Winter Storm and Heavy Snow in Montana, April 11 to 12, 2020

Name: Winter Storm and Heavy Snow in Montana, April 11 to 12, 2020
Start: 2020-04-11T05:44
End: 2020-04-12T17:00
Location: Montana

April 11 to 12, 2020 · NWS TFX · 12 events in 8 counties and zones

A significant winter storm affects the region. Forecasts remain, generally, on track.

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 12

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.

A significant winter storm affects the region. Forecasts remain, generally, on track. Heaviest snow accumulation remains focused on the east slopes of The Rockies and along and to the north of The Little Belts. Total accumulations of 1 foot are forecast across areas of western Teton, NW Lewis and Clark, Judith Basin and Fergus counties near the mountains, where impacts to travel, agricultural and outdoor activities are greatest. Initial shift to northwesterly winds across the northern half of the forecast area with cooling behind the initial frontal feature a bit less aggressive than anticipated. Temperatures cooling to the 40s across the northern tier of the forecast area and to the 30s upstream over Alberta, and cooler temperatures gradually spread south into the |area. Onset of precipitation is somewhat nebulous with showers increasing through early evening before a more widespread surge of moisture and colder air moves south. Timing for heaviest precipitation across central MT shifted a bit later. While the arrival of snow and colder temperatures is somewhat slower, overall precipitation |amounts change little. Temperatures fall into the 20s for most areas north of I90, and locally high snowfall rates lead to icy or at least snow and slush covered roadways. Northerly to easterly winds increase with the arrival of colder air, creating areas of blowing and drifting snow in exposed areas. Steady or falling temperatures possibly reach as cold as the single digits in some locations.

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 Apr 11, 4:50 AM MST, 54 minutes earlier.

Area forecast discussion, Apr 11, 4:50 AM MST, 54 minutes before

Area Forecast Discussion
National Weather Service Great Falls MT
550 AM MDT Sat Apr 11 2020

Aviation Section Updated

.SYNOPSIS...
A cold front will continue to push southward through the region
today. Widespread snow will continue over North Central MT, while
rain, snow and isolated thunderstorms will be possible over
Southwest MT. The steady snow ends this evening, as cold
temperatures develop tonight. Several weather disturbances will
move through the region from Sunday through Thursday, resulting in
a very slow warming trend, along with scattered chances for rain
or snow showers.

&&

.DISCUSSION...
Today through Sunday...A cold front continues to push southward
through the region. At 4 AM, the cold front just moved through the
Helena area. The colder air should arrive south of I-90 after 8 AM
for most areas, thus the winter weather advisory was delayed until
then for Beaverhead, Madison and Gallatin counties. Otherwise,
the remainder of the winter highlights remain as is. Overall,
previous snowfall forecasts remain on track. Temperatures will not
rise much today over the north. It warms just enough ahead of the
cold front that an isolated thunderstorm will be possible this
afternoon, mainly south of a line from Dillon to Big Sky. For
tonight, the steady snow generally diminishes from north to south
before Midnight, with scattered snow showers after Midnight. Some
patchy fog develops after Midnight, and I did lower temperatures a
touch below NBM over North Central MT with some clearing skies
towards day break. Slightly warmer conditions move into the region
on Sunday, with only a small chance for a passing shower.

For Monday through Saturday, the flow aloft will generally remain
out of the north most days. As a result, numerous upper level
disturbances will move southward through this period. Right now,
Wednesday and Thursday look to have the highest chances for
precipitation. The airmass will continue to be cold enough that
snow will possible at all elevations, especially at night. A few
inches of snow will be possible with the system on Wednesday, and
winter highlight might be needed, especially for the mountains.
Expect a slow warming trend through Friday, with better warm up
possible on Saturday. Brusda

&&

.AVIATION...
Updated 550 AM MDT Sat Apr 11 2020 (12Z TAF Period)

Expect widespread snow to continue over Central MT and as rain/snow
over spread Southwest MT by 18z. An isolated afternoon thunderstorm
is possible, mostly south of a line from Dillon to Big Sky. IFR
conditions or lower is expected in snow today through 21z.
Conditions slowly improve from north to south after 21z, but snow is
likely to continue over Southwest/Central MT until about 12z Sunday.
Patchy dense fog could develop around 12z Sunday in areas that clear
out from Great Falls to Cut Bank. Mountains/passes will be obscured
through the period. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  29   2  29  12 / 100  70   0  20
CTB  23   4  30  12 / 100  20  10  10
HLN  33  10  33  12 / 100  70   0  10
BZN  43  13  31  10 / 100  80  10  10
WYS  40   7  28   2 /  90  60  10   0
DLN  46  13  31  13 / 100  80  10  10
HVR  28  10  33  14 /  90  20  20  10
LWT  31   3  23   8 / 100  80  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MDT tonight Broadwater...
Jefferson.

Winter Storm Warning until midnight MDT tonight Cascade...
Central and Southern Lewis and Clark...Chouteau...Meagher.

Winter Weather Advisory until 6 PM MDT this evening Blaine...
Hill...Liberty...Toole.

Winter Weather Advisory from 8 AM this morning to midnight MDT
tonight Beaverhead.

Winter Weather Advisory from 8 AM this morning to midnight MDT
tonight Gallatin...Madison.

Winter Storm Warning until midnight MDT tonight Fergus...Judith
Basin.

Winter Storm Warning until 6 PM MDT this evening Eastern
Glacier...Eastern Pondera...Eastern Teton...Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

&&

http://www.weather.gov/greatfalls

In the hours before

Local storm report, Apr 11, 3:41 AM MST, 2 hours 3 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
441 AM MDT SAT APR 11 2020

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

0200 AM     SNOW             HAVRE                   48.54N 109.68W
04/11/2020  E2.0 INCH        HILL               MT   NEWSPAPER

            ESTIMATED SNOWFALL OF 2 INCHES.

&&

BRUSDA

Local storm report, Apr 11, 4:52 AM MST, 52 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
552 AM MDT SAT APR 11 2020

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

0550 AM     SNOW             4 W HAVRE               48.54N 109.76W
04/11/2020  M3.8 INCH        HILL               MT   OFFICIAL NWS OBS

            3.8 INCHES AT THE HAVRE AIRPORT.

&&

BRUSDA

Local storm report, Apr 11, 5:30 AM MST, 14 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
630 AM MDT SAT APR 11 2020

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

0626 AM     HEAVY SNOW       CHOTEAU                 47.81N 112.19W
04/11/2020  E5.5 INCH        TETON              MT   TRAINED SPOTTER

            STILL LIGHTLY SNOWING.

&&

MM

Local storm report, Apr 11, 5:33 AM MST, 11 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
633 AM MDT SAT APR 11 2020

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

0633 AM     HEAVY SNOW       4 SSE BYNUM             47.93N 112.29W
04/11/2020  E5.6 INCH        TETON              MT   CO-OP OBSERVER

&&

MM

Local storm report, Apr 11, 5:35 AM MST, 9 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
635 AM MDT SAT APR 11 2020

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

0635 AM     HEAVY SNOW       JOPLIN                  48.56N 110.76W
04/11/2020  E4.0 INCH        LIBERTY            MT   TRAINED SPOTTER

&&

MM

Event by event

7 winter storm, 5 heavy snow. Local standard time, as filed.

Winter Storm, Eastern Glacier

When: April 11, 5:44 AM MST
Where: Eastern Glacier forecast zone
Reported by: Trained Spotter

Measured 6 inches at 13 ESE Browning.

Winter Storm, Fergus

When: April 11, 4:00 PM MST
Where: Fergus forecast zone
Reported by: Trained Spotter

Measured 8 inches of snow at 5 NE Hilger. Still snowing.

Winter Storm, Judith Basin

When: April 11, 5:00 PM MST
Where: Judith Basin forecast zone
Reported by: COOP Observer

Co-op observer station measured 6.2 inches snow at stnm8 Stanford.

Heavy Snow, Eastern Teton

When: April 11, 7:31 PM MST
Where: Eastern Teton forecast zone
Reported by: Public

Estimated 10 inches of new snow at the base and 14 inches at 7600 feet measured 23 SW Dupuyer. reported via twitter from Teton Pass Ski Resort. Station elevation: 6235 ft.

Heavy Snow, Southern Lewis and Clark

When: April 11, 7:45 PM MST
Where: Southern Lewis and Clark forecast zone
Reported by: Public

Report of 13 inches from Unionville, elevation 5000 feet. Reported via facebook.

Heavy Snow, Southern Lewis and Clark

When: April 11, 7:47 PM MST
Where: Southern Lewis and Clark forecast zone
Reported by: Trained Spotter

Snow measured 15 inches at 7 SW Helena. Previous measurement 4 inches at 9 AM. 11 inches of snow fell in 10 hours and 47 min.

Winter Storm, Eastern Teton

When: April 11, 8:00 PM MST
Where: Eastern Teton forecast zone
Reported by: Trained Spotter

Measured 8.5 inches at Choteau.

Heavy Snow, Gallatin

When: April 12, 6:48 AM MST
Where: Gallatin forecast zone
Reported by: Public

Measured 16 inches at 19 ESE Maudlow. Relayed via social media.

Winter Storm, Eastern Pondera

When: April 12, 7:00 AM MST
Where: Eastern Pondera forecast zone
Reported by: Public

Storm total snow from Friday evening through Sunday morning 9 inches. Reported via facebook. Report time and location are approximated.

Winter Storm, Cascade

When: April 12, 7:22 AM MST
Where: Cascade forecast zone
Reported by: Trained Spotter

Storm total snow 7 inches at 11 SSE Ulm. Measurements ranged from 6 to 8 inches due to blowing snow.

Heavy Snow, Southern Lewis and Clark

When: April 12, 9:46 AM MST
Where: Southern Lewis and Clark forecast zone
Reported by: Trained Spotter

Measured 17 inches at 7 SW Helena.

Winter Storm, Judith Basin

When: April 12, 5:00 PM MST
Where: Judith Basin forecast zone
Reported by: COOP Observer

Co-op observer station stnm8 stanford measured 9.4 inches. Storm total snowfall from Friday through Saturday night.

What these are

Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.
Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.

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

The same day elsewhere

Every storm in Montana in 2020 Every state in 2020 This day in weather history Warnings in Montana, April 2020

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: 889830, 889826, 889829, 889822, 889821, 889820, 889823, 889832, 889838, 889842, 889831, 889834.