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FXUS65 KTFX 270611
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1210 AM MDT Thu Jun 27 2024

UPDATED AVIATION SECTION

.SYNOPSIS...

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.

&&

.Update...

Evening update has been published, with main adjustment being to
increase PoPs by 10-20%, predominately across Central and North
Central Montana, to account for more scattered coverage of showers
and thunderstorms this evening. Main impact from these showers and
thunderstorms so far has been gusty and erratic winds, with peak
gusts associated with precipitation generally ranging from
between 40-50 mph. With the approach of the midnight hour I expect
the gusty and erratic winds to become less frequent beneath the
shower and thunderstorm activity as the boundary layer and low
levels moisten; however, isolated threats for wind gusts of 40-50
mph will remain possible, especially across eastern areas of
Southwest, Central, and North Central Montana that have yet to see
any showers, thunderstorms, or outflow winds associated with
precipitation. - Moldan

&&

.AVIATION...
-- Changed Discussion --
27/06Z TAF Period

VFR conditions will mostly continue through at least 28/06Z across
North Central (KCTB, KHVR), Central (KLWT, KHVR, KGTF), and
Southwest (KBZN, KEKS, KWYS) Montana. However, brief periods of MVFR
conditions are possible with lingering showers and thunderstorms
through around 08Z. More mountain-obscuring low VFR/MVFR conditions
expected with widespread showers and thunderstorms associated with a
cold front passage between 12Z and 00Z. Most of these thunderstorms
will be capable of producing erratic gusts to 40 kt, lightning,
small hail, and heavy downpours. However, the stronger thunderstorms
will be along and east of a line from KHVR to KHLN to KBZN, where
gusts could exceed 45 kt at times with large hail and frequent
lightning. In the wake of the cold front, showers and storms will
decrease, as breezy and gusty westerly winds become more widespread.
-Coulston

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.
-- End Changed Discussion --

&&

.PREV DISCUSSION...
/ISSUED 525 PM MDT Wed Jun 26 2024/

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  57  73  49  64 /  40  90  10  50
CTB  56  70  48  61 /  50  70  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 /  30  90  20  40

&&

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

$$

http://www.weather.gov/greatfalls