Alert archive / Montana / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 117, NWS Billings, MT

August 21, 2002Custer County, Montana

NWS Billings, MT issued this severe thunderstorm warning at Aug 21, 2002, 9:37 AM MDT for Custer County, Montana. It was in force for 53 min. 1 report came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: Aug 21, 2002, 9:37 AM MDT (15:37 UTC)
Expired: Aug 21, 2002, 10:30 AM MDT
In force: 53 min
Issued by: NWS Billings, MT
Area: Whole counties

County Custer County, MT

The radar

The Glasgow radar (KGGW), 231 km from the middle of the area, began a volume at 15:41 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.

What was reported inside it

Time	Report	Where	Remark
Aug 21, 10:05 AM MDT	Hail 0.75	Miles City, MT

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

The nearest sounding before it

Glasgow Intl Airport, MT (KGGW), launched 12:00Z, 3.6 hours before the alert went out and 232 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 10 J/kg
Mixed-layer CIN: -496 J/kg
Mixed-layer LCL: 983 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: -50 m²/s²
0-3 km storm-relative helicity: -10 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

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

NWS Billings, MT wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 21, 9:10 AM MDT, 27 minutes earlier.

Area forecast discussion, Aug 21, 9:10 AM MDT, 27 minutes before

SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
ISSUED BY GLASGOW MT NWS
910 AM MDT WED AUG 21 2002

.SHORT TERM...VALID FOR TDY AND THU...

CONVECTIVE ACTIVITY HAS DEVELOPED ALONG A NORTHWEST TO SOUTHEAST
ORIENTED AXIS FROM NORTHERN ROSEBUD COUNTY INTO CUSTER COUNTY.
CONVECTION APPEARS TO BE ASSOCIATED WITH A WEAK SHORT WAVE MOVING
NORTHEAST OUT OF WYOMING. MESO-ETA DOING A GOOD JOB OF PICKING UP
AREA OF OMEGA AND RELATIVELY STEEP LAPSE RATES OVER CUSTER COUNTY.
SOME SHOWERS ALSO OCCURING ALONG THE EAST SLOPE OF THE BIG HORN
MOUNTAINS. MESO-ETA INDICATING A BRIEF REPRIEVE FROM CONVECTIVE
ACTIVITY OVER THE NEXT FEW HOURS. CONVECTION SHOULD INTENSIFY THIS
AFTERNOON AS 850-500MB LAPSE RATES INCREASE ABOVE 7 C/KM. ALTHOUGH
THUNDERSTORMS SHOULD DEVELOP ACROSS ENTIRE CWA...EXPECT STRONGEST
STORMS OVER THE EASTERN HALF OF THE CWA WHERE CAPES VALUES WILL
EXCEED 1000 J/KG BY 21Z. GOING FORECAST IN GOOD SHAPE. NO UPDATES.
POHL

.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE...

CONSISTENCY IN THE AVN SUPPORTS THE CHANGES MADE EARLIER IN THE DAY
KEEPING A RISK OF CONVECTION IN THE FORECAST THROUGH SUNDAY. PATTERN
BECOMES A BIT NEGATIVELY TILTED BY FRIDAY EVENING AND THIS CONTINUES
INTO SATURDAY. SURFACE PRESSURE PATTERNS DONT LOOK REAL SUPPORTIVE
FOR DEWPOINT ADVECTION INTO THE AREA BUT RETURN FLOW BEHIND THE EACH
DAYS CONVECTION COULD HELP KEEP THE LOW LEVEL AIRMASS MOIST. BORSUM

    TDY THU     FRI     SAT     SUN     MON     TUE
-------------------------------------------------------
BIL 083 056/085 054/084 052/086 054/086 053/083 051/082
    4/T 43/T    32/T    33/T    33/T    30/E    00/B
LVM 080 051/081 050/082 048/083 048/084 047/081 045/080
    4/T 43/T    33/T    33/T    33/T    30/E    00/B
HDN 085 055/087 052/087 050/088 052/088 050/085 048/084
    4/T 43/T    32/T    33/T    33/T    30/E    00/B
MLS 085 058/086 056/085 055/087 057/087 056/083 054/082
    4/T 42/T    22/T    33/T    33/T    30/E    00/B
4BQ 086 056/085 055/084 054/086 056/086 055/082 053/081
    4/T 42/T    22/T    33/T    33/T    30/E    00/B
BHK 083 055/083 053/083 052/084 053/084 053/080 051/079
    4/T 42/T    22/T    33/T    33/T    30/E    00/B
SHR 084 053/084 051/084 051/085 050/084 049/080 047/079
    4/T 43/T    33/T    33/T    33/T    30/E    00/B

.BYZ...
MT...NONE.
WY...NONE.

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 21, 4:41 PM MDT	Severe Thunderstorm Warning	BYZ	Musselshell	64 min
Aug 21, 5:24 PM MDT	Flash Flood Warning	BYZ	Musselshell	3 hr
Aug 21, 5:00 PM MDT	Severe Thunderstorm Warning	BYZ	Sheridan	60 min

Nearby

Severe Thunderstorm Warnings in Montana, 2002 Every severe thunderstorm warning in 2002

Sources

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