676
FXUS65 KBYZ 262151
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
351 PM MDT Sat Apr 26 2025

.KEY MESSAGES...

- Warmer through Sunday (60s and 70s).

- Scattered showers over the western foothills this afternoon and
  evening (10 to 30 percent chance).

- A spring storm system Sunday and Monday could produce
  significant precip across much of the area (30-70 percent
  chance of at least 1 inch of rain / snow water equivalent).

- Foothills flooding due to rain falling on and melting snowpack
  is possible late Sunday through Monday, including areas
  downstream of the Robertson Draw, American Fork, and Elk burn
  areas.

- Chance for showers returns late Tuesday before a warm and dry
  end of the week.

&&

.DISCUSSION...

Through Sunday night...

A weak wave lifting through the region in southwest flow was
bringing a few showers and thunderstorms to western areas this
afternoon. Expect isolated to scattered showers and thunderstorms
to continue to advect through western and central areas into the
evening hours. Stratus and fog are expected to form over the far
east tonight, reducing visibility at times.

Heading into Sunday, temperatures will warm into the 60s and 70s,
with some areas approaching 80 degrees over the east, ahead of a
large upper low over the Great Basin that will lift north and east
into Monday. Energy advecting in from the southwest, moisture
moving in from the south and east, and low level north to east
upslope flow are expected to combine and allow showers and
thunderstorms to develop over western and central areas during the
afternoon. A surface low centered over southeast MT/northeast
Wyoming will be the focus for a few strong to possibly severe
thunderstorms late in the afternoon on Sunday into Sunday evening
for areas generally north and east of a Hardin to Broadus to
Alzada line. MUCAPE values of 500-1000 J/kg, deep layer shear of
30-45 kts, and PWATs approaching .75 inches of water should
support a wind and hail threat, along with heavy rainfall with any
thunderstorm.

As cold air advection/frontogenesis works in from the north
Sunday evening, precipitation is expected to become widespread
and heavy at times over the area, shifting south and settling
into the mountains and foothills late Sunday night into Monday
morning. Snow levels will start off near 9,000 ft, dropping
towards 6,000 ft by Monday morning, with the potential for snow
levels to drop even lower over portions of the western foothills.
For precipitation totals, both snow and rain for the event, more
information can be found in the long term discussion as well as on
our website. Given the heavy precipitation potential, rain on
snow, and concerns about burn scar flooding, flood watches have
been issued Sunday into Monday for portions of the area. For
specifics on precipitation and flooding concerns, please visit
our website.

STP


Monday through Saturday...

Monday morning will feature the bulk of the precipitation for this
event. A f-gen band will push through the entire CWA from NW to SE
through the morning with high QPF values (near 1" for some
locations) which will give the western 2/3 of the CWA chances for
good soaking rainfall Monday morning. Snow levels by this time
should have already rapidly dropped to near 6,000ft for most
locations as they continue to gradually lower throughout the
event. Concerns remain for burn scar flooding on recent fires, but
there is some uncertainty regarding dropping snow levels and how
much rain versus snow falls on the scars. The bigger flooding
concern will be along the foothills of the Beartooth/Absarokas and
the creaks and streams that flow out of the range. With these
waterways already running high following some mid-level snowmelt,
it should not take much to fill up the creeks. With the 1.5"+ of
rainfall possible in the foothills here, some minor flooding is
possible. Additionally, low lying areas could see some ponding or
minor flooding as a result too. Precipitation totals in these
areas of concern will likely exceed 2" with widespread 1" totals
for the southern 2/3 of the CWA and all foothills locations.
Mountain snow totals will be equally impressive, the highest
elevations near Mystic Lake and Granite Peak could be over 3 feet
of snow. Widespread 1ft+ is likely throughout the Bighorns.

Precipitation should be rapidly ending from west to east by
Monday afternoon and be completely out of the region by early
Tuesday morning. As the f-gen band moves through far southeast
Montana a quick inch of rain could fall in areas in and around
Carter Co. Flooding is not a concern here, but this could help
relieve some drought conditions.

The next chance for precip will come late Tuesday into early
Wednesday as a quick moving shortwave drops in from the northwest.
Some showers with a widely isolated thunderstorm are possible
Tuesday afternoon and Wednesday afternoon with a quick tenth of an
inch of precip under any one of these showers.

After that shortwave exits to the east, there is great consensus
in a building ridge towards the end of the week. Temperatures have
continued to trend upwards during this period. Low 80s are now
possible near and east of Billings for Friday and Saturday. There
should be minimal fire concern as this will come on the heels of
a soaking rain event and RH values should be above 25%. WMR

&&

.AVIATION...

In general, VFR is expected to prevail through the period for most
areas. Isolated to scattered showers and thunderstorms are
possible over western and central areas, including KLVM and KBIL
this afternoon and evening. Localized reductions to MVFR are
possible with the shower/thunderstorm activity. Low stratus and
patchy fog are expected to develop over the far east tonight into
Sunday morning. STP

&&

.PRELIMINARY POINT TEMP/POPS...

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 045/072 041/054 038/067 047/064 043/070 046/078 049/078
    23/T    +8/W    01/U    63/W    20/U    00/U    12/W
LVM 038/065 037/052 035/062 039/060 038/068 042/075 046/072
    18/T    +8/W    02/W    63/W    20/U    01/U    14/W
HDN 039/076 041/054 032/069 045/064 041/069 043/079 046/080
    13/T    +9/W    10/U    75/W    20/U    00/U    12/W
MLS 041/077 044/055 033/069 047/066 043/067 041/079 048/081
    02/T    97/W    00/U    63/W    20/U    00/U    11/U
4BQ 041/079 044/053 033/067 047/062 042/065 042/076 047/078
    12/T    7+/T    20/U    63/W    20/U    00/U    01/U
BHK 038/076 041/052 028/066 042/063 038/064 036/072 042/075
    12/T    98/T    20/U    33/W    20/U    00/U    01/U
SHR 041/075 037/049 029/065 041/059 036/065 038/075 042/076
    02/T    6+/W    30/U    66/W    21/U    00/U    12/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch in effect from Sunday afternoon through Monday
      afternoon FOR ZONES 34-40-56-64>68-139-141-170-172.
     Winter Storm Warning in effect from 6 PM Sunday to 6 PM MDT
      Monday FOR ZONES 67-68.
     Flood Watch in effect from Sunday evening through Monday
      evening FOR ZONES 138-169-171.
     Winter Storm Watch in effect from Monday morning through
      Monday evening FOR ZONE 171.
WY...Flood Watch in effect from Sunday evening through Monday
      evening FOR ZONES 198-199.
     Winter Storm Watch in effect from Monday morning through
      Monday evening FOR ZONE 198.

&&

$$
weather.gov/billings