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063
FXUS65 KTFX 190241
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
841 PM MDT Tue Jun 18 2024

.SYNOPSIS...

Although the remainder of the week will largely be unsettled,
temperatures will be on the warming trend. Mostly dry and warm
conditions this weekend will trend cooler early next week as breezy
westerly winds develop.

&&

.UPDATE...

-- Changed Discussion --
Showers and thunderstorms over Central/North-central MT are now
starting to diminish as diurnal heating wanes, but lighter shower
activity will linger through midnight or so. Lapse rates are
still sufficient for a few more storms over the southwest,
especially for locations south of I90. Light winds and abundant
surface moisture will create favorable conditions for patchy fog
development later tonight into early Wednesday, particularly for
areas that undergo partial clearing and have received rainfall
today; however, broad troughing aloft is expected to maintain at
scattered cloudiness and should ultimately reduced the overall
coverage. Pops and temperatures were matched per current trends
with the remainder of the forecast remaining on track. - RCG
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&&

.AVIATION...
19/00Z TAF Period

The loss of diurnal heating will result in decreasing shower and
thunderstorm activity, though broad troughing aloft will maintain
scattered lower VFR clouds for most locations during the overnight
hours and lighter end showers may persist over Central and North-
central MT through 19/06Z. Abundant surface moisture and lighter
winds may encourage patchy fog development for locations that
undergo partial clearing between 19/09 and 19/15Z. Colder air aloft
does remain over the region on Wednesday, but afternoon shower and
thunderstorm coverage will be much less than today. - RCG

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

&&

.PREV DISCUSSION...
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/ISSUED 247 PM MDT Tue Jun 18 2024/

Through Friday... Strong upper level ridging across the eastern
CONUS will allow for upper level troughing to persist across the
western CONUS this week. Embedded waves within this troughing will
bring the best chances for mainly afternoon and evening showers and
thunderstorms this afternoon and Friday afternoon, but will be
around Wednesday and Thursday as well. Temperatures will be on a
warming trend this week, though overnight lows tonight will
largely be in the 30`s F, with elevated valleys dropping into the
20`s. Temperatures tonight will challenge record lows for the date
in many locations.

One thing to keep an eye on will be for an opportunity for more
organized thunderstorms Friday afternoon. If the present timing
holds, the combination of the passing shortwave, ample instability,
and sufficient shear will result in a respectable environment for
stronger storms.

Saturday into next week... Flow across the eastern CONUS finally
becomes more zonal, allowing systems to begin tracking eastward
again. As troughing from this work-week shifts eastward, another
will begin moving eastward across the northern Pacific, setting up
near the Canadian coastline by Friday night. This will result in a
brief period of upper level ridging across the northern Rockies. Dry
conditions are forecast Saturday through at least early Sunday, with
temperatures Sunday climbing to the warmest of the forecast period.

The next round of troughing will begin building in by Sunday
afternoon. There is a fair bit of uncertainty at this range with
respect to timing and depth/strength of this troughing, which leads
to decreased confidence on potential impacts. A more benign scenario
would result in just a period of breezy westerly winds in the
afternoon Sunday, primarily across the plains, while a more
impactful scenario would bring showers and perhaps a few
thunderstorms as well later in the day. As of now the more benign
scenario is favored, but trends will need to be monitored for
timing changes with this system.

Regardless, temperatures trend closer to normal for Monday, with
breezy winds looking to continue over the plains into early next
week. Small opportunities for showers and thunderstorms will be
around early next week, but specifics are murky at this point. -AM
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&&

.PRELIMINARY POINT TEMPS/POPS...
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GTF  37  67  41  75 /  70  20   0  10
CTB  33  64  38  73 /  40  30   0  20
HLN  40  72  45  80 /  40  20   0  10
BZN  33  69  39  77 /  50   0   0  10
WYS  26  63  33  72 /  20   0   0  10
DLN  32  67  38  73 /  50   0   0   0
HVR  40  70  44  79 /  80  30  10  20
LWT  34  65  41  71 /  40  50   0  20
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&&

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

$$

http://www.weather.gov/greatfalls