Winter Storm in Montana, April 27 to 28, 2025

Area Forecast Discussion
National Weather Service Billings MT
215 PM MDT Sun Apr 27 2025

.KEY MESSAGES...

- Scattered strong to severe thunderstorms expected this afternoon
  and evening, capable of producing heavy rain, strong winds and
  hail.

- Today and Monday's weather system producing significant precip,
  especially west and south of Billings with 1.5-3.5" expected.

- Foothills flooding due to rain falling on snow and melting
  snowpack is possible late today 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...
Rest of Today through Monday Night...

Low-level noise of moisture and clear skies have helped to
destabilize much of the area at and east of Billings, with CAPE
1000-1500 J/kg present across far southeast MT. A noticeable
dryline witha ~20 dewpoint difference in northern Campbell County
is also progged to move north into MT, and the combination of all
this basically matches up with the previously discussed severe
thunderstorm threat for this afternoon and evening. The main
threat is large hail at least a quarter in diameter, with a
secondary threat being gusts up to 60 mph and localized, heavy
rain. The timing of thunderstorms begins around 5PM and persists
through midnight before losing any lingering instability and
switching over to widespread rain/snow.

Part 2 of this upcoming weather system is the heavy rain
potential with it. THere is still a very high chance (90%) of
getting at least 0.5" of liquid precipitation across much of
south-central Montana, and a 25-40% of getting at least 1.5" of
liquid precipitation. The main area for concern is along the
Beartooth Foothills south of I-90 and into the mountains. On top
of a large amount of water, excessive runoff is likely occurring
at the same time due to very warm temperatures of this weekend.
While rain potential this evening is spotty due to its convective
nature, all folks should take action and move equipment and
livestock from low-lying areas. Some Burn Scars are at risk of
flash flooding as well, including the Robertson Draw, American
Fork, and Elk.

Rain will quickly transition to snow between midnight and 6am
over the foothills, with a quick decrease in snow amounts as you
head away from the mountains (for example, Red Lodge has 4-7" of
snow expected tomorrow morning, while Roberts is less than 1).
While measurable amounts to what's in the forecast will be
difficult (due to how fast it'll melt), the snow rates will still
be heavy, and the main concern from the snowfall will be drastic
reductions in visibility and slushy road conditions.

All in all, this is a very dynamic, spring system creating lots of
types of weather with a range of impacts. Have a plan in place if
you have outdoor plans into this evening, and prepare for all
types of flooding in low-lying areas across south-central Montana.

Vertz

Tuesday through Sunday...

Quick upper ridge quickly moves into eastern Montana on Tuesday,
allowing temperatures to jump back to the mid to upper 60s. It is
short lived though, as an upper trough pushes into the area
Tuesday night and lingers into Wednesday. Precipitation chances
increase to 40 to 70 percent late Tuesday night through much of
the day Wednesday. Precipitation chances should diminish quickly
Wednesday evening with drier northwest flow weakening instability
profiles. Cloud cover and showers will hold temperatures in the 55
to 65 degree range Wednesday.

Upper ridging takes hold Thursday into Saturday for dry and warm
conditions. Late in the day Saturday will begin to see the back
side of the ridge move in with stronger southwest flow pulling in
some Pacific moisture. Expect diurnal showers and thunderstorms
Saturday afternoon and evening over the western mountains and
foothills. Upper low moves into the Great Basin Sunday into
Monday. This system has potential to bring more widespread
impactful precipitation to the area. Current track is a bit south
for the best precipitation to be over our area, but some ensembles
are hinting at a more northerly track. Will have to keep an eye on
this through the week ahead. Chambers/Vertz

&&

.AVIATION...

18z Discussion...

VFR conditions are expected for most locations through 00z. Some
TSRA are forecast to pop around KBIL/KSHR around 21z but should be
limited in coverage before they move NE of the terminals. KMLS has
a greater chance of seeing a TS at the terminal between 00z and
04z. It is possible that a storm may come with some strong winds
or some GR.

After the TS threat ends, widespread precipitation fills in from
west to east. Widespread gradually lowering CIGs and VIS should
result in most sites seeing IFR to LIFR after 06z. Additionally,
breezy winds can be expected from the NNE gusting over 20kts
region wide. It is looking likely that KSHR/KLVM does switch over
to RASN or even -SN around 12z Monday morning. WMR
&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 041/046 037/067 045/061 041/067 044/077 047/079 050/072
    +9/W    01/B    86/T    10/B    00/U    01/U    34/W
LVM 036/048 035/062 038/056 036/066 041/074 045/074 046/063
    +8/W    03/W    86/T    10/U    00/U    13/W    46/W
HDN 039/046 033/069 044/060 038/067 041/077 045/081 049/075
    +9/W    00/B    97/T    11/B    00/U    01/U    34/W
MLS 044/049 034/070 046/061 039/067 042/076 047/082 052/077
    98/W    00/B    55/W    11/B    00/U    01/U    12/W
4BQ 044/050 034/067 046/057 038/063 041/074 046/080 052/075
    8+/W    20/U    35/T    11/B    00/U    01/U    13/W
BHK 041/050 030/066 042/059 035/063 037/072 043/076 047/073
    99/W    00/U    25/W    11/B    00/U    01/U    12/W
SHR 038/045 029/065 040/056 032/062 036/073 041/078 046/071
    8+/W    20/U    68/T    21/U    00/U    01/U    25/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch in effect through Monday afternoon FOR ZONES
      34-40-56-64>68-139-141-170-172.
     Winter Weather Advisory in effect from midnight tonight to 6
      PM MDT Monday FOR ZONES 56-66.
     Winter Storm Warning in effect from 6 PM this evening to 6 PM
      MDT Monday FOR ZONES 67-68.
     Flood Watch in effect from 9 PM MDT this evening through
      Monday evening FOR ZONES 138-169-171.
     Winter Storm Warning in effect from 9 PM this evening to
      midnight MDT Monday night FOR ZONE 171.
WY...Flood Watch in effect from 9 PM MDT this evening through
      Monday evening FOR ZONES 198-199.
     Winter Storm Warning in effect from 9 PM this evening to
      midnight MDT Monday night FOR ZONE 198.

&&

weather.gov/billings

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