A late season, spring winter storm occurred over the mountains.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BYZ wrote it up.
A late season, spring winter storm occurred over the mountains.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Billings, MT wrote its last area forecast discussion before the first event at May 4, 10:39 PM MST, 2 hours 21 minutes earlier. Its key messages:
Area Forecast Discussion...Updated
National Weather Service Billings MT
1139 PM MDT Sun May 4 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms over the mountains and
western foothills this evening and overnight as a cold front
drops into the area.
- Cool and wet conditions later tonight through Tuesday. Several
inches of snow possible in the mountains. Wet snowfall
accumulations on grassy surfaces in the foothills.
- Drier and warmer conditions will return for the second half of
the work week.
&&
.UPDATE...
With increasing confidence for a period of heavy snow on northeast
aspects of the Beartooth-Absarokas, have issued a Winter Storm
Warning for our southwest mountains from midnight tonight to noon
Tuesday. Heavy snow will impact snow removal operations on the
Beartooth Highway.
Otherwise, scattered showers & t-storms are focused in 3 areas
early this evening: in our far west (as expected closer to main
trof axis), S-SE of Billings (developed off the Pryors & Wolf
Mtns), and in the far east close to the Dakotas border (along axis
of 850mb frontogenesis). Have adjusted evening pops/wx to account
for the current activity. None of the storms will be severe, or
even close to severe, but small hail is a good bet. Other than the
evening convection, the better chance of precip emerges overnight
in our west, along mid level baroclinic zone and aided by
easterly upslope winds. Cold advection is increasing over our
northwest and temps have fallen to the 50s at Judith Gap and
Harlowton, and 60s at Big Timber and Harlowton. The changing of
the air masses is underway. JKL
&&
.DISCUSSION...
Rest of Today through Tuesday night...
Ahead of an approaching cold front and trough, showers and weak
thunderstorms will be possible mainly west of Billings through
this evening. East of Billings, expect warm dry and breezy
conditions will persist for the rest of the day. The strongest
thunderstorms will be capable of producing small hail and gusty
winds.
Frontal passage will swing across the area tonight, passing
through the far east early Monday morning. The chance for
precipitation will slowly increase from west to east as the upper
trough begins to phase with an upper low near the Four Corners.
Widespread rainfall is forecast (greater than 60%) along with
mountain and foothill snow Monday through Tuesday. Total liquid
precip amounts range from a tenth of an inch in the northern areas
to more than an inch in the mountains. Storm total snow amounts
range from 6-12 inches, in the Absaroka/Beartooths and 6-10 inches
in the Bighorns. Adverse conditions will exist for those
recreating in the high country as well as travel along Highway 14
in the Bighorns. Uncertainty remains with foothill snow amounts,
though the current forecast has 2-4 inches for Red Lodge and 1-3
inches around Story. Winter weather highlights may be needed for
the mountains and foothills, continue monitoring the forecast for
changes.
Snow levels are expected to start off near 10,000 feet this
evening, dropping to 6,000 feet on Monday, and dropping towards
5,000 feet Monday night into Tuesday. The majority of the
precipitation looks to fall Monday afternoon into Tuesday morning,
when snow levels are falling. Temperatures in the foothills will
fall into the low 30s Monday night, allowing for precipitation to
transition to snow. Highs on Tuesday will range from the 40s to
50s. The chance for precipitation will diminish through the day
Tuesday as an upper ridge begins to build over the region.
PM/STP
Wednesday through Sunday...
Models continue to be in agreement that ridging/anti-cyclonic
flow will prevail at mid-week over our region in a light W/SW mid
level flow. This will allow for a daily chance of late day
showers across the CWA Thu-Sun, mainly over the higher terrain
and east of Billings (further away from any downslope effects).
The best chance of measurable rain overall is Thursday/Thu
evening. Cannot rule out some isolated thunderstorms as well with
modest MUCAPE (300-600 J/Kg) at times through next weekend. None
of this looks like anything terribly substantial as PWATs remain
under 0.50-0.70 inches through the extended period. Mainly
isolated to scattered spring-time showers/thundershowers.
Look for highs to be above normal through the period with readings
in the lower 70 Wednesday, mid to upper 70s Thursday and in the
lower 80s for next weekend. BT
&&
.AVIATION...
06z Discussion...
SHRA continue to move through the forecast area impacting all
locations with higher coverage in the foothills, including KLVM.
TSRA have all diminished and are not expected to return. Over the
coming hours RA will fill into the western foothills including
KLVM, K6SO, ect before progressing eastwards through the entirety
of the forecast area. Additionally, CIGs will begin to rapidly
drop to IFR across south central Montana and Northern Wyoming,
while areas further east, such as KMLS, should only see MVFR
conditions in this TAF period. After 00z, snow/freezing levels
will drop and thus RASN was included in the TAF for KLVM and
KSHR, however, all sites where the terminal sits at 4,000ft MSL or
higher could see some snow mix in.
Winds will also be gusty with a primarily northerly component for
most of the period. Sustained winds between 15-20kts with gusts
up to 30kts looks to linger through at least 00z area-wide.
Mountains will be obscured throughout the period. WMR
&&
.PRELIMINARY POINT TEMP/POPS...
Tdy Mon Tue Wed Thu Fri Sat
-------------------------------------------------------
BIL 080 046/051 038/050 037/071 050/079 050/075 050/082
0/U 39/R 86/R 10/U 02/T 31/U 01/U
LVM 072 039/046 032/049 033/069 044/075 044/074 047/079
4/T 89/R 75/O 10/U 02/T 21/U 12/T
HDN 082 045/054 037/051 037/072 045/079 049/076 049/083
2/T 29/R 98/R 10/U 02/T 31/U 11/U
MLS 083 050/060 040/054 041/072 050/080 052/076 049/083
0/U 24/R 76/R 10/B 01/U 21/U 11/U
4BQ 082 050/061 039/050 042/068 049/077 050/074 049/080
2/T 23/R 97/R 21/B 01/U 21/U 00/U
BHK 085 048/066 038/054 038/069 047/077 047/074 045/078
0/U 33/R 76/R 10/B 01/U 21/U 01/U
SHR 079 045/053 033/047 034/067 041/075 045/073 045/079
2/T 28/R 99/R 31/B 02/T 22/T 11/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until noon MDT Tuesday FOR
ZONE 67.
WY...None.
&&
weather.gov/billingsThe national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
Inch of wse at Placer Basin and Cole Creek with temps in the 20s as of 1am on 5/6.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2025Every state in 2025This day in weather historyWarnings in Montana, May 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1268701.