Winter Storm in Wyoming, December 29 to 30, 2017

Name: Winter Storm in Wyoming, December 29 to 30, 2017
Start: 2017-12-29T00:00
End: 2017-12-30T14:00
Location: Wyoming

December 29 to 30, 2017 · NWS BYZ · 1 event in 1 county or zone

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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.

What happened

The episode as NWS BYZ wrote it up.

A very strong arctic front moved across the Billings Forecast area during the early morning hours of the 28th. At the same time, a fetch of deep Pacific moisture moved off the Pacific and across the northern Rockies. This pattern persisted for about 48 hours. Temperatures were mainly in the single digits above and below zero through the period. This resulted in very high snow ratios which equated to high snow total amounts. In addition, gusty north to northeast winds resulted in widespread blowing and drifting snow. The main impact from this winter storm was difficult to impossible traveling conditions.

What forecasters said that day

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 Dec 28, 9:32 PM MST, 2 hours 28 minutes earlier.

Area forecast discussion, Dec 28, 9:32 PM MST, 2 hours 28 minutes before

Area Forecast Discussion...Updated
National Weather Service Billings MT
932 PM MST Thu Dec 28 2017

.UPDATE...
Not much snow has occurred this evening over the area as forcing
mechanisms have been weak. A fairly persistent band over Rosebud,
Treasure and N. Big Horn County was due to 700 mb warm advection
and frontogenesis as well as a weak shortwave. Other weak
frontogenesis was combining with isentropic lift to bring periods
of very light snow to various parts of the area. Satellite showed
the strong Pacific moisture fetch streaming into the region. At
the surface, the arctic front was anchored between KLVM and Big
Timber for much of the evening with SW winds gusting to around 50
mph at KLVM and temperatures approaching 40 degrees, while Big
Timber was close to 10 degrees with a light E wind. Models showed
NE upslope flow increasing overnight as lift aloft increases due
to shortwaves moving through the NW flow. The lift will combine
with the moisture to produce increasing chances of snow overnight
into the Friday morning commute. Adjusted PoPs to reflect the
trends for the night. Also adjusted hourly grids and Min temps to
reflect the frontal position E of KLVM. Some rain will likely mix
with the snow at KLVM for a brief time. This could add ice to
roads that will become snow-covered. Will issue a wind graphic for
KLVM to show chances of 50 mph winds.

Pressure rises will move over the area Fri. morning as a
shortwave, seen moving through S BC this evening on water vapor,
passes through NE MT. These rises will push the front back through
KLVM. Moderate to heavy snow will occur on Friday into Fri. night
over the central and western portions of the area. No changes
needed to winter highlights. Arthur

&&

.SHORT TERM...valid for Fri and Sat...

Most important message...snow is expected to increase overnight
and especially Friday during the day. Friday night looks to see
the heaviest snowfall with a variety of weather conditions
expected on Saturday as the coldest air begins to shift around.
There already is 4 to 8 inches of snow on the ground across the
region at a minimum a new snowfall is expected to be close to a
foot for many areas. Travel is going to be challenging...and
getting stuck on a rural road could be dangerous.

Water vapor imagery shows moisture deepening over the area with a
shortwave moving into central BC flattening a weak ridge along the
west coast a bit. This temporarily pushed the core of the surface high
pressure eastward a bit and best slope along the arctic is
currently oriented a Cut Bank to Broadus line with less
precipitation currently occurring west of this band.
The approach of the wave overnight brings lift to the area and
with the deeper moisture increases snowfall across south central
Montana though a few locations along the foothills may see
downslope for a portion of the night. The passage of the wave late
tonight allows the arctic to deepen with increasing northeasterly
winds increasing upslope tonight though a brief period of
subsidence aloft may hold up the increase in snowfall rates a few
hours tomorrow morning.

Deeper moisture with increasing upslope and isentropic lift
combine to accelerate snowfall tomorrow with bufr soundings
showing a seeder feeder pattern which will help dendrite size
despite bitter low level cold temperatures. This band of snowfall
persists through the day and increases Friday night as a wave
moving into the Pacific Northwest increases warm air advection in
the mid levels but pressure falls west of the divide pull the
arctic east of the divide in further. This brings the heaviest
period of snowfall for Billings and areas west of Billings.

By later Saturday morning the BC wave is shifting east of the area
which pulls the arctic east and brings a complex weather picture
over the western zones where westerly winds may bring mixing to
areas like Livingston...Big Timber and Harlowton. NAM even pulls
the coldest air east of Billings briefly before the arctic surges
back westward in the evening. Either way this begins to slow down
snowfall on Saturday and begins to introduce a blowing snow
threat...just the areal coverage across the western zones is
unclear.

Saturday night will be bitter cold with northeasterly winds around
10 mph producing wind chills of 20 to 30 below zero. Still appears
to be a fair amount of moisture around initially so how far
temperatures actually fall will be dependent on cloud cover.
borsum

.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...

After snow event, we transition to a drier period for this
extended with concerns shifting to any potential blowing snow
behind this system early next week. Overall upper level northwest
flow will dominate. Surface lee side troughing will begin to
develop on Monday to kick off some initial southwesterly drainage
winds, but highest winds should develop late Monday night into
Tuesday as a fast moving clipper dives south out of Canada to our
northeast. The subsequent increased pressure gradient as the
arctic air tries to retreat should bring in more gusty winds. This
wind event looks to be short lived and gradient relaxes quickly
late in the day on Tuesday. Local gusts to 40 mph, especially for
areas from Billings westward, will increase blowing snow potential
with the focus for this late Monday night into Tuesday.
Otherwise, temperatures will be moderating. 2017 will end on a
cold note with below zero high temperatures, but rebounding
temperatures close to the freezing mark by Wed/Thurs. Frieders

&&

.AVIATION...

Snow will be on the increase this evening across the region as
impacts begin developing with major winter storm. IFR and LIFR
conditions and mountain obscurations will continue into Saturday
with low ceilings and visibilities. Frieders

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 001/002 910/000 916/902 914/014 009/028 009/025 011/033
    ++/S    +8/S    62/S    10/U    00/Q    00/B    00/B
LVM 022/023 004/023 003/016 003/023 014/031 020/033 016/037
    9+/S    +8/S    62/S    01/U    00/Q    00/N    10/N
HDN 000/003 910/001 918/902 918/009 004/026 009/024 008/031
    ++/S    +8/S    62/S    10/U    01/B    00/B    00/B
MLS 906/902 915/905 925/906 923/005 001/020 003/020 005/027
    9+/S    99/S    62/S    10/U    00/B    10/B    00/B
4BQ 901/003 914/902 921/905 918/008 002/023 006/021 009/030
    9+/S    +8/S    51/I    00/U    01/B    10/B    00/B
BHK 906/904 918/908 927/908 926/004 001/016 903/014 005/024
    89/S    78/S    62/S    00/U    00/B    00/B    00/B
SHR 007/009 905/010 909/005 909/014 005/028 011/027 011/035
    47/S    97/S    62/S    00/U    00/B    00/B    00/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until midnight MST Saturday
      night FOR ZONES 28>32-34>36-38>42-56>58-63>68.
     Winter Weather Advisory in effect until midnight MST Saturday
      night FOR ZONES 33-37.
WY...Winter Storm Warning in effect until midnight MST Saturday
      night FOR ZONE 98.
     Winter Weather Advisory in effect until midnight MST Saturday
      night FOR ZONE 99.

&&

weather.gov/billings

In the hours before

Local storm report, Dec 28, 11:27 PM MST, 33 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BILLINGS MT
1127 PM MST THU DEC 28 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     SNOW             1 NW COLUMBUS           45.64N 109.27W
12/28/2017  M5.4  INCH       STILLWATER         MT   CO-OP OBSERVER

0400 PM     SNOW             18 SW FISHTAIL          45.24N 109.73W
12/28/2017  M4.0  INCH       STILLWATER         MT   CO-OP OBSERVER

0500 PM     SNOW             1 S RED LODGE           45.18N 109.26W
12/28/2017  M2.5  INCH       CARBON             MT   CO-OP OBSERVER

0500 PM     SNOW             HYSHAM                  46.29N 107.23W
12/28/2017  M2.0  INCH       TREASURE           MT   CO-OP OBSERVER

0545 PM     SNOW             5 NW FORSYTH            46.34N 106.70W
12/28/2017  M3.0  INCH       ROSEBUD            MT   TRAINED SPOTTER

0600 PM     SNOW             BUSBY                   45.54N 106.96W
12/28/2017  M1.5  INCH       BIG HORN           MT   CO-OP OBSERVER

0600 PM     SNOW             3 ENE RIDGEWAY          45.50N 104.45W
12/28/2017  M2.0  INCH       CARTER             MT   CO-OP OBSERVER

0600 PM     SNOW             8 WSW BIDDLE            45.04N 105.49W
12/28/2017  M1.2  INCH       POWDER RIVER       MT   CO-OP OBSERVER

0600 PM     SNOW             20 ESE COLSTRIP         45.82N 106.23W
12/28/2017  M1.4  INCH       ROSEBUD            MT   CO-OP OBSERVER

0600 PM     SNOW             8 NNE POWDERVILLE       45.85N 105.04W
12/28/2017  M1.5  INCH       CUSTER             MT   CO-OP OBSERVER

1018 PM     NON-TSTM WND GST 6 ENE LIVINGSTON        45.70N 110.45W
12/28/2017  M58.00  MPH      PARK               MT   ASOS

&&

WD

Event by event

1 winter storm. Local standard time, as filed.

Winter Storm, Sheridan Foothills

When: December 29, 12:00 AM MST to December 30, 2:00 PM MST
Where: Sheridan Foothills forecast zone
Reported by: Trained Spotter

There were several 8+ inch snowfall reports east of Interstate 90.

What these are

Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Wyoming in 2017 Every state in 2017 This day in weather history Warnings in Wyoming, December 2017

Sources

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: 727476.