A passing low pressure system and moist upslope flow produced periods of heavy snowfall over the Snowy Range.
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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 CYS wrote it up.
A passing low pressure system and moist upslope flow produced periods of heavy snowfall over the Snowy Range.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at Mar 31, 4:31 AM MST, 1 hour 29 minutes earlier.
Area Forecast Discussion
National Weather Service Cheyenne WY
531 AM MDT Sat Mar 31 2018
.SHORT TERM...(Today through Sunday Night)
Issued at 345 AM MDT Sat Mar 31 2018
Water vapor loop showed a potent upper level shortwave approaching
Wyoming from the northwest. Arctic cold front moved south through
the high plains, with winds shifting to the north and northeast, and
abundant low cloud cover. Most of the precipitation was falling well
north of the front across northern and northeast Wyoming into
western South Dakota. Temperatures ahead of the front were in the
mid 30s to low 40s, with 20s to low 30s behind the front. It was
breezy west of the Laramie Range with west winds gusting 35 to 45
mph.
Forecast concerns the next 24 hours will focus on precipitation,
QPF/snowfall accumulations and temperatures.
Latest short term model/ensemble guidance has been consistent with
the southeastward track of the shortwave across southeast Wyoming
and western Nebraska later today and tonight. Adequate moisture
and isentropic upglide/QG ascent above the stalled surface boundary
near the Laramie Range will produce widespread snow between 4500
and 8500 feet along and east of the Laramie Range and over the
Snowy Range today, with rain and snow west of the Laramie Range
where daytime temperatures will be in the 30s and 40s. Snow is
expected tonight, continuing into Sunday morning before ending.
Looking at advisory snowfall accumulations (3 to 8 inches) along
and east of the Laramie Range, with locally heavy snow for the
Snowy Range where 6 to 12 inches is expected. Blowing snow will
not be an issue with lighter winds, however travel will be
hazardous due to low visibilities and slick/snow covered roadways.
The stalled front near the Laramie Range will retreat east
Sunday, with slightly milder temperatures. It will be breezy to
windy Sunday afternoon and night as the 700mb gradient flow
increases to 45 to 55m with tight east to west surface pressure
gradient.
.LONG TERM...(Monday through Friday)
Issued at 310 AM MDT Sat Mar 31 2018
Models showing a little better run to run consistency this morning
depicting a cold front moving through late Monday into Tuesday as
a shortwave passes across the central Rockies, bringing a brief
period of rain and snow (accumulations do not appear overly
significant). We still expect to see a drier and warmer period
Wednesday into Thursday with shortwave ridging across the area,
then as a stronger closed low system moves southeastward across
the northern Plains, we will see another cold front move down the
east side of the Rockies bringing another shot at precipitation
for late week into the weekend.
&&
.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 532 AM MDT Sat Mar 31 2018
Models continue to trend downward on ceilings and visibilities for
most locations this afternoon into the evening, particularly for
the Cheyenne area and for points to the east and northeast. Kept
this trend going in the early morning aviation package in the area
that the HRRR is setting up a wide band of snowfall from
southeastern Wyoming into the central Nebraska Panhandle. Lowest
visibilities will most likely occur 00z-06z from Scottsbluff to
Alliance.
&&
.FIRE WEATHER...
Issued at 230 AM MDT Sat Mar 31 2018
An arctic cold front will stall near the Laramie Range today and
tonight. A potent upper level weather disturbance will track southeast
along this boundary and produce widespread light to moderate snowfall
this afternoon through early Sunday morning for much of southeast
Wyoming into western Nebraska. The snow may be heavy at times over
the Snowy and northern Laramie Ranges, as well as central portions
of the Nebraska Panhandle. The snow will taper off Sunday morning
as the front and disturbance move to the east. Dry and warmer weather
will return Sunday and Monday, along with breezy to windy conditions.
Another cold front will bring rain and snow showers and much cooler
temperatures late Monday into Tuesday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from noon today to noon MDT Sunday for
WYZ101>103-106>108-116>119.
Winter Storm Warning until noon MDT Sunday for WYZ114.
NE...Winter Weather Advisory from noon today to noon MDT Sunday for
NEZ002-003-019>021-054-055-095-096.
&&
SHORT TERM...MAJ
LONG TERM...JG
AVIATION...JG
FIRE WEATHER...MAJHazardous Weather Outlook...CORRECTED National Weather Service Cheyenne WY 441 AM MDT Sat Mar 31 2018 NEZ002-003-019>021-054-055-095-096-WYZ101>103-106>108-116>119- 011045- Dawes-Box Butte-Scotts Bluff-Banner-Morrill-Kimball-Cheyenne- North Sioux-South Sioux-Converse County Lower Elevations- Niobrara County-North Laramie Range- Central Laramie Range and Southwest Platte County- East Platte County-Goshen County-South Laramie Range- South Laramie Range Foothills-Central Laramie County- East Laramie County- 441 AM MDT Sat Mar 31 2018 This hazardous weather outlook is for portions of western Nebraska...east central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT A potent upper level weather disturbance will track southeast across the area today and tonight. Widespread accumulating snow is forecast, with 3 to 6 inches east of the Laramie Range into western Nebraska, and 6 to 8 inches for the northern Laramie Range. Winter Weather Advisories are in effect this afternoon and tonight. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY The snow will end Sunday afternoon. Strong and gusty winds wil develop Sunday afternoon and night for the central and southern Laramie Range and adjacent foothills. Gusts of 40 to 50 mph are expected. More rain and snow is forecast Monday and Monday night, and later in the week. .Spotter information statement... Spotter activation will not be required. Spotters are encouraged to report snowfall amounts. WYZ114-011045- Snowy Range- 441 AM MDT Sat Mar 31 2018 This hazardous weather outlook is for portions of south central Wyoming. .DAY ONE...TODAY AND TONIGHT Periods of moderate to heavy snow will fall over the Snowy Range today and tonight. Accumulations of 6 to 12 inches, locally higher above 10000 feet, are expected. Outdoor recreationists should be prepared for low visibility and difficult travel. A Winter Storm Warning is in effect from 6 AM this morning through Noon Sunday. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY The snow will end Sunday afternoon. More snow is forecast Monday and Monday night, and later in the week. .Spotter information statement... Spotter activation will not be required. Spotters are encouraged to report snowfall amounts. WYZ104-105-109>113-115-011045- Ferris/Seminoe/Shirley Mountains-Shirley Basin- Central Carbon County-North Snowy Range Foothills- Southwest Carbon County-Sierra Madre Range- Upper North Platte River Basin-Laramie Valley- 441 AM MDT Sat Mar 31 2018 This hazardous weather outlook is for portions of south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Periods of rain and snow are expected today and tonight. Snow accumulations of 2 to 4 inches are forecast for the Sierra Madre Range and northern Carbon County, with 1 to 2 inches for the foothills and higher valleys. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY The snow will end Sunday afternoon. Strong and gusty winds will develop Sunday afternoon and night. Gusts of 40 to 50 mph are expected. More rain and snow is forecast Monday and Monday night, and later in the week. .Spotter information statement... Spotter activation will not be required. Spotters are encouraged to report snowfall amounts.
The national radar mosaic for the moment the first event began.
3 winter storm. Local standard time, as filed.
The Sand Lake SNOTEL site (elevation 10050 ft) estimated 12 inches of snow.
The Brooklyn Lake SNOTEL site (elevation 10240 ft) estimated 14 inches of snow.
The Medicine Bow SNOTEL site (elevation 10500 ft) estimated 14 inches of snow.
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, March 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: 761060, 761062, 761064.