991
FXUS65 KTFX 251507
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
907 AM MDT Sat May 25 2024

.SYNOPSIS...
It will be mostly cloudy today, with rain showers or a
thunderstorm developing over Southwest MT this morning, and then
moving northeast into Central MT this afternoon. Snow is possible
in the mountains, mostly above 7000 feet. The showers exit the
area on Sunday, with drier and warmer temperatures expected for
Monday and Tuesday. There will be another chance for storms
Tuesday afternoon and evening, some of which could be strong.

&&

.UPDATE...

Very minor changes made to the going forecast that mainly involved
blending in a little of the latest model guidance with the
previous forecast. Patchy fog was added near Bozeman for tonight.
Confidence is overall low (<20%), however, with departing showers
some of the convective allowing models showed some favoring for
fog/mist lingering around Gallatin Valley in the early morning
hours.

-thor

&&

.AVIATION...
25/12Z TAF Period

VFR conditions will prevail during this TAF period at all terminals
except for the KEKS and KHVR terminals. At the KHVR terminal there
has been very patchy fog for the past few hours. This is likely to
continue for the next 2 hours. The fog could briefly reduce
visibility to LIFR levels. At the KEKS terminal there will be MVFR
ceilings at the very end of this TAF period. The main concern for
this TAF period is rain showers and thunderstorms Saturday afternoon
and evening. At the KEKS, KBZN, KWYS terminals there is a 50% chance
for thunderstorms Saturday afternoon through very early Sunday
morning and so a PROB30 group was included for them in those TAFs.
At the KGTF and KHLN terminals late Saturday afternoon through very
early Saturday evening there is a 50% chance for thunderstorms and
so a PROB30 group was included for those TAFs. At the KHVR and KLWT
terminals late Saturday afternoon through Saturday evening there is
a 50% chance for thunderstorms and so a PROB30 group was included
for those TAFs.

At the KCTB terminal there is a 20% chance for rain showers Saturday
afternoon. At the KWYS, KEKS, KBZN, KHLN and KLWT terminals there
will be rain showers Saturday afternoon through the end of the TAF
period. At the KHVR and KGTF terminals there is a 50% chance for
rain showers Saturday afternoon and early evening. At the KHVR
terminal there is a 40% chance of rain showers Saturday afternoon.
At the KWYS terminal Saturday evening through very early Sunday
morning there is 40% chance for rain showers and so a PROB30 group
was included for this. At the very end of this TAF period there will
be low-level wind shear around the KCTB and KLWT terminals. Due to
the rain showers, mountain obscuration will occur intermittently
primarily across Southwestern Montana Saturday afternoon through the
end of the TAF period. -IG

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

&&

.PREV DISCUSSION...
/ISSUED 533 AM MDT Sat May 25 2024/
Today through Monday...Patchy morning fog will affect the Hi-line
area through about 10 AM this morning. Otherwise, an upper level
disturbance will move from southwest to northeast through the CWA
today. Expect rain/isolated thunderstorms to develop this morning
over Southwest MT and gradually spread northeastward through the
day today. Overall, rainfall amounts should be light, about 0.10
inches at lower elevations and around 0.20 inches in the
mountains. I will issue a SPS this morning, as precipitation
should be snow by tonight, mostly for elevations above 7000 feet
in the Big Sky area. The system will be slow to exit the area,
with some light showers lingering into Sunday. Monday is looking
mostly dry, as an upper level ridge starts to build over the CWA.
Slightly below afternoon temperatures are expected today and
Sunday, while temperatures will be warming up a bit above normal
by Monday. It will be windy at times on Sunday for areas
along/west of the I-15 corridor over North Central MT.

Tuesday through Saturday...An upper level ridge will be over the
area on Tuesday morning, which will quickly break down by Tuesday
afternoon, as an upper level trof approaches from the west.
Tuesday will likely be the warmest day over the next week, but I
did lower NBM guidance a few degrees for Tuesday afternoon, as it
might be too warm. Otherwise, the main concern Tuesday is for the
potential for severe storms Tuesday afternoon/evening. With the
flow aloft becoming southwest, it will be unstable by late
afternoon. However, it is not that unstable, thus the potential
for widespread severe storms looks low at this time. On
Wednesday, the main cold front moves though. Temperatures will
start to cool a bit, as well as the potential for heavy rainfall
over Central MT. Right now there is about a 30 percent chance for
locations between Great Falls and Lewistown to receive 0.50 inches
of rainfall. This would be convective rainfall, thus portions of
Central MT are in a marginal risk for excessive rainfall during
this period. It does remain unsettled for Thus/Fri with scattered
showers continuing and afternoon temperatures just a few degrees
below normal. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  64  41  62  39 /  50  30  10   0
CTB  63  40  60  39 /  30  10  10   0
HLN  65  42  64  43 /  60  20  10   0
BZN  63  36  62  36 /  70  80  10   0
WYS  54  33  54  30 /  70  70  20   0
DLN  60  35  62  36 /  70  40   0   0
HVR  69  44  65  43 /  40  40  30  10
LWT  62  37  58  37 /  70  60  20   0

&&

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

$$

http://www.weather.gov/greatfalls