411
FXUS65 KTFX 201747
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1150 AM MDT Mon May 20 2024

Aviation Section

.SYNOPSIS...
Today, low elevation rain, and some mountain rain snow impacts our
region. Temperatures warm today and tomorrow, before cooling, mid
week. Afternoon and evening thunderstorms develop and move across
portions of north central, central and southwest Montana, for the
next few days. An active weather pattern favors periods of rain
snow, through the week.

&&

.UPDATE...
High temperatures and hourly temperatures across the plains of North-
central and Central Montana were increased to better reflect current
observations and trends. Sky grids were adjusted to better match
satellite trends. PoP and QPF across Southwestern Montana were
adjusted to better reflect current observations and trends. The rest
of the forecast is on track. Fog in the Browning area will gradually
clear within the next hour. Snow and rain showers will continue
across Southwestern Montana today. -IG

&&

.AVIATION...
20/18Z TAF Period

Expect showers/thunderstorms to move through the CWA this
afternoon/evening. The stronger storms could produce some pea size
hail. The airmass becomes stable this evening, thus the thunderstorm
activity will diminish a bit. However, expect another round of
showers/thunderstorms to redevelop by Tuesday afternoon.
Mountains/passes will be obscured at times today by passing storms.
Brusda

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

&&

.HYDROLOGY...
A flood watch has been issued for the Kings Hill, Monarch and
Neihart areas from Wednesday night into Friday. There is a 50
percent chance of 1 inch of liquid from this event in this area.
There is a 10 percent chance of 2 inches of liquid. Some of the
precipitation will fall as snow, especially for elevations above
7000 feet, which will help, but for areas lower than 7000 feet,
impacts could develop fairly quickly given how saturated the soil is
and how full the creeks/streams are currently in this region.

At this time, other areas of North Central and Southwest MT should
be able to handle the expected rainfall, but there is the
potential that additional flood statements might be needed. Brusda

&&

.PREV DISCUSSION...
/ISSUED 549 AM MDT Mon May 20 2024/

Note: The forecast area for the National Weather Service Great
Falls Weather Forecast Office includes, north central, central and
southwest, Montana.

Today...Temperatures are on a gentle warming trend. An upper
level trof progresses across the region. Low elevation rain and
some mountain rain/snow impacts the region. The greatest amount of
impactful snow accumulation is forecast to occur across Raynolds
Pass and US 191 near Big Sky, where there is a 70% chance of up to
3 inches of snow accumulation. Considering that we`re approaching
the end of May, and people, especially those who may be visitors
to The Treasure State, may be surprised to encounter some slushy
and slippery stretches of roadway, I`ve issued a Public
Information Statement for this area. Generally, any snow that
falls is wet and heavy and falling on mostly warm road surface
temperatures. Thunderstorm activity is forecast to develop and
move across the region. The greatest impact from these storms is
forecast to be strong and erratic gusty winds.

Tuesday through next Monday...A weak upper level ridge enters the
region, Tuesday, and low elevation high temperatures are forecast
to range around normal, with highs ranging from the upper 50s to
the mid to upper 60s. General afternoon and evening thunderstorms
develop and pass through our region into the mid week period. For
the remainder of this forecast period, periods of low elevation
rain and mountain rain/snow are forecast. The greatest impacts are
forecast to occur mid week, when there is a 40% to 70% chance that
some of our mountains will receive 4 to 9 inches of snow at and
above pass level, during the 24 hour period from Wednesday evening
through Thursday afternoon. For this reason, I`ve issued Winter
Weather Watches for these areas. We continue to monitor and will
adjust Watches, Warnings and Advisories, as is appropriate. As the
week progresses, the active weather pattern continues, with daily
periods of precipitation forecast. Please, see the HYDROLOGY section
below for more information in reference to potential flooding
impacts.
- Fogleman

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  35  64  41 /  30  20  30  10
CTB  59  34  62  40 /  60  30  30  10
HLN  60  39  66  43 /  50  30  30  10
BZN  55  32  61  37 /  60  40  40  10
WYS  50  28  52  29 /  60  50  50  20
DLN  53  32  59  38 /  50  40  20  10
HVR  61  37  64  41 /  30  20  20  20
LWT  55  32  59  37 /  60  20  50  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Wednesday evening through Thursday
morning for Elkhorn and Boulder Mountains-Northwest Beaverhead
County-Ruby Mountains and Southern Beaverhead Mountains-Southern
Rocky Mountain Front.

Flood Watch from Wednesday evening through Friday morning for
Little Belt and Highwood Mountains.

Winter Storm Watch from Wednesday evening through Thursday
afternoon for Gallatin and Madison County Mountains and
Centennial Mountains.

&&

$$

http://www.weather.gov/greatfalls