Severe Thunderstorm Warning 55, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
340 PM MDT Tue Aug 29 2023

.SYNOPSIS...

Dry, breezy, and very warm conditons are expected through late this
afternoon and evening when a Pacific cold front brings a period of
gusty showers and thunderstorms that will persist into the overnight
hours. Much cooler, showery, and windy conditions are then expected
Wednesday into Thursday. Temperatures warm back above average for
the first half of the weekend as widely scattered showers and storms
increase in a southwest to northeast fashion through Sunday.

&&

.UPDATE...

A Severe Thunderstorm Watch has been issued and is in effect until
900 PM MDT this evening for Beaverhead and Madison Counties.

The primary threats include scattered damaging wind gusts to 70
mph possible, and isolated large hail to 1 inch in diameter
possible.
- Fogleman

&&

.AVIATION...
520 AM MDT Tue Aug 29 2023 (29/12Z TAF Period)

VFR conditions prevail through this afternoon beneath an increasing
southerly flow aloft with just some scattered mid level clouds.
Higher concentrations of wildfire smoke across NE MT may briefly
affect KHVR this morning with MVFR visibility. Southerly surface
winds increase at all terminals this afternoon through this evening
ahead of a Pacific cold front expected to cross the region this
evening and overnight. Strong wind gusts are possible with showers
and thunderstorms associated with the frontal passage along with a
period of lower ceilings and mountain obscurations. West winds
develop overnight behind the front and increase through the day on
Wednesday. Hoenisch

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

&&

.PREV DISCUSSION...
/ISSUED 225 PM MDT Tue Aug 29 2023/

After a slow start eroding morning inversions, temperatures are
starting to rise toward forecast highs and winds and humidity are
now yielding marginally critical fire weather conditions over the
northeastern portions of the CWA. The very warm and dry conditions
will persist through this evening when the well advertised
Pacific front, currently approaching Western Montana, will
traverse the forecast area from west to east between 5 pm and
midnight tonight. Locations west of I15 are still expected to see
the strongest gusts from the cold front and associated showers and
thunderstorms and gusts up to 70 mph can't be ruled out with the
stronger cells. SPC has maintained a 'slight risk' (15% chance
within 25 miles of a given point) for wind gusts over 58 mph for
much of Beaverhead County. Atmospheric instability will fall off
as the front moves eastward later this evening, but there will
still be sufficient cold air advection and overall frontal
momentum to transfer at least isolated instances of severe wind
gusts over the plains and the eastern portions of Southwest
Montana. Tracking this evening's severe weather will be on the
tricky side as there may not be a lot of lightning or heavy rain
with today's showers/storms and wind gusts may outrun the cells
themselves by quite a distance.

The front should clear the CWA by Wednesday morning with cooler
but windy conditions across the area Wednesday through Thursday as
the upper low center lifts out through NW MT into southern AB.
30-45 mph wind gusts are expected across much of Central and
Southwest Montana Wednesday through early Thursday. The strongest
winds are still expected along the immediate east slopes of the
Rocky Mtn Front and the downslope areas over and near the central
ranges where there is a greater than 50% probability of gusts
exceeding 55 mph. Strongest winds in these areas will likely occur
tonight during a period of more favorable conditions for
downslope wind enhancement. A High Wind Warning was issued for the
Rocky Mtn Front, the northern high plains, and Cascade/Judith
Basin County lower elevation zones for Wednesday through noon
Thursday. There will be periods of strong wind potential separated
by lulls within this timeframe.
- RCG/Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  57  71  52  77 /  60  30  30   0
CTB  56  64  52  73 /  90  40  40  10
HLN  57  74  53  80 /  80  20  20   0
BZN  52  76  45  78 /  70  10  10   0
WYS  42  66  32  69 /  50  10   0   0
DLN  47  70  40  75 /  80   0   0   0
HVR  60  76  53  81 /  70  40  40  20
LWT  55  75  50  77 /  80  20  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 6 AM Wednesday to noon MDT Thursday for
Eastern Glacier, Western Toole, and Central Pondera-Northern
High Plains-Southern High Plains.

Red Flag Warning until 1 AM MDT Wednesday for Hill and Blaine
Counties.

High Wind Warning from 10 AM Wednesday to noon MDT Thursday for
Cascade County below 5000ft-Judith Basin County and Judith Gap.

&&

http://www.weather.gov/greatfalls

Special Weather Statement
National Weather Service Great Falls MT
505 PM MDT Tue Aug 29 2023

MTZ327>329-292345-
Ruby Mountains and Southern Beaverhead Mountains MT-
Northwest Beaverhead County MT-
Beaverhead and Western Madison below 6000ft MT-
505 PM MDT Tue Aug 29 2023

...A line of thunderstorms will impact portions of western
Beaverhead County through 545 PM MDT...

At 504 PM MDT, Doppler radar was tracking showers and a few strong
thunderstorms along a line extending from near North Fork to near
Leadore to 17 miles south of Gilmore, all in Idaho. Movement was
northeast at 40 mph.

HAZARD...Winds in excess of 40 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Wisdom, Jackson, Dell, Grant, Bannack Pass, Polaris, Bannack, Clark
Canyon, and Bannack State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
southwestern Montana.

&&

LAT...LON 4445 11300 4477 11313 4482 11324 4479 11335
      4487 11346 4494 11349 4496 11344 4506 11345
      4513 11358 4533 11374 4550 11376 4552 11383
      4559 11380 4562 11386 4586 11359 4507 11271
      4449 11257 4448 11278 4436 11284
TIME...MOT...LOC 2304Z 222DEG 37KT 4534 11402 4466 11327 4422 11314

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

SC

Special Weather Statement
National Weather Service Great Falls MT
522 PM MDT Tue Aug 29 2023

MTZ307-315-292345-
Southern Rocky Mountain Front MT-
Upper Blackfoot and MacDonald Pass MT-
522 PM MDT Tue Aug 29 2023

...A cluster of strong thunderstorms will impact portions of west
central Lewis and Clark County through 545 PM MDT...

At 521 PM MDT, Doppler radar was tracking isolated strong
thunderstorms clustered near Lincoln, or 27 miles northeast of
Drummond, moving north at 15 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Lincoln.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4722 11286 4716 11234 4679 11249 4679 11253
      4684 11254 4683 11279 4702 11280 4717 11279
      4718 11286
TIME...MOT...LOC 2321Z 188DEG 14KT 4691 11269

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

SC

Special Weather Statement
National Weather Service Great Falls MT
547 PM MDT Tue Aug 29 2023

MTZ327>330-300030-
Ruby Mountains and Southern Beaverhead Mountains MT-
Gallatin and Madison County Mountains and Centennial Mountains MT-
Northwest Beaverhead County MT-
Beaverhead and Western Madison below 6000ft MT-
547 PM MDT Tue Aug 29 2023

...A line of showers and thunderstorms with strong gusty winds will
impact portions of southwestern Madison and Beaverhead Counties
through 630 PM MDT...

At 546 PM MDT, Doppler radar was tracking scattered showers with a
few strong thunderstorms along a line extending from 16 miles
northwest of Wisdom to 15 miles southwest of Lima. Movement was
northeast at 40 mph.

HAZARD...Winds in excess of 40 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Dillon, Lima, Jackson, Monida, Wisdom, Dell, Grant, Bannack Pass,
Melrose, Wise River, Dewey, Bannack, Snowline, Glen, Beaverhead Rock
State Park, Polaris, Clark Canyon, Bannack State Park, and Monida
Pass.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
southwestern Montana.

&&

LAT...LON 4445 11300 4477 11313 4479 11335 4487 11346
      4506 11345 4533 11375 4575 11392 4594 11351
      4575 11336 4578 11336 4588 11310 4576 11277
      4563 11270 4568 11258 4463 11186 4454 11211
      4457 11229 4445 11239 4450 11274 4436 11285
TIME...MOT...LOC 2346Z 216DEG 36KT 4580 11365 4444 11274

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

SC

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