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000
FXUS65 KTFX 220543
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1143 PM MDT Sun Apr 21 2024

...Updated Aviation Section...

.SYNOPSIS...
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.

&&

.UPDATE...
1055 PM Update...The high wind warning has been cancelled.
Widespread strong winds are no longer expected. Brusda

830 PM Update...A low pressure system moving southeastward through
the Canadian Prairies will maintain gusty surface winds along the
Rocky Mountain Front and the plains overnight tonight, though wind
magnitudes will continue to slowly fall off with the loss of diurnal
mixing. The High Wind Warning was left in effect as winds are still
gusting to near 50 mph in a few spots and an another mountain wave,
similar to the one that brought 40 mph sustained winds and 50 kt
gusts to the Cut Bank area earlier, can`t be ruled out over the next
hour or so. The previous forecast package continues to handle the
current situation well, so no amendments are needed this evening. -
RCG

&&

.AVIATION...
1143 PM MDT Sun Apr 21 2024 (22/06Z TAF Period)

VFR conditions prevail across all terminals during this TAF period.
The primary concern for this TAF period is gusty winds at all
terminals due to a strong surface pressure gradient. Winds will gust
up to 25 kts at the KEKS, KGTF, KHLN, and KBZN terminals during the
majority of this TAF period. However at the KGTF terminal gusty
winds will end by 11AM Monday morning. Winds at the KCTB, KHVR, and
KCTB terminals will gust up to 33 kts during this TAF period with
wind gusts decreasing by Monday evening. There will be isolated
instances of low-level wind shear at the beginning of this TAF
period around the KCTB terminal. There will be instances of low-
level wind shear at the KHVR terminal primarily between 4AM and 10AM
Monday morning. There will scattered to few high-level clouds across
all terminals during this TAF period. There will be mountain wave
turbulence during the majority of this TAF period. -IG

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

&&

.PREV DISCUSSION...
/ISSUED 200 PM MDT Sun Apr 21 2024/

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

&&

.PRELIMINARY POINT TEMPS/POPS...
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

&&

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

&&

$$

http://www.weather.gov/greatfalls