The seasons first winter storm impacted the Crazy and Absaroka/Beartooth Mountains. Snowfall amounts were around 10 inches.
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.
The seasons first winter storm impacted the Crazy and Absaroka/Beartooth Mountains. Snowfall amounts were around 10 inches. This was more of an impact given the Beartooth Highway was still open for the season and it was the seasons first snowfall.
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 Sep 14, 8:13 PM MST, 47 minutes earlier.
Area Forecast Discussion...Updated
National Weather Service Billings MT
913 PM MDT Thu Sep 14 2017
.UPDATE...
Very minor tweaks to precipitation timing and low temperatures
tonight. Low temperatures seem a bit aggressive in the models
across western foothills and valleys given consistent
precipitation, upslope winds and near saturated lower third of the
atmosphere. Struggling to see temperatures in the 30s in these
areas without some dry air intruding in from somewhere, and not
seeing much of that upstream until you get to Canada, or dynamic
cooling increasing more than is forecast. Best QG forcing arrives
after sunrise. So, bumped temperatures up a few degrees over
western zones to around 40 degrees for lows. Also looking a bit
warmer than anticipated in the Bighorn mountains so adjusted
precipitation type to more rain/snow mix overnight until that
enhanced QG forcing arrives tomorrow morning which should snap
precipitation over to all snow above 7000 feet. Wind chills will
be running in the 30s overnight through tomorrow morning. Cold
and wet for Friday. No changes to overall Snow/QPF or Winter Storm
Warnings. Chambers
&&
.SHORT TERM...valid for Fri and Sat...
The advertised wet and cool pattern is moving in as a deep upper
trough over southern British Columbia slides into the northern
Rockies. Strong ascent and deep upslope flow will allow for a
prolonged period of rainfall. Showers will develop over western
and northern locations today and become more widespread tonight as
they slide east. Un upper low spinning over southern Nevada, will
get pulled in tonight and bring some deeper moisture with it. The
period of heaviest precipitation looks to be tonight and Friday
as the BC trough and the Nevada upper low combine and shift across
the forecast area. High PoPs look on track, as does existing QPF
amounts. The shift of the heavier precipitation into the southeast
looks consistent on all models as well. All in all, the entire
area will get a good shot of precipitation with most areas seeing
at least an inch to an inch and a half of QPF, with some spots
picking up 2 inches through Saturday.
Snow levels will drop tonight into Friday as temperatures cool
aloft. Accumulating snowfall is expected above 7,000 feet through
Friday, and as 850mb temperatures drop to around 2c Friday night,
some of the higher hills could get a light accumulation of wet
snow too. Red Lodge could pick up a rain and snow mixture through
the day Friday and this could accumulate to a couple inches of
snow by Saturday morning. Confidence on foothills snow not as high
given warm ground, high sun angle during the day, and 850mb
temperatures staying above zero, so will not issue a highlight at
this time for these locations. Will need to be watched however.
Confidence is high on snow amounts for the mountains. Warm ground
and wet snow will tend to limit snow amounts, but a long duration
event producing upwards of a foot of snow is expected in the
Beartooth and Absaroka mountains. The Bighorns will also see heavy
snow with totals approaching a foot. Given that this is a big,
early season event, with heavy wet snow, will upgrade the watches
to warnings and continue to heighten the awareness on the
potential dangers this storm could bring for those unprepared.
High temperatures will be dramatically colder by Friday with many
locations not getting out of the 40s, with overnight lows falling
into the 30s (which is around 30 degrees below climatology)!
Quite the change! TWH
.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...
Another system is in the offing for late in the extended period
after the Saturday system exits the area. While both the GFS and
ECMWF showed a late period system, model agreement on the
evolution of the system was quite poor, probably at least in part
due to tropical systems affecting the model solutions.
Jet divergence will be moving out of the east on Sat. as an upper
trough shifts E through the area. Strong q-vector convergence will
accompany this system as well as ample moisture and upslope flow.
Thus have raised PoPs across the area into the likely and categorical
range in the morning and had a high chance in the afternoon. Went
a bit lower with high temperatures than blended guidance given the
cold airmass, clouds and precipitation. Mountain snow amounts
still looked like they would be around an inch and nearby
foothills could see less than half an inch of snowfall.
Precipitation will taper off Sat. evening as the trough shifts E.
Zonal flow will lead to a dry day on Sunday. A weak wave may
produce a few showers over the E in the evening. Brief upper
ridging on Monday will give way to SW flow ahead of the next upper
low. Went with chance PoPs over the W Mon. night with possible
thunder in the evening based on low LI's. Temperatures will reach
the 70s on Monday. By Tuesday, models were in poor agreement with
the GFS bringing the upper low along the MT/Canadian border and
the ECMWF keeping SW flow over the area. Blended guidance gave
isolated to scattered PoPs central and E with temperatures mainly
in the 60s. The model disagreement continued through Thursday, but
despite this, expect a chance of precipitation each period. Arthur
&&
.AVIATION...
Light to moderate rain is overspreading much of the region, and
will continue throughout the TAF period. CIGS range from IFR/LIFR
from KBIL west to MVFR east and should settle toward IFR/LIFR
across the region overnight. VIS is generally IFR in areas
receiving rain, and VFR/MVFR elsewhere. VIS should trend toward
IFR in most location overnight, but may fall into LIFR range with
locally heavier rain. The mountains will be obscured through
tonight. AAG
&&
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
-----------------------------------------------------------
BIL 043/048 038/054 038/069 045/076 046/064 044/067 043/067
++/R 87/R 20/B 01/B 35/T 23/W 34/W
LVM 040/046 030/051 028/065 037/071 038/060 035/064 034/065
++/R 87/O 10/B 01/N 55/T 33/W 45/W
HDN 045/053 037/059 034/072 040/080 042/067 040/069 039/070
++/R 87/R 20/B 01/B 24/T 23/W 34/W
MLS 045/052 038/055 034/069 042/079 047/070 042/070 042/072
++/R 77/R 20/U 10/U 23/T 22/W 44/W
4BQ 046/052 036/054 032/069 041/079 048/071 041/070 041/073
++/R 75/R 20/U 00/U 02/T 34/W 44/W
BHK 045/050 037/051 034/066 041/078 048/071 042/070 042/070
++/R 76/R 30/B 10/U 12/T 22/W 44/W
SHR 044/047 033/053 029/068 037/078 042/067 037/066 035/068
++/R 86/R 20/B 00/U 23/T 34/W 44/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until 6 PM MDT Saturday FOR
ZONES 67-68.
WY...Winter Storm Warning in effect until 6 PM MDT Saturday FOR
ZONE 98.
&&
weather.gov/billingsThe national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
The Beartooth Pass was closed at Vista Point. This was the first snow of the season and a quick pattern change.
Around 9 inches of snow fell across the southeast foothills. This was the first snow of the season and a quick pattern change.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2017Every state in 2017This day in weather historyWarnings in Montana, September 2017
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: 718807, 718804.