts to the
Thursday morning commute that will need to be watched.

Models continue to delay the exit of troughing from the area through
Friday though the bulk of the widespread precipitation should be
ending Thursday night. A brief period of ridging is possible early
this weekend before the next round of troughing arrives late this
weekend into early next week with models suggesting temperatures
remaining closer to seasonal averages for  this period. Hoenisch

&&

.AVIATION...
1152 AM MDT Wed Apr 30 2024 (30/18Z TAF Period)

VFR conditions prevail across all terminals during this TAF period.
However, snow at the KGTF, KBZN, KHVR, and KEKS terminals could
reduce ceilings to MVFR levels during the middle to end of this TAF
period. At the KCTB there will be light snow showers at the end of
this TAF period that should only have limited effects on aviation
operations. During the beginning of this TAF period there will be
isolated light snow showers at the KCTB, KEKS, and KCTB terminals
and so a TEMPO group was included for those TAFs. At the KHVR
terminal there will be isolated rain showers at the beginning of
this TAF period. There is a 20% chance for a rain/snow mix at the
KGTF and KHLN terminals at the beginning of this TAF period. There
will be gusty southwesterly winds (20 - 28 kts) at all terminals
during this TAF period. For the KEKS and KBZN terminals the wind
gusts will end by 03Z. During this TAF period there will be mountain
wave turbulence at times. During this TAF period there will be
intermittent mountain obscuration. -IG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  29  51  32  45 /  10  70  80  90
CTB  29  46  32  43 /  30  80  80  80
HLN  32  53  36  51 /  10  50  50  70
BZN  26  48  29  50 /  50  50  40  60
WYS  22  40  19  43 /  40  60  40  50
DLN  25  45  28  50 /  30  40  10  30
HVR  29  54  33  48 /  20  60  70  80
LWT  27  48  28  41 /  10  50  60  80

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from midnight tonight to noon MDT Thursday
for East Glacier Park Region.

Winter Weather Advisory from midnight tonight to noon MDT
Thursday for Northern High Plains-Southern Rocky Mountain Front.

Winter Storm Warning from 6 AM Wednesday to 6 PM MDT Thursday
for Little Belt and Highwood Mountains.

Winter Weather Advisory from noon Wednesday to 6 PM MDT Thursday
for Big Belt, Bridger and Castle Mountains-Snowy and Judith
Mountains.

&&

http://www.weather.gov/greatfalls

Special Weather Statement
National Weather Service Great Falls MT
222 PM MDT Tue Apr 30 2024

MTZ303-304-309-302100-
Eastern Pondera and Eastern Teton MT-Eastern Toole and Liberty MT-
Eastern Glacier, Western Toole, and Central Pondera MT-
222 PM MDT Tue Apr 30 2024

...AN INTENSE SNOW SHOWER WITH A THUNDERSTORM WILL IMPACT
NORTHEASTERN PONDERA...EAST CENTRAL GLACIER AND TOOLE COUNTIES
THROUGH 300 PM MDT...

At 218 PM MDT, Doppler radar was tracking an intense snow shower
with an associated thunderstorm near Cut Bank, moving southeast at
20 mph.

HAZARD...Wind gusts up to 50 mph. Heavy snow showers.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Visibility reduced to less than one half
         mile in snow and blowing snow will make for difficult
         driving along a portion of US Highway 2.

Locations impacted include...
Shelby, Cut Bank, Kevin, Ethridge, Oilmont, Santa Rita, Ferdig, and
Dunkirk.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Be prepared for difficult driving conditions in reduced visibility
and rapid slushy snow accumulation on roadways.

&&

LAT...LON 4865 11273 4897 11225 4866 11133 4817 11200
TIME...MOT...LOC 2018Z 300DEG 19KT 4867 11224

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

SC

Special Weather Statement
National Weather Service Great Falls MT
329 PM MDT Tue Apr 30 2024

MTZ301>305-307>309-302230-
Hill County MT-Eastern Pondera and Eastern Teton MT-
Southern Rocky Mountain Front MT-East Glacier Park Region MT-
Eastern Toole and Liberty MT-Southern High Plains MT-
Eastern Glacier, Western Toole, and Central Pondera MT-
Northern High Plains MT-
329 PM MDT Tue Apr 30 2024

...HEAVY SNOW SHOWERS WITH A GUST FRONT WILL IMPACT
PONDERA...CENTRAL LIBERTY...SOUTHEASTERN
GLACIER...TOOLE...NORTHWESTERN TETON AND WEST CENTRAL HILL COUNTIES
THROUGH 430 PM MDT...

At 326 PM MDT, Doppler radar was tracking heavy snow showers with a
gust front over Glacier, Toole, and Pondera Counties, moving
southeast at 15 mph.

HAZARD...Wind gusts up to 40 mph. Heavy snow showers.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Visibility reduced to less than one mile
         at times in falling and blowing snow will make for
         difficult driving conditions.

Locations impacted include...
Shelby, Cut Bank, Conrad, Chester, Browning, Valier, Kevin, Lothair,
Joplin, South Browning, Heart Butte, North Browning, Dupuyer,
Ethridge, Oilmont, Ledger, Galata, Santa Rita, Pendroy, and Ferdig.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Be prepared for rapidly changing driving conditions.

&&

LAT...LON 4876 11250 4888 11199 4861 11067 4807 11158
      4802 11270 4850 11317
TIME...MOT...LOC 2126Z 313DEG 14KT 4852 11191

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

SC