065
FXUS65 KBYZ 261613
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
1013 AM MDT Sat Apr 26 2025

.KEY MESSAGES...

- Warmer Saturday and 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 (30-60 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.

- Warmer and drier mid week into next weekend.

&&

.UPDATE...

Stratus was slowly eroding over southeast MT this morning, with
patchy valley fog dissipating. Warm temperatures can be expected
today with highs in the 60s to lower 70s. A weak wave lifting
north in southwest flow will bring isolated to scattered showers
and thunderstorms to western and central areas later this
afternoon and evening. Have expanded isolated shower and
thunderstorm chances into central zones based on latest hi-res
guidance. The rest of the forecast remains in good shape. STP

&&

.DISCUSSION...

Today through Monday afternoon...

Southwesterly flow currently in place, thanks to a low off the
coast of California, will persist through the first half of the
day tomorrow, keeping conditions warm and mostly dry. There is a
slight chance (20-30%) for some showers along the western
foothills this afternoon, otherwise most of the region will remain
dry with high temperatures in the 60s to low 70s. Into Sunday,
highs will range from the mid 60s out west to the upper 70s in SE
MT. Showers associated the low moving into WY will begin in the
west mid afternoon Sunday. Instability (Sfc CAPE~500-1000 J/kg)
from daytime heating as well as above average atmospheric moisture
and shear (30-40 kts) will support thunderstorms with the
potential for a few strong ones. With snow levels around 9000 ft,
the first part of this event poses a risk for rain on snow,
especially under a thunderstorm capable of producing heavy rain.
Late evening and overnight, snow levels will drop to around
6-7,000ft, allowing for the transition to snow above these
elevations. Northerly flow will favor the north facing slopes for
this event with about 1-2 feet of snow forecasted in the
Beartooth/Absarokas. Early Monday morning, snowfall will begin to
impact the Pryors and Bighorns, with 10-14 inches expected for
the highest peaks. With regards to rainfall for the lower
elevations, the best chances of getting at least an inch of precip
is for south-central and far SE MT as well as Sheridan Co, WY at
30-60%. The best chances of of 1.5 inches of water are over the
northeast facing slopes and foothills of the Beartooth/Absarokas
as well as the NE facing slopes of the Bighorns and Pryors.

One thing to note with the above average temperatures is the
risk for snowmelt along the mid elevations. This along with the
heavy rain will cause rises in small streams. If you have any
interests near streams, now is the time to take the necessary
precautions. Additionally, any rain that falls over still frozen
ground or burn scars are at an increased risk for flash flooding.
Anyone, especially those near these areas, should use caution
during this time and make sure you have a way to stay up to date
with updates to the forecast.

As the low transitions east through the day Monday, precipitation
will gradually taper off through the day. Cool and breezy
conditions will be in place with high temperatures in the upper
40s and low 50s. A majority of the region has a 40-60% chance of
seeing gusts of at least 40 mph. Areas near the MT/WY border have
around a 30-50% chance of getting gusts to 50 mph. TS

Tuesday through Saturday...

Rising heights Monday night into Tuesday will usher precipitation
to the east and bring warm and dry conditions to the forecast area
Tuesday afternoon. Expect high temperatures in the 60s to near 70
in a few locations.

Another Pacific trof, this one moving quicker than the previous,
drops into the area Tuesday night into Wednesday for a quick shot
of precipitation. Given the temperature profile can`t rule out an
isolated thunderstorm or two during this period. Precipitation
potential looks mainly under a tenth of an inch, with a bit higher
in the mountains and foothills.

Amplified ridge works into the area for Thursday through the
weekend for mainly dry conditions with above normal temperatures.

Hydrology...issued a Hydrologic Statement covering the late
weekend early week precipitation event. Bottom line rain on snow
could bring rapid rises on creeks and streams in the foothills,
and flooding is not out of the question. May need some flood
watches for foothills areas with subsequent forecast packages.
Chambers

&&

.AVIATION...

Low stratus producing MVFR conditions over the far east including
KMLS and KBHK will gradually diminish through the morning.
Otherwise, VFR is expected to prevail through the period with
isolated to scattered showers and thunderstorms possible over
western and central areas, including KLVM and KBIL this afternoon
and evening. STP

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sun     Mon     Tue     Wed     Thu     Fri
-------------------------------------------------------
BIL 071 045/072 044/055 037/068 046/064 043/069 045/077
    2/T 26/T    +8/W    11/B    44/W    21/U    00/U
LVM 069 041/066 040/053 037/063 040/060 038/069 043/074
    2/T 19/T    +7/W    12/W    54/W    11/U    00/U
HDN 072 043/075 042/055 035/069 045/064 040/069 043/078
    0/B 15/T    +9/W    11/B    55/W    21/U    00/U
MLS 071 043/077 045/055 035/068 046/064 042/068 043/077
    0/B 02/W    97/W    00/B    53/W    21/U    00/U
4BQ 072 045/078 045/053 035/066 046/061 042/065 042/074
    0/B 12/W    89/T    10/U    34/W    11/U    00/U
BHK 065 040/075 042/053 029/065 042/063 037/064 037/072
    1/N 12/W    88/W    10/U    23/W    11/U    00/U
SHR 069 041/073 038/050 029/066 040/059 035/065 038/074
    1/B 02/W    8+/W    10/U    46/W    21/U    00/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch in effect from Sunday evening through
      Monday afternoon FOR ZONES 67-68.
WY...None.

&&

$$
weather.gov/billings