An unstable northwest flow aloft resulted in some heavy snow for the Northeast Bighorn Mountains and Sheridan Foothills.
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The episode as NWS BYZ wrote it up.
An unstable northwest flow aloft resulted in some heavy snow for the Northeast Bighorn Mountains and Sheridan Foothills.
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 6, 2:53 AM MST, 1 hour 37 minutes earlier.
Area Forecast Discussion
National Weather Service Billings MT
353 AM MDT Sat Apr 6 2024
.DISCUSSION...
Through Sunday night...
Highlite changes...Added Judith Gap and more central zones to the
going Winter Weather Advisory. More snow accumulation expected in
the foothills around Judith Gap today into tonight, and northerly
winds funneling through that area will bring the threat of poor
visibility in blowing snow. Added more central zones for the heavy
wet snow in the higher hilltop locations within this area
including the Hysham Hills and Bull Mountains. This heavy snow is
not expected to impact the population centers or travel for most
of these zones as they are at an elevation low enough that a lot
of snow will melt, and roads are expected to stay wet to slushy
for the most part. A threat that is increasing is power outages as
wind gusts over 40 mph will be widespread along with the heavy wet
snowfall sticking to trees and power lines.
Synoptic Discussion...500mb low consolidates energy this morning
over southern Idaho and then tracks east/southeast across Wyoming
and moves into the Nebraska panhandle by early evening. From
tonight through early Tuesday the upper low slows down and pivots
north to northwest into the eastern Dakotas, linger energy and
advecting moisture from the plains into the forecast area. Strong
jet level divergence aloft combines with strong low level
convergence, QG forcing aloft, a strong 700mb frontogenesis band
over the region, and strong plains moisture advection to bring
periods precipitation (moderate to heavy at times) to the area
from this morning into Monday. This synoptic pattern is one of the
northern Rockies best precipitation producing patterns, and this
is reflected in the current forecast. The one area that doesn't
quite get in on the heavier precipitation are areas to the west of
Billings. This is due to the system tracking a bit fast and
further south than optimal today. This system is not pulling in
really cold air and will be relying on dynamic cooling and cold
temperatures aloft for much of its snow production. This can be
tricky to forecast as the dynamics responsible for the cooling can
be in slightly different places/different strengths in the models.
This is resulting in very heavy snow accumulations for the
Bighorn/Crazy mountains as well as the higher hills to the east
of Billings and down into Powder River county, while the lower
elevations/river valleys are not looking at significantly
impactful snow but significant precipitation.
Precipitation should blossom over the central and western forecast
area around sunrise as a strong divergent pattern develops aloft
with a jet streak bailing out to the northwest of the area. A
second jet streak pushes in from the southeast moving northwest
tonight. This will pull precipitation potential eastward for the
eastern half of the area getting into the precipitation after a
mainly dry Saturday. More energy wraps northwest of the upper low
Sunday into Monday. This energy is less vigorous than what arrives
today/tonight, so precipitation rates will drop a bit, but still
expect good widespread precipitation into Monday.
72 hour rainfall amounts through Monday are looking like a
quarter of an inch for the western foothills, up to 2 inches in
the central zones between Billings and Hardin, and around half an
inch east to Baker. There is a sharp divide along a Ryegate to
Billings line between lower precipitation amounts around half an
inch and 1.5+ inches. For Billings this puts the reasonable range
of precipitation from 0.5in (75%) to 1.5in (40%). The latest GFS
ensembles came in a bit higher with the latest run pushing our NBM
deterministic forecast toward the higher end at 1.4 inches in
Billings, but this could easily change with just a slight jog to
the east with the best dynamics.
Here are precipitation probabilities for over an inch:
Livingston 10%
Billings 60%
Sheridan 75%
Hardin 75%
Ashland 80%
Miles City 60%
Baker 30%
Broadus 70%
As mentioned above snowfall with this system will be mainly
confined to the mountains, higher foothills, and highest hills
across the plains. But where it falls it looks very heavy, with
the Bighorn/Crazy mountains looking at up to 3 feet of snowfall
from this storm, and the higher hills (Bull and Wolf Mountains,
Lame Deer Divide, Hysham Hills etc) seeing 8 to 18 inches of snow.
Combine the snow with the strong northwest winds gusts associated
with this system and blowing/drifting snow and power outages
become a significant threat for rural locations.
We are going to watch the southern Bighorn/Sheridan foothills
zones for a possible upgrade to a Winter Storm Warning, or
possibly a Blizzard warning tonight. Wind gusts have increased in
the models to around 60 mph if not a bit stronger and snow rates
in the higher terrain look heavy. Metro model is keeping road
temperatures just above freezing all night at 35 degrees which
would limit the icy road concerns, but the combination of wind,
visibility and snow rates may be enough to warrant the upgrade,
along with power outage potential.
Snowfall probabilities for over 3 inches of snow:
Livingston 10%
Sheridan 30%
Lame Deer 45%
Colstrip 15%
Broadus 25%
Billings, Hardin, Baker, Miles City, Roundup 0%
Still time for this system to shift a bit, and small shifts with
a system as dynamic as this one can produce big sensible weather
differences. So stay tuned to the forecast for the latest
information through the weekend. Chambers
Monday through Friday...
Rain and snow associated with the low will dissipate and move east
through the day. The Bighorns and Pryors have about a 40-60%
chance of getting an additional 2 inches of snow with the
Beartooth/Absarokas at a 15-25% chance. Any additional rainfall
accumulations Monday will likely be less than a quarter inch.
Ensembles have ridging attempting to build back in late Monday,
with additional disturbances Monday evening and Tuesday afternoon
into Wednesday. PoPs will be highest for those along the mountains
and foothills (30-50%) Tuesday night into Wednesday afternoon
with lower elevations at 15-25%. More pronounced ridging will
build in for Thursday and Friday, allowing for warm and dry
conditions. Friday into Saturday, ensembles are hinting at a
possible shortwave trough that could bring unsettled weather for
the weekend.
High temperatures will be in the 40s/50s Monday, 50s/60s Tuesday
through Thursday and 60s/70s Friday. TS
&&
.AVIATION...
Scattered showers will continue overnight as a more prominent band
of showers develops from KBIL down to KSHR. KLVM and KMLS will see
showers later in the afternoon. NW Wind gusts will generally
increase throughout the day being most prominent at KBIL (25-30
kts) and KSHR (30-35 kts). These factors will likely create
MVFR/IFR conditions for most of the period. Mountain obscurations
are also likely, especially over the Bighorns where heavy snow and
gusty winds are expected. TS
&&
.PRELIMINARY POINT TEMP/POPS...
Tdy Sun Mon Tue Wed Thu Fri
-------------------------------------------------------
BIL 043 034/042 035/052 032/060 038/060 036/065 042/072
+/T 89/O 96/O 00/B 12/R 01/B 13/R
LVM 041 030/040 031/049 031/055 033/058 035/062 040/067
6/O 56/O 62/S 01/B 11/B 01/B 13/R
HDN 044 032/039 032/049 029/060 035/059 034/063 037/072
9/T ++/O +8/R 00/B 12/R 10/U 12/R
MLS 056 035/041 034/048 032/057 038/058 035/060 038/070
5/R 99/R 88/R 10/B 11/U 00/U 11/B
4BQ 053 031/036 031/042 031/054 036/055 034/060 037/071
8/R ++/O 98/O 10/U 11/U 00/U 01/B
BHK 057 034/041 030/047 032/055 035/056 031/057 034/066
4/R 78/O 77/O 10/B 02/R 00/U 01/B
SHR 042 030/037 030/045 027/055 032/054 031/060 035/069
9/T 99/O 98/O 00/B 22/R 11/U 02/R
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory in effect from 6 PM this evening to 6
PM MDT Sunday FOR ZONES 29>31-57-173.
Winter Weather Advisory remains in effect from 6 PM this
evening to noon MDT Monday FOR ZONES 36-58-138.
Winter Weather Advisory in effect until 10 AM MDT Sunday FOR
ZONE 63.
Winter Storm Warning remains in effect until 6 PM MDT Monday
FOR ZONE 171.
WY...Winter Weather Advisory remains in effect from 6 PM this
evening to noon MDT Monday FOR ZONE 199.
Winter Storm Warning remains in effect until 6 PM MDT Monday
FOR ZONE 198.
&&
weather.gov/billingsPreliminary Local Storm Report
National Weather Service Billings, MT
1201 AM MDT Sat Apr 06 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1030 PM Non-Tstm Wnd Gst 5 ENE Plevna 46.44N 104.43W
04/05/2024 M52.00 MPH Fallon MT Mesonet
&&
TSThe national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
Area Snotels received 13 to 30 inches of snow.
The Leiter area received 7 inches of snow. In addition, blizzard conditions were reported across the area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2024Every state in 2024This day in weather historyWarnings in Wyoming, April 2024
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: 1168827, 1168828.