Alert archive / Montana / Snow Squall Warnings in 2021

Snow Squall Warning 1, NWS Missoula, MT

December 24, 2021Mineral County, Montana

NWS Missoula, MT issued this snow squall warning at Dec 24, 2021, 8:39 PM MST for Mineral County, Montana. It was in force for 81 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 24, 2021, 8:39 PM MST (03:39 UTC)
Expired
Dec 24, 2021, 10:00 PM MST
In force
81 min
Issued by
NWS Missoula, MT
Area
Storm-based polygon

County Mineral County, MT

The radar

The Missoula radar (KMSX), 135 km from the middle of the area, began a volume at 03:43 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 00:00Z, 3.7 hours before the alert went out and 61 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 00:00Z on 2021-12-25Temperature 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 00:00Z on 2021-12-25The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 187 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
864 m above ground
0-6 km bulk shear
51 kt
0-1 km storm-relative helicity
187 m²/s²
0-3 km storm-relative helicity
171 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

637 
WWUS55 KMSO 250339
SQWMSO

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Snow Squall Warning
National Weather Service Missoula MT
839 PM MST Fri Dec 24 2021

MTC061-250500-
/O.NEW.KMSO.SQ.W.0001.211225T0339Z-211225T0500Z/
Mineral MT-
839 PM MST Fri Dec 24 2021

The National Weather Service in Missoula has issued a

* Snow Squall Warning for...
  Northwestern Mineral County in west central Montana...

* Until 1000 PM MST.

* At 835 PM MST, a dangerous area of intense snow was located 39 
  miles southwest of Lookout Pass moving northeast at 35 mph. 
  Moderate snow will continue until 9:05 to 9:15 MST when this 
  intense band of snow is expected to arrive.

  HAZARD...Poor visibility in heavy snow.

  SOURCE...Radar indicated.

  IMPACT...Dangerous life-threatening travel.

I-90 from Lookout Pass and 10 miles east, approximately the first 
weigh station in Montana. 

Locations impacted include...
Lookout Pass.

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 4745 11572 4746 11570 4746 11568 4743 11562
      4741 11564
TIME...MOT...LOC 0335Z 239DEG 35KT 4751 11555 

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Dec 25, 8:23 AM MSTSpecial Weather StatementMSOMissoula52 min
Dec 25, 11:00 AM MSTWind Chill AdvisoryMSOFlathead, Lake7 hr
Dec 25, 11:00 AM MSTWinter Weather AdvisoryMSOFlathead, Lake6 hr
Dec 25, 12:43 PM MSTWinter Weather AdvisoryMSODeer Lodge, Flathead, Granite, Lake, Lincoln, Mineral and 5 more28 hr

Nearby

Snow Squall Warnings in Montana, 2021Every snow squall warning in 2021

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.