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000
FXUS65 KTFX 211426
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
826 AM MDT Sun Apr 21 2024

.UPDATE...

Satellite imagery shows a fairly potent mid level shortwave
emerging east of the Canadian Rockies in southern Alberta this
morning with evidence of mountain wave effects in the fast flow to
its south across Glacier county and adjacent areas. At the
surface, low pressure is developing in central AB with its
associated cold front extending south across Glacier county and
southwest into western MT. This aligns well with the previous
forecast and incoming models this morning with the front and it`s
associated wind shift and increase in west winds spreading across
much of central and north-central MT by mid-day. Strongest wind
gusts today still look to occur along the the Rocky Mtn Front and
extending east through Glacier and northern portions of Toole and
Liberty counties, where a High Wind Warning is in effect through
this evening. The front pushes through southwest MT this afternoon
with afternoon terrain heating and weak instability supporting a
few showers and possibly an isolated thunderstorm south of I-90
with areas around Big Sky having the highest probability (20-30%)
of seeing a thunderstorm late this afternoon. Hoenisch

&&

.SYNOPSIS...
Today there will be strong winds and wind gusts along the Rocky
Mountain Front and adjacent plains with slightly less strong winds
and wind gusts across the plains of North-central Montana. Tomorrow
Hill and Blaine Counties will have strong winds and wind gusts.
Temperatures warm up from Monday to Wednesday with mostly dry
weather until unsettled conditions close out the week with a pattern
change likely Friday into Saturday.

&&

.AVIATION...
520 AM MDT Sun Apr 21 2024 (21/12Z TAF Period)

Expect increasing surface winds this morning, with strong surface
winds expected over the western half of North Central MT by mid day.
The strong winds will diminish a bit this evening. There is a small
chance for a light shower over the Rocky Mountain Front and also in
the mountains around Ennis/Big Sky. Otherwise, dry conditions are
expected elsewhere. The mountains around the Rocky Mountain front
and Big Sky could be obscured at times. Brusda

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

&&

.PREV DISCUSSION...
/ISSUED 520 AM MDT Sun Apr 21 2024/
Today and Monday...Today there is an upper-level low and surface
cold front that will move through North-central, Central, and
Southwestern Montana. As a result of the front and low combined with
strong 700 and 500 mb winds, there will be strong winds and wind
gusts along the Rocky Mountain Front and adjacent plains and in
Toole and Liberty counties. As a result a High Wind Warning is in
effect for those locations from 7 AM this morning until Midnight
tonight. In addition across the eastern portion of the Hi-line there
is 70 - 90% chance of wind gusts exceeding 45 mph today. Across the
Montana Highway 200 Corridor there is a 60 - 80% chance of wind
gusts exceeding 45 mph today. Across the eastern portion of Hi-line
there is a 90% chance for sustained winds exceeding 30 mph and
across the Montana Highway 200 corridor there is a 65 - 85% chance
of sustained winds exceeding 30 mph. Associated with the cold front
there will be light snow showers along the Northern Rocky Mountain
Front where there is a 80% chance for greater than a tenth of an
inch of snow. Additionally, associated with the cold front there is
a 15 to 30% chance for greater than a trace of rain across the
eastern portion of Southwestern Montana. By midnight the strong
winds and wind gusts will diminish.

On Monday the upper-level low moves to the east of North-central,
Central, and Southwestern Montana with mostly zonal flow replacing
the low. On Monday due to strong 700 mb winds and a strong pressure
gradient Hill and Blaine Counties will have strong winds and wind
gusts. However, due to a lack of mixing of the winds down to the
surface due to cloud cover, winds are unlikely to exceed High
Warning Criteria. So a High Wind Warning was not issued. However,
isolated portions of Blaine County could briefly have sustained
winds exceeding 40 mph and/or wind gusts exceeding 58 mph. The
probability for wind gusts exceeding 45 mph in Hill and Blaine
Counties on Monday is 50 - 90% with the higher probabilities the
further east you go across those two counties. The probability for
sustained wind speeds exceeding 30 mph in Hill and Blaine
Counties on Monday is 75 - 90%. On Monday across most of North-
central Montana there is a 10 - 25% chance for greater than a
trace of rain.

Tuesday through Thursday... On Tuesday an upper-level ridge will
move over North-central, Central, and Southwestern Montana. This
will allow temperatures to warm up slightly with dry weather and
clear skies across the area on Tuesday. On Wednesday the upper-level
ridge remains in place over North-central, Central, and Southwestern
Montana. Embedded in the ridge there is a shortwave. This shortwave
will bring rain and potentially thunderstorms in Central and
Southwestern Montana on Wednesday. At this time there is
uncertainty in the likelihood and impacts of thunderstorms. On
Wednesday temperatures will be the warmest of the week. On Wednesday
most of the lower-elevations of North-central, Central, and
Southwestern Montana have a 70 - 90% chance for temperatures 70
degrees or greater. On Wednesday across the lower elevations along
and south of the Montana Highway 200 Corridor there is a 10 - 20%
chance for a tenth of an inch of rain or greater. On Thursday the
upper-level ridge begins to move eastward out of the area above
North-central, Central, and Southwestern Montana. On Thursday along
and south of the Montana Highway 200 Corridor and west of US Highway
191 south of Bozeman there is a 10 - 20% chance for a tenth of an
inch of rain or greater. For the lower-elevations from the Bozeman
area south to the West Yellowstone area there is a 20 to 30% chance
of two tenths of an inch of rain or greater on Thursday. For the
Gallatin and Madison ranges there is a 20 - 50% chance for a
tenth of an inch of snow or greater on Thursday.

Friday through next Sunday...On Friday clusters indicate that an
upper-level trough will begin to move above North-central, Central,
and Southwestern Montana. The clusters differ in the strength and
timing of this trough. However, this indicates that the weather
pattern will change on Friday. On Saturday clusters indicate that
the upper-level trough will be over North-central, Central, and
Southwestern Montana. This indicates that most likely Friday and
Saturday will be wet and cooler than Thursday across the area. On
Sunday clusters indicate that most likely the upper-level trough
moves out of above North-central, Central, and Southwestern Montana.
This will need to be monitored for forecast updates. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  57  32  56  30 /   0   0   0   0
CTB  52  32  54  27 /   0   0   0   0
HLN  61  32  59  32 /   0   0   0   0
BZN  65  25  57  26 /  20  10   0   0
WYS  56  22  52  19 /  20  20   0   0
DLN  64  26  57  29 /  10   0   0   0
HVR  61  34  57  30 /   0   0  10   0
LWT  59  29  51  28 /  10  10  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until midnight MDT tonight for East Glacier
Park Region-Eastern Glacier, Western Toole, and Central Pondera-
Eastern Toole and Liberty-Northern High Plains-Southern High
Plains.

&&

$$

http://www.weather.gov/greatfalls