Alert archive / Montana / Snow Squall Warnings in 2020

Snow Squall Warning 13, NWS Missoula, MT

December 22, 2020Flathead County, Montana

NWS Missoula, MT issued this snow squall warning at Dec 22, 2020, 10:11 AM MST for Flathead County, Montana. It was in force for 34 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Dec 22, 2020, 10:11 AM MST (17:11 UTC)
Expired
Dec 22, 2020, 10:45 AM MST
In force
34 min
Issued by
NWS Missoula, MT
Area
Storm-based polygon

County Flathead County, MT

The radar

The Missoula radar (KMSX), 136 km from the middle of the area, began a volume at 17:09 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Spokane, WA (KOTX), launched 12:00Z, 5.2 hours before the alert went out and 167 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Spokane, WA at 12:00Z on 2020-12-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Spokane, WA at 12:00Z on 2020-12-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 93 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1198 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
93 m²/s²
0-3 km storm-relative helicity
71 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

547 
WWUS55 KMSO 221713
SQWMSO

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Snow Squall Warning
National Weather Service Missoula MT
1011 AM MST Tue Dec 22 2020

MTC029-221745-
/O.NEW.KMSO.SQ.W.0013.201222T1711Z-201222T1745Z/
Flathead MT-
1011 AM MST Tue Dec 22 2020

The National Weather Service in Missoula has issued a

* Snow Squall Warning for...
  Central Flathead County in northwestern Montana...

* Until 1045 AM MST.

* At 1011 AM MST, a dangerous area of intense snow was located over
  Evergreen, moving south at 10 mph.

  HAZARD...Extremely poor visibility in heavy snow and blowing snow. 
           Wind gusts greater than 30 mph.

  SOURCE...Radar indicated.

  IMPACT...Dangerous life-threatening travel.

* Kalispell...Highway 93

Locations impacted include...
Kalispell, Evergreen, Columbia Falls, La Salle and Somers. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Consider avoiding or delaying travel until the snow squall passes
your location. If you must travel, use extra caution and allow extra
time. Rapid changes in visibility and slick road conditions may lead
to accidents.

&&

LAT...LON 4837 11439 4837 11416 4806 11416 4806 11442
TIME...MOT...LOC 1711Z 005DEG 9KT 4824 11429 

$$
2 follow-up statements
454 
WWUS55 KMSO 221732
SQWMSO

Snow Squall Warning
National Weather Service Missoula MT
1031 AM MST Tue Dec 22 2020

MTC029-221745-
/O.CON.KMSO.SQ.W.0013.000000T0000Z-201222T1745Z/
Flathead MT-
1031 AM MST Tue Dec 22 2020

...A SNOW SQUALL WARNING REMAINS IN EFFECT UNTIL 1045 AM MST FOR
CENTRAL FLATHEAD COUNTY...

At 1031 AM MST, a dangerous snow squall was located near Kalispell,
moving south at 10 mph.

HAZARD...Extremely poor visibility in heavy snow and blowing snow. 
         Wind gusts greater than 30 mph.

SOURCE...Radar and webcams.

IMPACT...Dangerous life-threatening travel.

Highway 93 Kalispell to Somers

Locations impacted include...
Kalispell, Evergreen, La Salle and Somers. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Consider avoiding or delaying travel until the snow squall passes
your location. If you must travel, use extra caution and allow extra
time. Rapid changes in visibility and slick road conditions may lead
to accidents.

&&

LAT...LON 4833 11438 4833 11417 4806 11416 4806 11442
TIME...MOT...LOC 1731Z 002DEG 9KT 4814 11429 

$$
455 
WWUS55 KMSO 221743
SQWMSO

Snow Squall Warning
National Weather Service Missoula MT
1042 AM MST Tue Dec 22 2020

MTC029-221752-
/O.EXP.KMSO.SQ.W.0013.000000T0000Z-201222T1745Z/
Flathead MT-
1042 AM MST Tue Dec 22 2020

...THE SNOW SQUALL WARNING FOR CENTRAL FLATHEAD COUNTY WILL EXPIRE AT
1045 AM MST...

The snow squall which prompted the warning continues to move south. 
Therefore, the snow squall warning will be allowed to expire. Low 
visibility and Snow and ice-covered roads will continue to make 
travel difficult.

LAT...LON 4833 11438 4833 11417 4806 11416 4806 11442
TIME...MOT...LOC 1742Z 005DEG 9KT 4812 11429 

$$

The office that day

Everything else NWS Missoula, MT issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 22, 10:39 AM MSTSnow Squall WarningMSOFlathead, Lake36 min
Dec 22, 4:06 PM MSTSnow Squall WarningMSOGranite, Missoula, Powell84 min

Nearby

Snow Squall Warnings in Montana, 2020Every snow squall warning in 2020

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.