Alert archive / Montana / Snow Squall Warnings in 2023

Snow Squall Warning 2, NWS Missoula, MT

March 2, 2023Flathead County, Lincoln County, Sanders County, Montana

NWS Missoula, MT issued this snow squall warning at Mar 2, 2023, 6:31 PM MST for Flathead County, Lincoln County, Sanders County, Montana. It was in force for 29 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
Mar 2, 2023, 6:31 PM MST (01:31 UTC)
Expired
Mar 2, 2023, 7:00 PM MST
In force
29 min
Issued by
NWS Missoula, MT
Area
Storm-based polygon

Counties Flathead County, MT, Lincoln County, MT, Sanders County, MT

The radar

The Missoula radar (KMSX), 123 km from the middle of the area, began a volume at 01:35 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, 1.5 hours before the alert went out and 128 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 2023-03-03Temperature 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°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Spokane, WA at 00:00Z on 2023-03-03The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 149 square meters per square second.1939587897117Sfc1 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
1430 m above ground
0-6 km bulk shear
78 kt
0-1 km storm-relative helicity
149 m²/s²
0-3 km storm-relative helicity
66 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

632 
WWUS55 KMSO 030131
SQWMSO

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Snow Squall Warning
National Weather Service Missoula MT
631 PM MST Thu Mar 2 2023

MTC029-053-089-030200-
/O.NEW.KMSO.SQ.W.0002.230303T0131Z-230303T0200Z/
Lincoln MT-Sanders MT-Flathead MT-
631 PM MST Thu Mar 2 2023

The National Weather Service in Missoula has issued a

* Snow Squall Warning for...
  South central Lincoln County in northwestern Montana...
  North central Sanders County in northwestern Montana...
  Southwestern Flathead County in northwestern Montana...

* Until 700 PM MST.

* At 631 PM MST, a dangerous snow squall was located along a line
  extending from 32 miles west of Kalispell to 28 miles northeast of
  Thompson Falls, moving east at 45 mph.

  HAZARD...Flash freeze on roads. Intense bursts of heavy snow. 
           Gusty winds leading to blowing snow and visibility 
           rapidly falling to less than one-quarter mile. Wind gusts 
           up to 35 mph.

  SOURCE...Radar and webcams.

  IMPACT...Travel will become difficult and potentially dangerous 
           within minutes.

This includes Highway 2 between mile markers 72 and 96.
 
Locations impacted include...
Happys Inn and Bend. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Wet roadways will quickly freeze. Black ice will cause roads,
bridges, and overpasses to become slick and dangerous. Slow down and
be prepared for a sudden loss of traction.

Slow Down! Rapid changes in visibility and road conditions are
expected with this dangerous snow squall. Be alert for sudden
whiteout conditions.

Reduce speed and turn on headlights! During snow squalls, the
visibility may suddenly drop to near zero in whiteout conditions.

&&

LAT...LON 4805 11453 4788 11452 4787 11515 4813 11514
      4812 11472 4805 11467
TIME...MOT...LOC 0131Z 271DEG 38KT 4809 11499 4793 11499 

SNOW SQUALL...OBSERVED

$$

What forecasters said that day

The local office's own words before this snow squall warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Missoula, MT wrote its last area forecast discussion before this snow squall warning went out at Mar 2, 5:06 PM MST, 1 hour 25 minutes earlier.

Area forecast discussion, Mar 2, 5:06 PM MST, 1 hour 25 minutes before
Area Forecast Discussion National Weather Service Missoula MT 214 PM
MST Thu Mar 2 2023

.DISCUSSION...Snow showers are present across the region with
winds from the southwest in and along a cold frontal passage. The
showers will briefly lower visibilities as they pass. Winds will to
gust 35 to 40 mph in higher elevations while many valleys will
receive gusts 15 to 25 mph. Temperatures will cool below freezing
for all elevations after sunset, setting the stage for valleys to
see minor snowfall accumulations onto roadways. Valley accumulations
will be favored across southern portions of the Seeley-Swan Valley,
and Mission Valleys, and areas south and east of Missoula.

On Friday, west winds and convective snow showers will continue and
surface winds will trend weaker than Thursday. Snow showers will
produce localized areas of heavy snow, leading to brief periods of
slick and highly changeable driving conditions, even with higher sun
angles of early March.

Saturday will begin with a brief break in the active weather. By the
afternoon, a cold front from east of the Continental Divide will
begin to affect northwest Montana, primarily along US Highway 2 near
Marias Pass. There is moderate confidence for this front to move
across the Flathead Valley and Southwest Montana. Lower confidence
exists for the front to reach into the rest of western Montana.

The longwave trough over much of the western U.S. will persist
through much of next week. The unstable cold air mass will bring
snow showers across the entire Northern Rockies each day.
Temperatures will be 10 to 20 degrees colder than normal through
much of next week. This translates to high temps in the 30s and lows
in the teens.

&&

.AVIATION...A cold front will move through the Northern Rockies
tonight and Friday. Increased instability and cold air will result
in vicinity snow showers with gusty outflow winds 25-35 mph at all
terminals through 03/2300z.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...     Winter Weather Advisory until 8 PM MST Friday for West
Glacier      Region.

     Winter Weather Advisory until 8 PM MST Friday for Lower Clark
     Fork Region.

ID...Winter Weather Advisory until 7 PM PST Friday for Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&

In the hours before

Special weather statement, Mar 2, 5:46 PM MST, 45 minutes before
Special Weather Statement
National Weather Service Missoula MT
546 PM MST Thu Mar 2 2023

MTZ001-004-030130-
Lower Clark Fork Region MT-Kootenai/Cabinet Region MT-
546 PM MST Thu Mar 2 2023

...Intense snow showers will impact portions of southeastern Lincoln,
northwestern Sanders and western Flathead Counties through 630 PM
MST...

At 546 PM MST, Doppler radar was tracking intense snow showers along
a line extending from 17 miles south of Libby to 8 miles southwest of
Noxon. Movement was east at 35 mph.

HAZARD...Visibility one-half mile or less and winds in excess of 30
         mph.

SOURCE...Radar indicated.

IMPACT...Low visibility could result in dangerous driving
         conditions. Gusty winds could knock down tree limbs and
         blow around unsecured objects.

Locations impacted include...
Noxon, Tuscor, White Pine, Trout Creek and Happys Inn.

This includes the following highways...
 Highway 2 between mile markers 38 and 74.
 Highway 200 W between mile markers 12 and 38.

LAT...LON 4838 11492 4769 11528 4781 11585 4783 11585
      4785 11588 4785 11591 4829 11567
TIME...MOT...LOC 0046Z 279DEG 32KT 4815 11571 4789 11590

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH
Special weather statement, Mar 2, 5:49 PM MST, 42 minutes before
Special Weather Statement
National Weather Service Missoula MT
549 PM MST Thu Mar 2 2023

MTZ004-030115-
Lower Clark Fork Region MT-
549 PM MST Thu Mar 2 2023

...Intense snow showers will impact portions of east central Mineral,
west central Missoula and southeastern Sanders Counties through 615
PM MST...

At 548 PM MST, Doppler radar was tracking intense snow showers along
a line extending from 7 miles south of St. Regis to 20 miles
southwest of Superior. Movement was east at 60 mph.

HAZARD...Visibility one-half mile or less and winds in excess of 30
         mph.

SOURCE...Radar indicated.

IMPACT...Low visibility could result in dangerous driving
         conditions. Gusty winds could knock down tree limbs and
         blow around unsecured objects. Roads could become very
         slick due to melting and re-freezing of snow.

Locations impacted include...
Superior, Riverbend, Tarkio, Keystone, Lozeau, Quartz, Cyr and Stark.

This includes Interstate 90 between mile markers 35 and 73.

LAT...LON 4728 11506 4728 11434 4699 11451 4697 11505
      4700 11507 4702 11507 4704 11509 4706 11512
      4708 11514
TIME...MOT...LOC 0048Z 264DEG 51KT 4719 11509 4699 11522

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH

The office that day

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

IssuedProductOfficeCountiesLasted
Mar 2, 5:46 PM MSTSpecial Weather StatementMSOSanders44 min
Mar 2, 5:49 PM MSTSpecial Weather StatementMSOMineral26 min
Mar 2, 6:28 PM MSTSnow Squall WarningMSOFlathead47 min
Mar 2, 6:55 PM MSTSpecial Weather StatementMSOLincoln35 min
Mar 2, 7:02 PM MSTSpecial Weather StatementMSOMissoula43 min
Mar 2, 7:14 PM MSTSpecial Weather StatementMSOLake46 min
Mar 2, 7:26 PM MSTSpecial Weather StatementMSOMissoula49 min
Mar 2, 7:46 PM MSTSpecial Weather StatementMSO44 min
Mar 2, 7:57 PM MSTSpecial Weather StatementMSOMissoula48 min
Mar 2, 8:12 PM MSTSnow Squall WarningMSOMissoula, Ravalli48 min
Mar 2, 8:40 PM MSTSpecial Weather StatementMSOMineral35 min
Mar 2, 8:42 PM MSTSpecial Weather StatementMSOLake33 min
Mar 2, 9:08 PM MSTSpecial Weather StatementMSOPowell52 min
Mar 2, 9:33 PM MSTSpecial Weather StatementMSOMissoula42 min
Mar 2, 10:17 PM MSTSpecial Weather StatementMSOPowell58 min

Nearby

Snow Squall Warnings in Montana, 2023Every snow squall warning in 2023

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.