High Wind in Montana, December 12, 2018

Name: High Wind in Montana, December 12, 2018
Start: 2018-12-12T01:20
End: 2018-12-12T01:52
Location: Montana

December 12, 2018 · NWS TFX · 2 events in 2 counties and zones

Potent open wave bringing strong winds to the area. Models back off on the H700 flow over the entire region overnight, as well as pushing the strongest winds a bit further south over Central Montana.

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 2

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 TFX wrote it up.

Potent open wave bringing strong winds to the area. Models back off on the H700 flow over the entire region overnight, as well as pushing the strongest winds a bit further south over Central Montana. Increasing H700 cross barrier flow and strengthening pressure gradient during the evening hours allow winds to increase again.

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 Great Falls, MT wrote its last area forecast discussion before the first event at Dec 11, 10:30 PM MST, 2 hours 50 minutes earlier.

Area forecast discussion, Dec 11, 10:30 PM MST, 2 hours 50 minutes before

Area Forecast Discussion
National Weather Service Great Falls MT
1030 PM MST Tue Dec 11 2018

...Aviation Section Updated...

.SYNOPSIS...
Strong winds are expected over the next 36 to 48 hours across
much of Southwest and North Central Montana, especially along the
Rocky Mountain Front and plains west of the Interstate 15
corridor. Snow develops along the Continental Divide and over the
mountains and passes of Southwest Montana. Travel could be very
difficult to near impossible over Western Glacier County into
Wednesday, as strong winds and falling snow lead to blizzard
conditions.

&&

.UPDATE...
Did make some changes to temps and winds in the near-term. Temps
were bumped up some to reflect how the strong downsloping winds
have kept temps up above the initial forecast. CONSMOS (and the BC
version) seemed to have a better handle on the temps, so these
were blended in with the previous forecast. As for winds, some
northern sites (especially Great Falls and Cut Bank) were stronger
than forecast, so winds were boosted some through 09z. After
dropping around 00z, Cut Bank has been flirting with sustained
winds near high wind warning criteria, and GTF also recently
briefly gusted near the 50kt criteria. Winds will likely continue
to surge some off and on through the night, so TAFs may require
some amendments through the night.

&&

.AVIATION...
Updated 0530Z.

MVFR/IFR conditions are expected to return to the KEKS and KBZN
terminals between 09-12z Wednesday as ceilings lower and snow
develops ahead of the next upper level disturbance. In addition,
MVFR conditions are also expected to develop between 15-18z
Wednesday at the KHVR and KLWT terminals also because of developing
snow and lowering ceilings. Otherwise, VFR conditions are expected
for the KHLN, KGTF, and KLWT terminals throughout the duration of
the 1206/1306 TAF period, however, increasing mid-level cloudiness
will bring lowering ceilings. Mountain obscuration is likely across
Southwest Montana and along the Continental Divide for much of the
TAF period. Winds will also remain strong and gusty at most
terminals, especially at the KCTB, KHVR, KGTF, KLWT, KHLN, and KEKs.
Mountain wave turbulence and low level wind shear will be a concern
for much of the TAF period. - Moldan

&&

.PREV DISCUSSION...
/ISSUED 226 PM MST Tue Dec 11 2018/
Today through Wednesday night...Trough crossing the area from the
west into Wednesday means primary forecast concerns remain
accumulating mountain/pass snow and high winds. Strong winds
continue through Wednesday afternoon, especially along the Rocky
Mountain Front and over the plains of North Central Montana.
Temperatures will remain slightly above seasonal norms.

Lee-side surface trough was strengthening along the Rocky
Mountain Front, which was leading to a strong pressure gradient
over the area. The strengthening pressure gradient along the
Rocky Mountain Front has already led to wind gusts of 60 to 75
mph in some locations, which has only helped to build confidence
in the current High Wind Warning that is in place through
Wednesday. As the pressure gradient strengthens further and
cross barrier flow reaches 50 to 70 knots, high winds with gusts
to 80 mph along the immediate Rocky Mountain Front and 65 mph over
the plains, are expected by late this afternoon/early this
evening. A stable layer at/near ridgetops will aide further in
momentum transfer to the surface from mountain wave activity. A
High Wind Watch has been upgraded to a High Wind Warning for the
plains of North Central Montana from Wednesday morning through
Wednesday evening. Daytime mixing and the passage of the trough
axis on Wednesday will aide in the potential for 60 mph wind gust
over the plains of North Central Montana.

Orographic lift and increasing ascent from the next fast moving
open wave will lead to precipitation development, in the form of
snow, along the Continental Divide and over the mountains of
Southwest Montana from this afternoon and through most of the day
on Wednesday (precipitation has already developed in some areas
along the Continental Divide this morning). Snowfall
accumulation at Marias Pass of 8-12" and 1-4" at East Glacier are
expected. The combination of falling snow and strong winds
mentioned previously will lead to Blizzard condtions from this
evening into the day Wednesday. Travel could be very difficult to
near impossible for those traveling on United States Highway 2
from East Glacier to Marias Pass and United States Highway 89 from
Kiowa to Saint Mary. Snowfall accumulations of to 3-6 inches at
Big Hole Pass and 6-9 inches at Chief Joseph Pass means a
continuation of the Winter Weather Advisory for Beaverhead
County. Snowfall accumulations of 4-8" are expected above 6000
feet in Madison and Gallatin Counties, which will lead to
difficult travel conditions, especially in areas of blowing snow.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  32  40  26  42 /  10  10   0   0
CTB  28  38  24  41 /  30  30   0   0
HLN  26  37  19  38 /  40  20   0   0
BZN  23  35  12  32 /  60  40   0   0
WEY  15  25  -1  21 /  90  90  10  20
DLN  19  33   7  29 /  80  60   0   0
HVR  29  40  22  42 /  20  40   0   0
LWT  29  38  21  41 /  10  40  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 6 AM to 5 PM MST Wednesday Blaine...
Cascade...Chouteau...Eastern Pondera...Eastern Teton...Fergus...
Hill...Judith Basin...Liberty...Toole.

Winter Weather Advisory until 5 PM MST Wednesday Beaverhead.

Winter Weather Advisory until 5 PM MST Wednesday Gallatin...
Madison.

Blizzard Warning until 11 AM MST Wednesday Northern Rocky
Mountain Front.

High Wind Warning until 11 AM MST Wednesday Eastern Glacier...
Northern Rocky Mountain Front...Southern Rocky Mountain Front.

&&

http://www.weather.gov/greatfalls

In the hours before

Local storm report, Dec 11, 11:14 PM MST, 2 hours 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1114 PM MST TUE DEC 11 2018

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

1029 PM     NON-TSTM WND GST 2 SW CAMERON            45.19N 111.70W
12/11/2018  M57 MPH          MADISON            MT   MESONET

&&

JF

Local storm report, Dec 11, 11:17 PM MST, 2 hours 3 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1117 PM MST TUE DEC 11 2018

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

1044 PM     NON-TSTM WND GST 2 SW CAMERON            45.19N 111.70W
12/11/2018  E61 MPH          MADISON            MT   MESONET

&&

JF

Local storm report, Dec 11, 11:38 PM MST, 1 hour 42 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1138 PM MST TUE DEC 11 2018

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

1029 PM     NON-TSTM WND GST 2 SE BROWNING           48.54N 112.98W
12/11/2018  M74 MPH          GLACIER            MT   MESONET

&&

MOLDAN

Local storm report, Dec 11, 11:56 PM MST, 1 hour 24 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1156 PM MST TUE DEC 11 2018

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

1130 PM     NON-TSTM WND GST 14 W BYNUM              47.98N 112.61W
12/11/2018  M69 MPH          TETON              MT   MESONET

&&

MOLDAN

Local storm report, Dec 12, 1:05 AM MST, 15 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
105 AM MST WED DEC 12 2018

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

1152 PM     NON-TSTM WND GST 7 ESE HILGER            47.22N 109.22W
12/11/2018  M58 MPH          FERGUS             MT   MESONET

&&

MOLDAN

Local storm report, Dec 12, 1:07 AM MST, 13 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
107 AM MST WED DEC 12 2018

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

1058 PM     NON-TSTM WND GST 7 E GEYSER              47.28N 110.35W
12/11/2018  M59 MPH          JUDITH BASIN       MT   OTHER FEDERAL

&&

MOLDAN

Event by event

2 high wind. Local standard time, as filed.

High Wind, Meagher

When: December 12, 1:20 AM MST
Where: Meagher forecast zone
Measured: 50 kt (58 mph) measured gust
Reported by: AWOS

High wind gust of 58 mph measured at awos 4 S White Sulpher Springs.

High Wind, Fergus

When: December 12, 1:52 AM MST
Where: Fergus forecast zone
Measured: 57 kt (66 mph) measured gust
Reported by: Mesonet

High wind gust measured 66 mph at mesonet 7 ESE Hilger.

What these are

High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.

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

The same day elsewhere

Every storm in Montana in 2018 Every state in 2018 This day in weather history Warnings in Montana, December 2018

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: 797092, 796687.