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080
FXUS65 KTFX 230940
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
340 AM MDT Sun Jun 23 2024

.SYNOPSIS...

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Today is the warmest day of the week ahead, with low elevation high
temperatures ranging from the upper 80s to mid 90s, while drying
continues through tomorrow. Gusty winds are forecast, today and
tomorrow, as well. Afternoon and evening thunderstorms develop.
Today, a few thunderstorms may become severe, producing erratic
high winds, large hail and frequent lightning.
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&&

.DISCUSSION...

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

Today and Tomorrow...Begin this Sunday under the influence of
upper level ridging, with an upper level trof approaching from
the west. Temperatures continue to warm, today, and low elevation
highs reach into the 90s across much of the region. North central,
central and southwest Montana, generally, fall under an area of
Minor Heat Risk. This is the level that primarily affects those
individuals who are extremely sensitive to heat. Isolated areas of
central and southwest Montana are included under a Moderate Heat
Risk for today. This is the level of heat that affects most
individuals sensitive to heat, especially those without effective
cooling and/or adequate hydration. Special attention and care
should be given to the young, the elderly and pets. A closed area
of upper level higher heights is located over Texas, and the
associated ridge presses northward into our region. This ridge
adds mass to the approaching trof, causing said trof to pass along
Montana`s northern border. The result is a strong westerly cross
barrier flow that pours into our region. Strong, non-warning
criteria, gusty winds are forecast, especially across the Northern
Rocky Mountain Front and the adjacent plains. Gusty winds
continue into tomorrow. As the day progresses, the atmosphere
becomes more unstable, and afternoon and evening thunderstorms
develop. A few thunderstorms may become severe, as there is a 5%
chance for erratic high winds of 58 mph or more, as well as, a 5%
chance for large hail of an inch or greater in diameter, with some
storms. The best chance for severe thunderstorm activity occurs
across Blaine and Fergus counties. General thunderstorms are
forecast to develop tomorrow afternoon and evening, with the best
chance for thunderstorm development focused more on southwest
Montana and northeastward along Meagher, Judith Basin and Fergus
Counties.

Tuesday and Wednesday...The mid week period is characterized by
warming conditions, courtesy of an overhead ridge, and an upper
level southwesterly flow. Tuesday, is forecast to be a, generally,
quiet summer day. Wednesday, breezy winds, as well as, afternoon
and evening thunderstorms and rain showers are forecast, as the
atmosphere becomes more unstable under the influence of the
dynamics associated with the leading edge of the next upper level
trof.

Thursday and Friday...While the previously mentioned trof rolls
across the region, temperatures cool, gusty winds develop and
wide spread rain showers impact the region. There is a 20% to 40%
chance of afternoon and evening thunderstorm activity.

Saturday and next Sunday...The next upper level ridge moves
quickly through the area, followed by the next trof. Saturday,
looks to be a mild and breezy summer day, while Sunday offers some
more active weather.
-Fogleman
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&&

.AVIATION...
23/06Z TAF Period

VFR conditions are generally forecast to continue through at least
24/06Z across North Central (KCTB, KHVR), Central (KLWT, KGTF,
KHLN), and Southwest (KBZN, KEKS, KWYS) Montana, unless otherwise
mentioned.

A shortwave low pressure trough will gradually move across the
Pacific Northwest through the period, causing the southwesterly flow
aloft to increase. The main concern for aviation from this will be
an increasing threat for mountain wave turbulence after 18Z,
especially over North Central and Central Montana, as well as an
increasing threat for low-level wind shear after 00Z on the Rocky
Mountain Front and across the Hi-Line as winds start to decouple.
Also, with temperatures warming into the mid 80s to lower 90s for
most lower elevations, density altitude issues are possible.

Otherwise, areas of high- and mid-level cloudiness will mainly pass
overhead. However, a few strong thunderstorms could develop between
20Z and 04Z east of a KGTF to KHVR line, including the KLWT area,
likely causing strong erratic wind gusts and possibly causing brief
heavy downpours and hail, which may cause brief periods of MVFR
conditions. -Coulston

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

&&

.PRELIMINARY POINT TEMPS/POPS...
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GTF  90  53  83  48 /   0   0   0   0
CTB  83  48  76  45 /   0   0   0   0
HLN  95  58  88  53 /   0   0   0   0
BZN  93  53  88  49 /  10  10  10   0
WYS  84  47  81  43 /   0   0  10   0
DLN  90  53  87  48 /   0   0   0   0
HVR  92  55  83  50 /  10   0   0   0
LWT  89  53  79  48 /  20  30   0   0
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&&

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

$$

http://www.weather.gov/greatfalls