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802
FXUS65 KTFX 262046
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
246 PM MDT Wed Jun 26 2024

.SYNOPSIS...

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Showers and thunderstorms will continue to occur across
Southwestern Montana through this evening. Isolated thunderstorms
will produce strong to severe wind gusts across Southwestern Montana
this afternoon and evening. Showers will spread north to Central and
North-central Montana this evening and continue through the
overnight period into Thursday morning. Isolated to scattered strong
to severe thunderstorms will affect North-central and Central
Montana on Thursday. Rain will continue across North-central and
Central Montana on Friday. Saturday and Sunday will warm up and be
mostly dry before a new weather system moves into the area for
early next week.
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&&

.DISCUSSION...

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This Afternoon... There will be strong to severe
thunderstorms across Southwestern Montana continuing through this
evening. A weak warm front will move through Southwestern Montana
and into Central and North-central Montana this evening. This warm
front will help to destabilize the atmosphere in Southwestern
Montana especially for areas south of I-90. Isolated thunderstorms
in Southwestern Montana south of I-90 will produce severe wind gusts
this afternoon through this evening. The Storm Prediction Center has
a Marginal Risk (5% chance within 25 miles of a point) for severe
wind gusts for those areas for this afternoon and evening. This
evening continuing into the overnight hours, these thunderstorms
will move north into Central and North-central Montana and become
isolated showers with a rumble of thunder or two. Due to an upper-
level ridge, today will be the warmest day of this forecast period
across Southwestern, Central, and North-central Montana. This
afternoon and evening locations across Southwestern Montana have a
10 - 30% chance for a tenth of an inch of rain or greater.

Thursday... An upper-level trough moves over North-central, Central,
and Southwestern Montana on Thursday. This combined with a strong
surface cold front will cool down temperatures across the area and
bring widespread precipitation to the area. It will also bring
isolated to scattered strong to severe thunderstorms across North-
central and Central Montana. These storms will begin Thursday
morning in Western North-central and Central Montana and spread
eastward through the morning and into the early to late afternoon.
Storms will end by late afternoon/early evening. The Storm
Prediction Center (SPC) has issued a Marginal Risk (5% chance
within 25 miles of a point) for severe hail and wind across
North- Central and Central Montana from Havre to Great Falls to
Butte and eastward across the rest of Eastern Montana. Across
Fergus, Eastern Meagher, and Eastern Judith Basin Counties the SPC
has issued a Slight Risk (15% chance within 25 miles of a point)
for Severe Hail and Severe Wind and a Marginal Risk (2% chance
within 25 miles of a point) for a tornado. Across Fergus County
there is 10% chance for hail lime size or greater (2+ inches in
diameter) and wind gusts greater than 75 mph. Additionally some of
these storms have a high chance to produce heavy rainfall. Across
the eastern half of North-central and Central Montana on Thursday
there is a 40 - 70% chance for a quarter inch of rain or greater.
Across the eastern half of Southwestern Montana there is a 20 -
50% chance for a quarter inch of rain or greater. On Thursday
along the Rocky Mountain Front there is a 70 - 90% chance for wind
gusts 55 mph or greater. Along the plains adjacent to the Rocky
Mountain Front there is a 25 - 50% chance for wind gusts of 55 mph
or greater.

Friday... On Friday the upper-level trough remains over North-
central, Central, and Southwestern Montana. This will cool down
temperatures to 10 - 15 degrees below seasonal averages. This will
also bring precipitation to North-central and Central Montana.
Due to strong winds aloft at 500 and 700 mb there will be gusty
winds with isolated locations having a 58 mph wind gust or
greater. Across isolated locations of North-central and Central
Montana there is a 40 - 80% chance for having wind gusts of 58 mph
or greater. Due to only isolated locations having severe wind
gusts no High Wind Products will be issued at this time. This will
need to continue to be monitored. Areas north of a line from the
Northern Cascade County border to the Northern Fergus County
border have a 20 - 50% chance for a quarter inch of rain or
greater. Due to the upper-level trough snow-levels will lower to
7500 - 8000 feet. This will bring snow to higher mountain peaks
across North-central, Central, and Southwestern Montana. There
will be a 10 - 20% chance for a tenth of an inch of snow or
greater across those locations on Friday. Backcountry hikers
should be prepared for snow and cold conditions on Friday. -IG

Saturday through next Wednesday... A broad high pressure ridge
between systems will bring dry conditions for Saturday and near
normal temperatures for Saturday into Sunday. However, a broad low
pressure trough will bring an increasing chance for showers and
thunderstorms again for Sunday through Tuesday, as temperatures cool
back to slightly below normal. As of now, the long-term model
guidance is forecast another broad high pressure ridge to dry out
the area and warm temperatures back slightly above normal for
Wednesday. -IG/Coulston
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&&

.AVIATION...
26/18Z TAF Period

VFR conditions will prevail across all terminals during this TAF
period. Wednesday across all terminals it will be warm and so there
will be density altitude issues from the beginning of the TAF period
through Wednesday evening. Across the Southwestern Montana terminals
(KBZN, KWYS, and KEKS) there will be isolated showers and
thunderstorms Wednesday afternoon through Wednesday evening. Due to
the isolated nature of these showers and thunderstorms only VCSH was
used in the TAFs. Some of the thunderstorms will produce strong to
severe wind gusts. For the KHLN terminal Wednesday evening there is
a 40% chance for a rain shower or two and so a PROB30 group was
included for it. There is a 20% chance for these showers to affect
the North-central Montana Terminals (KGTF, KHVR, KCTB, and KLWT)
Wednesday evening through early Thursday morning. Thursday morning
across all terminals there will be isolated showers and
thunderstorms. For the KHVR, KLWT, and KGTF terminals these
thunderstorms will be strong to severe with hail and wind gusts as
the primary threats. Some of the thunderstorms Thursday morning will
produce heavy rainfall and there is a low chance of intermittent
reductions in visibility to MVFR levels because of it. There will be
isolated instances of low-level wind shear across the Southwestern
Montana terminals (KBZN, KWYS, and KEKS) Thursday morning. -IG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
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GTF  57  73  49  64 /  30  80  10  50
CTB  55  70  48  61 /  30  60  30  80
HLN  60  76  51  69 /  50  80   0  20
BZN  55  78  43  69 /  40  80  20  10
WYS  47  74  35  66 /  80  50  10  10
DLN  52  75  39  70 /  40  50   0   0
HVR  57  75  50  65 /  40  90  20  80
LWT  55  74  43  61 /  20  90  20  40
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&&

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

$$

http://www.weather.gov/greatfalls