517
FXUS65 KTFX 280233
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
833 PM MDT Thu Jun 27 2024

.SYNOPSIS...

Showers and thunderstorms diminish later this afternoon and
evening, but showery, windy, and much cooler conditions are
expected tonight into Friday, with most precipitation falling over
North-central Montana. Drier and milder weather is expected for
the first half of the weekend, followed by a return of more active
weather Sunday into early next week.

&&

.Update...

Strong and gusty west winds in wake of a Pacific front will continue
to be experienced through the remainder of the evening hours, with
some reductions in speeds expected near midnight within the
valleys of Southwest and Central Montana. Winds along the Rocky
Mountain Front have thus far remainder below High Wind criteria
this evening, with the latest NBM Max (24 hour) Wind Gust
probabilities for 55 mph or greater remaining below 65% for areas
west of the Interstate 15 corridor across Central and North
Central Montana. While a stronger wind gust (greater than 55 mph)
or two due to mountain wave activity is possible from late this
evening and into early Friday morning along the Rocky Mountain
Front, current probabilities and BUFKIT analysis continue to
support the idea of holding off on a High Wind Warning. The
aforementioned decrease in winds within the valleys of Southwest
and Central Montana will allow temperatures to cool into the 30s
to mid-40s through Friday morning, while the plains of Central and
North Central Montana remain near 50 degrees due to the continued
strong west winds. - Moldan

&&

.AVIATION...
28/00Z TAF Period

Showers and thunderstorms have largely pushed east of Southwest
through North Central Montana; however, and isolated shower/storm
will remain possible over the plains through approximately 03z
Friday, primarily over eastern portions of Central and North
Central Montana. Additionally, rain showers and an isolated
thunderstorm or two will continue along the Continental Divide north
of the Montana Hwy 200 corridor through much of the overnight hours.
Biggest impact to terminal operations over the next 9-12 hours will
be strong and gusty west winds, especially at the KCTB terminal
where frequent gusts of between 35-45kts will occur over this
timeframe. A southward advancing cold front beyond 09z Friday will
then bring a wind shift to more of the north, in addition to
lowering CIGS and additional chances for showers and an isolated
thunderstorms. These lowering CIGS, which are expected to fall as
low as LIFR/IFR/MVFR, will predominately impact the KCTB, KHVR,
KGTF, and KHLN terminals through Friday afternoon. Isolated mountain
obscuration through the overnight hours will become more widespread
in wake of the aforementioned cold front on Friday. - Moldan

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

&&

.PREV DISCUSSION...
/ISSUED 456 PM MDT Thu Jun 27 2024/

Showers and embedded thunderstorms continue to move through the
eastern portions of Central/North-central Montana this afternoon
while a much more isolated brand of activity is situated farther
to the west. Instability never really sufficiently recovered for
any widespread stronger to severe thunderstorm development, but
there were a a few instances of wind gusts over 40 mph and some
small hail along the Hi-Line and the southwest. This trend should
continue, with only isolated small hail and or wind gusts, if any,
for the remainder of the afternooon.

Post frontal westerly winds have already begun to increase and
westerly flow aloft will become stronger this evening and tonight
while the mid- level low moves along the Canadian border. This
will maintain breezy to windy conditions along the Rocky Mountain
Front and the plains during the overnight hours. Wind speeds
should generally stay in the 20 to 35 mph, except along the Rocky
Mountain Front and adjacent high plains where there is around a 60
to 80% chance for wind gusts exceeding 55 mph this evening into
the overnight hours. Given the higher criteria (75 mph) for high
winds along the Rocky Mountain Front and the lower wind exceedance
probabilities over the high plains, I opted for a Special Weather
Statement and weather stories to address the expected impacts.

Precipitation chances remain on the low side this evening before
wrap around moisture brings showers and stratiform rains southward
over northern areas as the night progresses. There will be
sufficient cold air aloft for some higher mountain snow over the
higher terrain of Glacier National Park, though accumulations look
to be negligible and impacts are expected to be limited to cool
and wet outback conditions.

Showers and perhaps a few thunderstorm will move deeper into
Central and North-central Montana on Friday while cool
northwesterly winds keep temperatures a good 10 to 20 degrees
below average for this time of year. H700 to H500 flow in the 40
to 45 kt range combined with cold air advection and lower end
shower/thunder activity may result in a few surface wind gusts
over 50 mph, mostly along the Hi- Line and Fergus/Judith Basin
Counties. There are no plans for high wind products on Friday
either with the expected isolated nature of higher end wind gusts
and NBM probabilities for criteria winds remaining well under 80%
at this time.

Transient ridging brings a period of lighter winds and drier
conditions Friday night and much of Saturday before a more
unstable southwesterly flow aloft develops ahead of the next
approaching Pacific weather system by Sunday and brings a return
of shower thunderstorm chances. Most ensembles favor a
northwesterly flow aloft for the first half of next week with
passing disturbances maintaining daily chances for showers and
thunderstorms and near to slightly below average temperatures.
- RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  51  61  43  74 /  10  80  10   0
CTB  50  61  42  70 /  60  90   0   0
HLN  51  68  45  84 /  10  30   0   0
BZN  41  68  40  81 /  10  10   0   0
WYS  33  65  34  80 /  10   0   0   0
DLN  40  69  40  82 /   0   0   0   0
HVR  53  63  43  74 /  40  70  10   0
LWT  46  59  38  71 /  10  50  10   0

&&

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

$$

http://www.weather.gov/greatfalls