636
FXUS65 KTFX 112040
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
240 PM MDT Sat May 11 2024

.SYNOPSIS...

The ongoing warm weekend will continue into Monday. Showers and a
few thunderstorms will develop along the Hi-Line tonight, with
additional afternoon and evening showers and thunderstorms likely
across the plains Sunday and Monday. A cooler and more unsettled
pattern will arrive for mid-week.

&&

.DISCUSSION...

Through Monday... Upper level ridging, with axis over the west
coast, is slowly building eastward. With ridge axis off to the west,
flow aloft is out of the northwest. A weak wave diving southeastward
through this flow will result in showers and a couple thunderstorms
tonight, mainly across eastern portions of the Hi-Line.  This
activity moves east of the area by 7AM Sunday.

Additional instability will develop across Central and North-central
Montana Sunday, resulting in a round of isolated afternoon and
evening showers and thunderstorms. Concerns with thunderstorms that
form will be for gusty winds, given relatively deep mixing and
inverted-V soundings.

Expect more of the same on Monday, though the opportunity for
showers and perhaps a thunderstorm or two will spread further
southwest into Southwest Montana. Additionally, breezy westerly
winds look to develop over the plains as a passing wave moves
overhead. -AM

Tuesday through next Saturday... Expect periods of rainfall to
continue through the day on Tuesday as moisture continues to work
into the area from the north and west. For the most part,
precipitation will be rainfall except at the highest elevations even
as cooler air from Canada pours into the region behind a surface
cold front that will work in with the rain.

Beyond Tuesday, a ridge will develop to our southwest, but with a
northwesterly flow aloft in place, expect near to perhaps a bit
cooler than average temperatures, with opportunities for showers.
Ludwig/AM

&&

.AVIATION...
1126 AM MDT Sat May 11 2024 (11/18Z TAF Period)

The main concern this TAF period will be for showers and perhaps a
thunderstorm or two across eastern portions of the Hi-Line (KHVR)
late tonight. Confidence in thunder at the KHVR terminal was too low
to mention in the TAF at this time. The only other concern will be
for lower clouds across the plains of North-central and Central
Montana tomorrow morning, though confidence in sub-VFR conditions
being realized is less than 40% a this time. -AM

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

&&

.HYDROLOGY...
A Flood Warning remains in effect for Clear Creek in North Central
Montana through this evening, with water levels expected to
slowly fall from minor flood stage to action stage tonight.
Additionally, a Flood Watch remains in effect for the nearby Bears
Paw Mountains through the weekend as warming temperatures and
subsequent snowmelt runoff, and remaining runoff from rainwater,
could push creeks and streams out of their banks. While some
rainfall is expected this evening, rainfall amounts should not be
high enough to significantly worsen any flooding of streams and
creeks.

Further south across the Island Ranges of Central Montana (i.e.
Highwood, Moccasin, Judith, Little Belt, and Snowy), increased
snowmelt and subsequent runoff into creeks and streams is expected
through Monday as overnight temperatures and dewpoint temperatures
remain above freezing. This runoff could result in waterways
nearing bankful by Saturday night/Sunday morning. Hence, a Flood
Watch has been issued for the Little Belts eastward toward the
Lewistown area. - Moldan/AM/Ludwig

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  78  49  76 /  20  20  10  20
CTB  47  78  49  73 /  20  20   0  20
HLN  50  80  51  77 /   0  10   0  20
BZN  43  76  46  73 /   0   0  10  50
WYS  35  69  37  65 /  10  10  10  60
DLN  42  76  46  73 /   0   0  10  30
HVR  48  76  49  80 /  50  10  30  30
LWT  45  70  46  71 /  20  30  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday morning for Bears Paw Mountains and
Southern Blaine.

Flood Watch through Monday morning for Cascade County below
5000ft-Fergus County below 4500ft-Judith Basin County and Judith
Gap-Little Belt and Highwood Mountains-Meagher County Valleys-
Snowy and Judith Mountains-Western and Central Chouteau County.

&&

$$

http://www.weather.gov/greatfalls