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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS65 KTFX 211958
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
158 PM MDT Sun Apr 21 2024

.SYNOPSIS...

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Low pressure moving across southern Alberta and Saskatchewan will
maintain windy conditions across the area through Monday with
strongest winds continuing along the Rocky Mountain Front and near
the Alberta border through this evening. Except for a few isolated
showers across parts of southwest Montana early this evening, mainly
dry conditions prevail through Wednesday with temperatures gradually
warming back above seasonal averages by the middle of this week.
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&&

.DISCUSSION...

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Satellite imagery showed lee-cyclogenesis occurring this morning
over southern Alberta as a fairly potent shortwave disturbance
emerged east of the Canadian Rockies. This feature further develops
into a closed upper low as it tracks east across southern SK tonight
through Monday morning, with the primary impact being the
maintenance of very windy conditions across north-central MT. By
late this afternoon, the cold front that pushed through north-
central and central MT this morning will continue across Southwest
MT, where limited moisture and instability will support some showers
with the frontal passage, primarily south of I90. High resolution
model ensembles continue to give the highest probability (20-30%)
for isolated thunderstorms near the Big Sky area between 4pm and
7pm.

Clouds decrease from north to south this evening with winds turning
a bit more northwesterly and decreasing late this evening across
southwest MT. Winds will be slow to decrease however across north-
central MT tonight as the low moving across SK continues to deepen,
maintaining a fairly strong pressure gradient to its southwest
across N-central MT. The strongest winds through this evening will
continue across areas from the Rocky Mtn Front east along the
Canadian border where a High Wind Warning is in effect through
midnight. Expect the strong winds to wane this evening but gusts in
excess of 40 mph will remain a possibility in these areas even
after midnight.

Temperatures will be just slightly cooler on Monday in the wake of
todays cold front with breezy to windy conditions persisting across
north-central MT and developing across SW MT in the afternoon. There
is a 50% or higher probability for wind gusts in excess of 40 mph
across eastern portions of north-central MT Monday afternoon with
similar probabilities for gusts in excess of 50 mph across
portions of Blaine county. Upper level ridging gradually builds
across the area Monday night through Wednesday for a period of dry
conditions with lighter winds and warming temperatures.
Temperatures still look to peak on Wednesday around 10 degrees
above seasonal averages.

Medium range model ensembles remain in good agreement with the large
scale pattern evolution late this week into the weekend, developing
upper troughing with increasing depth across the western US and an
overall cooler and wetter weather pattern by the weekend. This begins
with a pair of systems passing largely north and south of the area
late this week which begin to import moisture back into the region
for showers and potentially some thunderstorms with temperatures
initially only cooling back to seasonal averages. By next weekend,
larger difference develop among models in the handling of additional
energy coming into and deepening through. While there is still too
much uncertainty for more specific details, the potential for
widespread precipitation and cooler than averages temperatures is
increasing for next weekend. Hoenisch
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&&

.AVIATION...
1135 AM MDT Sun Apr 21 2024 (21/18Z TAF Period)

Gusty surface winds will continue through the rest of the day across
north-central Montana as a cold front continues to make its way
across the area. Gusts up to 50kts are possible for KCTB with gusts
up to 40kts possible for KGTF and KHVR. Winds will diminish a little
after sunset, however, gusts up to 30kts at KGTF/KHVR and 40kts at
KCTB are possible overnight.

Across central Montana (KHLN, KLWT), breezy conditions will persist
through the day with gusts up to 30kts for KLWT and gusts up to
25kts for KHLN.

Dry conditions will continue for north-central and central Montana
with mid- and high-level cloud decks persisting through most of the
TAF period.

For southwestern Montana (KBZN, KEKS), there is a slight chance for
showers in the mountains surrounding both terminals, however, there
was not enough confidence in impacts to the terminals to add them to
the TAFs. Mountain obscuration will be possible at times related to
these showers which have the greatest chance of occurring between
21/21Z and 22/00Z. After 22/00Z, dry conditions will return and
persist across southwestern Montana for the remainder of the TAF
period.

-thor

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

&&

.PRELIMINARY POINT TEMPS/POPS...
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GTF  33  56  30  62 /   0  10   0   0
CTB  32  54  28  60 /   0   0   0   0
HLN  32  57  32  64 /   0   0   0   0
BZN  25  57  26  62 /  10   0   0   0
WYS  21  52  20  57 /  20   0   0   0
DLN  27  57  29  62 /   0   0   0   0
HVR  34  57  31  64 /   0  10   0   0
LWT  29  51  28  57 /   0   0   0   0
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&&

.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