Mesoscale Discussion 920

Issued

May 21, 2006, 1:20 PM MDT (19:20 UTC)

Expired

May 21, 2006, 3:15 PM MDT

In force

115 min

Issued by

the Storm Prediction Center

Counties Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Deuel County, NE, Garden County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sheridan County, NE, Sioux County, NE, Custer County, SD, Fall River County, SD, Goshen County, WY, Niobrara County, WY, Weston County, WY

The Rapid City radar (KUDX), 177 km from the middle of the area, began a volume at 19:24 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.

000 
ACUS11 KWNS 211920
SWOMCD
SPC MCD 211920 
NEZ000-SDZ000-COZ000-WYZ000-212115-

MESOSCALE DISCUSSION 0920
NWS STORM PREDICTION CENTER NORMAN OK
0220 PM CDT SUN MAY 21 2006

AREAS AFFECTED...EASTERN WY/WESTERN NEB/FAR SOUTHWEST SD/FAR
NORTHEAST CO

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 211920Z - 212115Z

AT LEAST AN ISOLATED SEVERE THREAT IS EXPECTED TO INCREASE THIS
AFTERNOON AS STORMS DEVELOP EASTWARD FROM THE EASTERN WY/CO FRONT
RANGE INTO WESTERN NEB/FAR SOUTHWEST SD/NORTHEAST CO. ALTHOUGH
QUESTIONS REMAIN REGARDING POTENTIAL SEVERITY/EXTENT...A SEVERE
THUNDERSTORM WATCH COULD BE NEEDED BY 20Z-21Z.

EXTENSIVE CUMULUS CONTINUES TO STEADILY BUILD ACROSS THE CO/WY
MOUNTAINS EARLY THIS AFTERNOON...WITH RECENT THUNDERSTORM
DEVELOPMENT FROM NEAR DOUGLAS TO CHEYENNE WY. WATER VAPOR IMAGERY
SUGGESTS ONE OR MORE SUBTLE IMPULSES MAY BE EMBEDDED WITHIN BELT OF
MODERATE FLOW AMIDST UPPER RIDGE. WITH TIME...STORMS APPEAR LIKELY
TO DEVELOP/SPREAD EASTWARD ACROSS FAR EASTERN WY/NORTHEAST CO AND
EVENTUALLY INTO FAR SOUTHWEST SD/WESTERN NEB BY LATE
AFTERNOON/EVENING. POTENTIAL FOR AT LEAST ISOLATED SEVERE SHOULD
INCREASE ACCORDINGLY AS STRONG INSOLATION AND GENERAL MAINTENENCE OF
LOWER 50S F DEWPOINTS CONTRIBUTE TO MODERATE INSTABILITY ACROSS THE
CENTRAL HIGH PLAINS. LATEST RUC GUIDANCE SUGGESTS POTENTIAL FOR
1000-1250 J/KG MLCAPE LATER THIS AFTERNOON.

ALTHOUGH INITIALLY RATHER WEAK...VERTICAL SHEAR WILL LIKELY INCREASE
AS EASTERLY LOW LEVEL UPSLOPE COMPONENT INCREASES BY LATE AFTERNOON.
ADEQUATE DEGREE OF INSTABILITY/SHEAR MAY BE SUPPORTIVE OF SOME
SUPERCELL STRUCTURES...ALTHOUGH ORGANIZED MULTICELL CLUSTERS SHOULD
BE PREDOMINANT. LARGE HAIL WILL LIKELY BE THE PRIMARY HAZARD
INITIALLY...WITH POTENTIAL FOR DAMAGING WINDS ALSO DEVELOPING LATER
THIS AFTERNOON/EARLY EVENING VIA COLD POOLS /GIVEN LARGE T-TD
SPREADS/ AND POTENTIAL ORGANIZATION OF ONE OR MORE MCS CLUSTERS.

..GUYER.. 05/21/2006

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

ATTN...WFO...LBF...UNR...BOU...CYS...

43970485 44140405 42450174 41000215 40630410 42670480

Mesoscale Discussions in Nebraska, 2006Mesoscale Discussions in Wyoming, 2006Mesoscale Discussions in South Dakota, 2006Every mesoscale discussion in 2006

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.