Alert archive / Montana / Mesoscale Discussions in 2006

Mesoscale Discussion 913

May 20, 200618 counties in Montana; 4 counties in Wyoming

The Storm Prediction Center issued this mesoscale discussion at May 20, 2006, 6:04 PM MDT for 18 counties in Montana; 4 counties in Wyoming. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued: May 20, 2006, 6:04 PM MDT (00:04 UTC)
Expired: May 20, 2006, 7:30 PM MDT
In force: 86 min
Issued by: the Storm Prediction Center

All 22 counties

Big Horn County, MT, Carbon County, MT, Carter County, MT, Custer County, MT, Garfield County, MT, Golden Valley County, MT, McCone County, MT, Musselshell County, MT, Petroleum County, MT, Phillips County, MT, Powder River County, MT, Prairie County, MT, Rosebud County, MT, Stillwater County, MT, Sweet Grass County, MT, Treasure County, MT, Valley County, MT, Yellowstone County, MT, Campbell County, WY, Crook County, WY, Sheridan County, WY, Weston County, WY

The radar

The Billings radar (KBLX), 83 km from the middle of the area, began a volume at 00:04 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

Glasgow Intl Airport, MT (KGGW), launched 00:00Z, 0.1 hours before the alert went out and 249 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1714 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 165 m²/s²
0-3 km storm-relative helicity: 266 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
ACUS11 KWNS 210004
SWOMCD
SPC MCD 210004 
MTZ000-WYZ000-210130-

MESOSCALE DISCUSSION 0913
NWS STORM PREDICTION CENTER NORMAN OK
0704 PM CDT SAT MAY 20 2006

AREAS AFFECTED...SOUTH CENTRAL/EASTERN MT AND NORTHEAST WY

CONCERNING...SEVERE THUNDERSTORM WATCH 367...

VALID 210004Z - 210130Z

VALID PORTION OF SEVERE THUNDERSTORM WATCH 367 CONTINUES ACROSS
MT/FAR NORTHERN WY UNTIL 02Z...WITH CONTINUED THREAT FOR ISOLATED
LARGE HAIL/DAMAGING WINDS OVER THE NEXT FEW HOURS.

RELATIVELY WELL ORGANIZED LINE OF STRONG STORMS/MCS IS MOVING
EAST-NORTHEAST ACROSS EAST CENTRAL MT AT THIS TIME...FROM WESTERN
GARFIELD COUNTY INTO PHILLIPS COUNTY AS OF 2345Z. ALTHOUGH SHORT
TERM SEVERE THREAT MAY REMAIN...THIS LINE OF STORMS WILL QUICKLY
WEAKEN AS THEY PROGRESS EAST OF THE FRONT INTO A COOLER/MORE STABLE
AIRMASS PER NIL CAPE/STRONG CINH EVIDENT IN 00Z OBSERVED GLASGOW
RAOB. FARTHER SOUTH...AN ISOLATED SEVERE THREAT WILL ALSO PERSIST
OVER THE NEXT HOUR OR TWO FROM SOUTH CENTRAL MT INTO NORTHEAST
WY...WHERE THE AIRMASS REMAINS WEAKLY TO MODERATELY UNSTABLE OUTSIDE
OF CONVECTIVE OUTFLOWS /NAMELY ACROSS FAR SOUTHEAST MT INTO
NORTHEAST WY/. INDICATIONS ARE THAT WW 367 WILL BE ALLOWED TO EXPIRE
AS SCHEDULED AT 02Z WITH A DIMINISHING SEVERE THREAT VIA LOSS OF
DAYTIME HEATING AND/OR CONVECTIVELY OVERTURNED BOUNDARY LAYER.

..GUYER.. 05/21/2006

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...UNR...BYZ...GGW...RIW...TFX...

45291028 46310971 47570896 48710895 48660696 47660549
46260455 43630418 43720564 44800734 45020857

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 21, 2:09 PM MDT	Mesoscale Discussion	SPC	Big Horn, Carbon, Powder River, Stillwater, Yellowstone	2 hr
May 21, 1:20 PM MDT	Mesoscale Discussion	SPC	Goshen, Niobrara, Weston	115 min

Nearby

Mesoscale Discussions in Montana, 2006 Mesoscale Discussions in Wyoming, 2006 Every mesoscale discussion in 2006

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.