A very strong upper low and trough moved out of the Great Basin area northeast across Wyoming during this time period. At the same time, a surface low moved across Wyoming into South Dakota.
Every event with a place to put it; 2 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 very strong upper low and trough moved out of the Great Basin area northeast across Wyoming during this time period. At the same time, a surface low moved across Wyoming into South Dakota. As a result of all the above, a deep, easterly upslope flow was in place across the Big Horn Mountains and adjacent foothills. During the first 24 to 36 hours of the event, conditions were unstable with steep lapse rates. This resulted in periods of heavy snowfall during the evening and overnight hours of the 24th and through the day on the 25th.
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 Mar 24, 2:36 AM MST, 9 hours 24 minutes earlier.
Area Forecast Discussion
National Weather Service Billings MT
336 AM MDT Fri Mar 24 2023
.DISCUSSION...
Today through Saturday night...
Confidence continues to increase for a significant snow event for
our foothills and mountains, starting later today and tonight.
Outside of some snow showers over the southern mountains this
morning, mainly dry and warm conditions can be expected across
much of the area through the day with temperatures reaching the
40s to lower 50s. Snow showers begin to spread into western areas
and increase over the mountains later this afternoon as a Pacific
wave drops through Idaho, pulling north to northeast upslope winds
and cooler temperatures in from the north over the area. As ascent
increases aloft, and near the surface with upslope winds, so does
the instability. Low and mid-level lapse rates increase towards 9
degrees C/km this afternoon. There is also CAPE of 100-200 J/kg
forecast over central and southern portions of the area this
afternoon and evening. Expect intense snow showers (could be
initially a rain/snow mix for some areas) to spread east into
central areas, down into the Sheridan foothills during the
evening. Latest hi-res guidance indicates a high chance (60-90%) for
snow rates of an inch or higher at times this evening, for areas
along and south of I-90. Given the instability, a few rumbles of
thunder are not out of the question as well. Snow will become more
widespread overnight, becoming focused along the foothills and
mountains into Saturday, before gradually lightening up Saturday
night. However, additional snow is expected Sunday into Monday as
another shortwave drops into the region from the northwest. More
information for the Sunday-Monday period can be found in the long
term discussion. Temperatures will be significantly cooler on
Saturday, with temperatures rising only into the 30s for most
locations.
With regards to snow accumulations through Saturday night,
confidence remains very high for the foothills and mountains to
receive several inches of snow. In fact, the mountains could see
anywhere from 1 to 2 feet, greatest on north and northeast-
facing slopes. Some of the more favored upslope areas could see
totals even approach 3 feet. As far as the foothills, totals will
approach 1 to 2 feet, especially for the Beartooth and Red Lodge
foothills. Latest NBM probabilities for a foot or more of snow are
at 60% for Red Lodge, with similar probabilities for Nye. Other
areas along or south of I-90 outside of the mountains could see
totals up to a foot. Lesser totals will be found to the north and
east of I-90. With this being a spring storm, the higher sun angle
will keep surfaces warmer than in the heart of winter. Road
surfaces aren't expected to drop at or below freezing until late
tonight, and even with the colder temperatures moving in, they
will likely return to above freezing for much of the day on
Saturday. Hence, much of the snow that occurs on lower albedo
surfaces (roads, sidewalks, etc) may see their snow melting very
fast, even as it falls. Vehicles and grassy surfaces have the
highest chance of accumulating snow to the forecasted amounts.
Impacts will still be high for this event, even with rapid
melting of the snow. Wet road surfaces during the day will freeze
at night all through the weekend, and rapid, sudden drops in
visibility are possible with strong snow showers and blowing snow.
Winter Storm Warnings and Winter Weather Advisories go into effect
for much of the western and central areas this afternoon. Travel
will be hazardous this weekend, so take the necessary precautions
if commuting.
HYDROLOGY...
Ice jam impacts persist along the Powder River. Those living near
rivers or streams should pay close attention to the state of the
ice over the next week or two. Move any equipment or livestock
away from low lying areas adjacent to rivers or streams. Take
protective action for any threatened structures. Be prepared to
seek the safety of higher ground should waters rise.
STP
Sunday through Friday...
By Sunday, a weak upper low will traverse over Wyoming through
the weak flow aloft bringing another shot for snow across our
region. Uncertainty remains in the extent of these snow showers
because of the weak flow aloft, but right now it looks like snow
showers will continue over the mountains and redevelop over the
lower elevations on Sunday through Monday afternoon. For lower
elevations, the best chance (80-90%) for snow showers during this
time will be around Billings to Sheridan and west once again,
however snow showers could fill in as far east as Miles City and
Baker (30-40% chance) bringing snow to much of the region. By
Monday afternoon, weak ridging will begin to build back in over
our region as surface winds turn southerly, ending any remaining
snow showers lingering over our region.
Additional accumulations during this time will be lighter than
the first half of the weekend, however areas farther east in lower
elevations could see snow that missed out early this weekend.
Even with high temperatures only in the 20s to 30s across the
region, snow accumulations will mainly be focused to grassy
surfaces and areas where new snow is present. The mountains have a
70-80% chance for an additional 4 inches, and lower elevations
around Billings to Sheridan and west have a 50-70% chance for an
additional 2 inches of snow. The Miles City area only has a 10-20%
chance for 2 inches.
Looking ahead to mid-week, there may be another chance for snow
moving in across our region Wendesday and Thursday with below
normal temperatures continuing. Arends
&&
.AVIATION...
VFR conditions will prevail during the morning hours before
conditions deteriorate this afternoon from snow and low ceilings.
KLVM will see the first impacts this afternoon (vicinity around
20z) before snow showers spread east to KBIL (around 00z) & KSHR
(around 04z) this evening. Portions of these snow showers will be
heavy, with very low horizontal and vertical visibility (VLIFR).
Expect widespread IFR/LIFR conditions. Uncertainty remains if the
heaviest snow will reach KBIL, but expect the worst conditions
from KBIL/KSHR west. Mountains obscurations will begin this
morning, increasing dramatically by the afternoon. Arends
&&
.PRELIMINARY POINT TEMP/POPS...
Tdy Sat Sun Mon Tue Wed Thu
-------------------------------------------------------
BIL 050 028/035 026/035 022/033 016/037 018/036 022/038
2/T 76/S 46/S 63/S 01/B 34/S 32/S
LVM 042 025/033 022/033 020/034 016/038 018/037 022/040
7/T 99/S 67/S 62/S 12/S 45/S 33/S
HDN 051 024/036 022/038 020/034 013/041 015/041 019/040
2/T 65/S 45/S 63/S 00/B 34/S 43/S
MLS 047 023/035 021/039 021/031 018/038 016/039 022/039
0/B 11/E 12/S 32/S 00/B 23/S 32/S
4BQ 050 025/036 023/039 022/033 018/041 019/042 024/041
0/B 22/S 23/S 43/S 00/B 13/S 32/S
BHK 043 016/031 013/034 015/026 011/033 012/034 017/037
0/U 10/E 01/B 32/S 00/B 13/S 33/S
SHR 043 021/030 017/030 015/029 008/034 013/036 018/035
3/T 87/S 67/S 64/S 00/B 23/S 43/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect from 6 PM this evening to noon
MDT Monday FOR ZONES 34-40-64-65-139-141-170-172.
Winter Weather Advisory in effect from 6 PM this evening to
noon MDT Monday FOR ZONES 42-57-58-63-228-235.
Winter Storm Warning in effect from 3 PM this afternoon to 6
PM MDT Monday FOR ZONES 56-66.
Winter Storm Warning in effect from noon today to noon MDT
Monday FOR ZONES 67-68-171.
Winter Storm Warning in effect from 6 PM this evening to 6 PM
MDT Monday FOR ZONES 138-169.
WY...Winter Storm Warning in effect from noon today to noon MDT
Monday FOR ZONE 198.
Winter Storm Warning in effect from 6 PM this evening to 6 PM
MDT Monday FOR ZONE 199.
&&
weather.gov/billingsThe national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
The mountains received 1 to 2 feet of new snow.
Snowfall of at least 6 inches was reported across the area. Interstate 90 from Sheridan to Buffalo closed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2023Every state in 2023This day in weather historyWarnings in Wyoming, March 2023
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: 1079782, 1079783.