A strong upper low over Idaho combined with a surface low over central Wyoming brought a late season heavy snow event to the Sheridan Foothills area. Tight surface pressure gradients associated with the surface low resulted in gusty northwest winds and considerable blowing and drifting snow.
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 strong upper low over Idaho combined with a surface low over central Wyoming brought a late season heavy snow event to the Sheridan Foothills area. Tight surface pressure gradients associated with the surface low resulted in gusty northwest winds and considerable blowing and drifting snow.
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 Apr 2, 2:02 AM MST, 3 hours 58 minutes earlier.
Area Forecast Discussion
National Weather Service Billings MT
302 AM MDT Mon Apr 2 2018
.SHORT TERM...valid for Tdy and Tue...
Deep upper trough was digging into the Pacific Northwest this
morning. Strong diffluent flow was present on the front side of
the trough, shifting into northern Idaho and western Montana.
Weaker diffluent flow has spread as far east as southern Montana,
and started the initial round of snow over the forecast area. In
addition, one jet max was working out ahead of the trough, while a
second max was rounding the trough. These two maxes will be in
place for coupled jet forcing today for strong ascent. Infrared
satellite image was tracking an area of cooling cloud tops moving
into the western part of the forecast area at the moment, This
area was in association with the parameters mentioned above and
will cause snow to increase in coverage and intensity early this
morning. Dynamic forcing will shift eastward through the day.
Cyclogenesis over Wyoming will serve to pull colder air in through
the day, and to tighten the surface pressure gradient, creating
areas of blowing snow.
Snow accumulations can be very difficult this time of year, as
the ground has been progressively warming over the last several
weeks, due stronger solar penetration with a higher sun angle. The
higher sun angle will play with accumulations during the day too,
even with snow going on (just harder to accumulate during the day
this time of year). That being said, believe dynamics are strong
enough that should see strong accumulations today, especially on
grassy surfaces and over higher hills. Will leave current
highlights in place. Snow amounts provided by inherited forecast
look good and will not adjust much. Will have to watch Sheridan
county today as winds could cause a bigger problem with blowing
snow than an Advisory covers. For now, will leave current
highlight in place, with a stronger worded forecast, and brief the
day crew to monitor closely.
Snow will taper off from west to east late this afternoon and
this evening, with lingering activity along the foothills. The
east will continue to see snow and blowing snow as the surface low
drops toward Kansas. Winds should die down tonight, so blowing
snow concerns will be limited to the evening hours the over
eastern zones.
Tuesday is looking like a mainly dry day as heights rise a bit in
northwest flow. Models were starting an over running snow event
Tuesday night, as moisture moves over cold air in place. Spread
PoPs farther east into central and eastern zones to account for
this activity. Should see warmer temperatures on Tuesday, but this
should be held in check by fresh snow cover. TWH
.LONG TERM...valid for Wed...Thu...Fri...Sat...Sun...
Unsettled pattern persists through the extended period. Pattern
remains fairly consistent, but timing of individual pieces of
energy remain problematic. Have attempted to maintain scattered
through the periods, with some higher pops in high terrain and
areas with some agreement on timing. Generally only made minor
tweaks to latest model run.
Unsettled northwest flow will persist through Saturday morning.
Plentiful Pacific moisture, and good upper level jet support,
combine with periodic weak shortwaves crossing the region to bring
potential for rain/snow showers through Saturday morning. Timing
of impulses continue to be an issue, but should see periods of
fairly widespread shower activity.
Ridging takes over Saturday, but clearing potential is short-
lived, as ridge appears somewhat dirty and quickly forced
eastward as the next trof begins push into the region. This next
large weather system will move in Saturday night Sunday morning.
At this time this system should bring another shot of cold air
and rain/snow across the region Sunday and into Monday.
As for temps, expect to see below normal highs and lows. The
warmest day of the period looks like Saturday, under a short
period of ridging, where 50s will creep back into westernmost
plains, while 30s persist in the east. AAG
&&
.AVIATION...
Expect widespread IFR or lower, with accumulating snowfall
through today. Mountains will remain obscured. Northerly winds
will increase Monday afternoon causing additional visibility
restrictions in blowing snow, especially from KBIL eastward. AAG
&&
.PRELIMINARY POINT TEMP/POPS...
Tdy Tue Wed Thu Fri Sat Sun
-------------------------------------------------------
BIL 028 013/037 023/043 028/036 024/038 027/048 033/047
+/S 51/B 33/O 44/O 64/O 33/O 44/R
LVM 031 017/041 026/048 031/045 028/047 032/053 033/051
+/S 43/O 35/O 56/O 75/O 44/O 54/R
HDN 031 008/037 019/042 025/038 021/039 024/047 032/046
+/S 81/B 33/O 54/O 65/S 33/O 44/O
MLS 028 010/029 014/037 022/032 018/033 022/041 029/041
+/S +1/B 22/S 43/S 43/S 32/S 43/S
4BQ 034 013/033 019/042 025/037 019/036 023/046 031/045
+/S +1/E 12/R 44/O 54/S 32/O 43/O
BHK 027 008/026 010/036 019/030 013/029 018/039 026/039
+/S +2/S 21/B 33/S 33/S 32/S 43/S
SHR 036 013/037 020/046 026/044 025/044 028/053 033/050
9/S 82/S 22/O 34/O 55/O 32/O 34/R
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until midnight MDT tonight FOR
ZONES 28-29-34-35-39>42-56-63>68.
Winter Storm Warning in effect until 6 AM MDT Tuesday FOR
ZONES 30>33-36>38-57-58.
WY...Winter Weather Advisory in effect until 6 AM MDT Tuesday FOR
ZONES 98-99.
&&
weather.gov/billingsPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BILLINGS MT
547 AM MDT MON APR 02 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0533 AM HEAVY SNOW BIG TIMBER 45.83N 109.95W
04/02/2018 M6.0 INCH SWEET GRASS MT TRAINED SPOTTER
&&
TWH1 winter storm. Local standard time, as filed.
Wind gusts of 50 mph with significant blowing and drifting snow were reported. I-90 was closed south of Sheridan.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2018Every state in 2018This day in weather historyWarnings in Wyoming, April 2018
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: 746373.