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FXUS65 KTFX 220558
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1157 PM MDT Fri Jun 21 2024

...Aviation Section Update...

.SYNOPSIS...
Showers and thunderstorms will continue to move across North Central
Montana through this evening, bringing the chance of strong winds
and destructive hail as they roll through. Beyond tonight, expect
temperatures to be on the rise as upper level ridging builds across
the Western United States.

&&

.UPDATE...

While the overall severe weather threat has ended for our area
for today, a few lingering strong thunderstorms continue for
Judith Basin and Fergus counties for the next 2 to 3 hours before
diminishing for the night. Primary concerns continue to be heavy
rainfall, hail, and wind. Please continue to monitor the forecast
and have multiple ways to receive warnings for thunderstorms if
they do become severe within the next 1 to 3 hours. There are also
a few rain showers along the MT/Canadian border that will
continue to move across the Hi-Line through the next 2 to 5 hours.
Otherwise, a cool and comfortable night is in store for North
Central and Southwest Montana. A few locations across North
Central Montana could see some patchy fog tomorrow morning with
clearing skies tonight, but will be localized to locations that
saw precipitation. Webb

&&

.AVIATION...
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22/06Z TAF Period

Note: The NWS Great Falls Weather Forecast Office manages the
following TAFs: KCTB, KHVR, KGTF, KLWT, KHLN, KBZN, KEKS and KWYS.

VFR conditions prevail at all airfields throughout this TAF period.
Morning fog is forecast to settle in over areas that lie near water
sources. Fog is not anticipated to impact our airfields. While
winds, generally, remain light, this afternoon and evening, winds
gusting to 20KT/25KT are forecast across southwest Montana,
impacting our general aviation community. As the weekend progresses,
a warming trend pushes low elevation temperatures into the 80s and
90s, favoring density altitude impacts.
- Fogleman

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

.PREV DISCUSSION...
/ISSUED 455 PM MDT Fri Jun 21 2024/

Key Points:

-Strong to severe thunderstorms are expected this afternoon and
 evening across North Central Montana, bringing the potential for
 destructive hail, strong winds, and even a low chance of a
 tornado

-Upper level ridging builds in next week, bringing warm and dry
 conditions to the Treasure State

Through Sunday Big concern in the short term continues to be the
potential for strong to severe thunderstorms, especially across
the North Central Plains south of US-2. Satellite imagery late
this morning was showing an early start to the convection along
the US-2 corridor and over the Little Belt Mountains, with dew
points across the plains creeping up into the mid 50s, indicating
that sufficient low level moisture is in place across the plains
to support these storms as they begin to grow through the
afternoon and evening hours. Given current forecast atmospheric
profiles (aka soundings), the atmosphere seems to be primed for
the development of a few scattered supercell thunderstorms, thanks
to modest but present directional shear and ample instability
(with CAPE/instability values nearing/exceeding 1500-2000 J/kg,
which is a bit higher than values we usually see in this area),
with wind speed with height (hodographs) indicating that the winds
in the atmosphere will be supportive of rotating
updrafts/supercells. While supercells are capable of producing any
type of severe weather, including strong winds, destructive hail,
and tornadoes, the atmosphere appears most primed for destructive
hail and potentially wind, depending on if the supercell winds
are actually able to reach the ground. While a tornado or two
cannot be ruled out, this threat should be held back by cloud
bases generally above 3000 feet above the ground. However, cloud
bases will be a little lower in the Judith Gap/Lewistown/Grass
Range area, which may make the atmosphere a bit more favorable to
the development of a tornado, if a supercell is able to make full
use of the atmospheric dynamics, especially with the presence of
an existing boundary from yesterdays storms that moved through
the area. Storms will remain possible through the afternoon and
evening hours before weakening and/or moving eastward by midnight
or so.

Across the southwest today, expect a few showers and
thunderstorms, especially across the higher terrain, though upper
level flow will be less conducive to the longer lived type of
storms that will be found across the plains.

Beyond today, upper level ridging will begin to build in across
the Intermountain West, which will allow temperatures to be on the
increase through the weekend. Expect most areas to reach the 80s
on Saturday with all but the Plains adjacent to the Rocky Mountain
Front reaching the low to mid 90s on Sunday with relative
humidity values dipping into the low 20s and teens. Ludwig

Monday through Wednesday...In response to the building upper level
closed area of higher heights over Arizona/New Mexico, an upper
level ridge dominates The Treasure State. Low elevation high
temperatures continue in the 80s and 90s, through mid-week, while
conditions remain dry for our region.

Thursday and Friday...As the end of the week approaches, the next
upper level trof enters the region, temperatures cool a bit, and
widespread rainfall is forecast.
- Fogleman

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  49  82  55  92 /  30   0   0   0
CTB  44  80  50  85 /  50   0   0   0
HLN  53  87  57  96 /  10   0   0  10
BZN  49  85  53  95 /  10   0   0  10
WYS  40  78  44  84 /  10   0   0  10
DLN  47  85  51  91 /   0   0   0   0
HVR  49  82  55  94 /  60  10   0  10
LWT  48  77  54  90 /  50  10   0  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

http://www.weather.gov/greatfalls