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345
FXUS65 KTFX 260910
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
310 AM MDT Sun May 26 2024

.SYNOPSIS...

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Today it will breezy and mostly sunny for all but the Hi-
Line where there will be showers and thunderstorms this afternoon
and evening. There will be gusty winds along the Rocky Mountain
Front Today and Wednesday. Monday through Tuesday it will warm up
with thunderstorm chances Tuesday afternoon and evening. Wednesday
through Friday there will be an upper-level trough in place that
will cool down temperatures and bring showers and thunderstorms to
the area.
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&&

.DISCUSSION...

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Today through Memorial Day... This morning in the
Gallatin Valley and portions of far Southwestern Montana fog could
form after skies clear. Some model soundings and probabilistic
guidance show the potential for this fog while others do not. Only
for isolated locations in those areas fog has the potential to
reduce visibility down to a half mile or less. Today an upper-level
ridge begins to move into the area above North-central, Central, and
Southwestern Montana. Ahead of this ridge there is an upper-level
shortwave that will move across the Hi-Line this afternoon and
evening bringing rain showers and thunderstorms. For everywhere else
outside of the West Yellowstone area it will be mostly sunny and
slightly cooler than seasonal averages. Due to a moderately strong
surface gradient there will gusty winds primarily along the Rocky
Mountain front Today. Along the Rocky Mountain Front there is a 70 -
90% chance for wind gusts exceeding 55 mph Today. Along the plains
adjacent to the Rocky Mountian Front there is 30 - 50% chance for
wind gusts exceeding 55 mph Today. Elsewhere across portion of North-
central and Central Montana there is 40 - 70% chance for wind gusts
exceeding 47 mph Today. On Memorial Day the upper-level ridge
remains in place over North-central, Central, and Southwestern
Montana. Memorial Day will be sunny and dry across the area with
about seasonal average temperatures.

Tuesday through Wednesday... On Tuesday the upper-level ridge
remains in place over North-central, Central, and Southwestern
Montana and so temperatures will continue the warming trend. On
Tuesday across North-central Montana there is a 95% chance for
temperatures 80 or greater in the Golden Triangle Region of Central
and North-central Montana (Cut Bank to Great Falls to Havre) and the
Helena and Gallatin Valleys. Tuesday late afternoon through
Wednesday morning a cold front begins to move east across North-
central, Central, and Southwestern Montana. This combined with
southwest flow aloft will cause the atmosphere to become unstable.
This will result in the potential for thunderstorms some of which
could be severe. These thunderstorms have the potential to occur
Tuesday late afternoon through the evening. At this time it appears
unlikely that there will be widespread severe thunderstorms on
Tuesday. On Tuesday there is a 10 - 30% chance for locations across
North-central, Central, and Southwestern Montana receiving a tenth
of inch of rain or greater. Monitor the forecast for updates.

On Wednesday an upper-level trough associated with the cold front
begins to move over North-central, Central, and Southwestern
Montana. This will bring cooler temperatures and rain to most of the
area on Wednesday. Along and south of the Highway 200 Corridor in
Central Montana there is 30 - 50% chance for a half inch of rain or
greater on Wednesday. Other locations of North-central, Central, and
Southwestern Montana have a 20 - 40% chance for seeing a quarter
inch of rain or more on Wednesday. On Wednesday due to strong flow
aloft and a strong surface pressure gradient there is a 60 - 80%
chance for wind gusts exceeding 55 mph along the Rocky Mountain
Front. Along the plains adjacent to the Rocky Mountian Front there
is a 65% chance for wind gusts exceeding 47 mph on Wednesday.
Wednesday afternoon and early evening along with the rain there is
the potential for thunderstorms some of which could be severe.
Continue to monitor the forecast for details.

Thursday through next Sunday... On Thursday the upper-level trough
remains in place over North-central, Central, and Southwestern
Montana. Showers and thunderstorms are possible across the area on
Thursday. The thunderstorms will not be severe. On Thursday there is
a 20 - 40% chance for locations across North-central, Central, and
Southwestern Montana receiving a tenth of an inch of rain (total
liquid for mountain locations) or more. On Thursday for the
mountains of North-central, Central and Southwestern Montana there
is 40 - 60% chance for receiving a tenth of an inch of snow or more.
On Friday clusters indicate that an upper-level trough remains in
place over North-central, Central, and Southwestern Montana which
will keep unsettled weather in place for the area on Friday. On
Saturday two clusters (66% of ensemble members) have an upper-level
ridge in place over North-central, Central, and Southwestern
Montana. The other two clusters (44% of ensemble members) have the
upper-level trough remain in place over the area on Saturday. This
indicates uncertainty in the weather for Saturday at this time. Next
Sunday three clusters (80% of ensemble members) have an upper-level
ridge over North-central, Central, and Southwestern Montana. Next
Sunday one cluster (20% of ensemble members) has the upper-level
trough remaining over the area. This indicates that by Sunday the
weather pattern will most likely change to have warm and calm
weather for North-central, Central, and Southwestern Montana. -IG
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&&

.AVIATION...
26/06Z TAF Period

VFR conditions are expected through at least 27/06Z across North
Central (KCTB, KHVR), Central (KLWT, KGTF, KHLN), and Southwest
(KBZN, KEKS, KWYS) Montana, unless otherwise noted.

Earlier shower and thunderstorm activity has moved east out of the
area, allowing skies to partially clear. However, another weak
disturbance in the westerly flow aloft is forecast to bring
scattered showers to Southwest Montana again through 11Z or so,
possibly causing brief periods of MVFR conditions. Partial clearing
there after 11Z could cause areas of fog to form, but there is still
uncertainty as to just how dense it will become due to the
uncertainty as to the degree of clearing, so will hold off on
significant reduction to visibility for now at the terminals.

Otherwise, another disturbance is forecast to move east along the
Canadian border through the day on Sunday, which will increase
westerly winds across the area. As the winds increase on the Rocky
Mountain Front, there will be a period of low level wind shear there
through 12Z or so. After 15Z, wind gusts will mostly be in the 20 to
30 kt range, likely exceeding 35 kt on the Rocky Mountain Front.
However, this disturbance will also bring a chance for afternoon
showers and thunderstorms to the Hi-Line area (including KHVR).
Winds, clouds and showers should decrease after 02Z. -Coulston

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

&&

.PRELIMINARY POINT TEMPS/POPS...
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GTF  63  40  72  45 /  10   0   0   0
CTB  60  39  70  42 /  10   0   0   0
HLN  65  44  75  48 /  10   0   0   0
BZN  64  37  71  41 /  10   0   0   0
WYS  55  32  65  35 /  20   0   0   0
DLN  62  37  72  41 /   0   0   0   0
HVR  65  42  73  45 /  30  10   0   0
LWT  59  37  66  43 /  10   0   0   0
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&&

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

$$

http://www.weather.gov/greatfalls