Mesoscale Discussion 1521

Issued

Aug 11, 2016, 1:35 PM MDT (19:35 UTC)

Expired

Aug 11, 2016, 4:00 PM MDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

20%

Counties Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes 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, Lawrence County, SD, Oglala Lakota County, SD, Pennington County, SD, Converse County, WY, Goshen County, WY, Niobrara County, WY, Weston County, WY

The Cheyenne radar (KCYS), 188 km from the middle of the area, began a volume at 19:34 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.

• Severe Thunderstorm Watch 444Aug 11, 5:30 PM MDT

935 
ACUS11 KWNS 111936
SWOMCD
SPC MCD 111935 
NEZ000-SDZ000-COZ000-WYZ000-112200-

MESOSCALE DISCUSSION 1521
NWS STORM PREDICTION CENTER NORMAN OK
0235 PM CDT THU AUG 11 2016

AREAS AFFECTED...ERN WY...SW SD...WRN NEB

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 111935Z - 112200Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A POTENTIAL FOR HAIL AND STRONG WIND GUSTS IS LIKELY TO
DEVELOP ACROSS ERN WY...WRN NEB AND SWRN SD OVER THE NEXT FEW HOURS.
THE THREAT IS EXPECTED TO BE TOO MARGINAL FOR WW ISSUANCE.

DISCUSSION...LATEST SFC ANALYSIS SHOWS A SFC LOW IN ERN NEB WITH A
SFC TROUGH EXTENDING NWD INTO ECNTRL SD. SFC WINDS TO THE WEST OF
THE TROUGH ARE FROM THE NORTH TO NORTHWEST ACROSS MUCH OF THE NRN
PLAINS. LOW-LEVEL CONVERGENCE APPEARS TO BE MAXIMIZED IN THE BLACK
HILLS WHERE THUNDERSTORMS ARE DEVELOPING AHEAD OF A VORTICITY MAX
MOVING THROUGH NE WY. A POCKET OF LOW-LEVEL MOISTURE IS IN PLACE
FROM NEAR THE BLACK HILLS SWD INTO WRN NEB WHERE SFC DEWPOINTS ARE
IN THE LOWER TO MID 60S F. THIS IS CONTRIBUTING TO MODERATE
INSTABILITY WITH MLCAPE VALUES IN THE 1000 TO 1500 J/KG RANGE. IN
ADDITION TO MODERATE INSTABILITY...THE LATEST WSR-88D VWP AT RAPID
CITY SHOWS 40 TO 50 KT OF WSW FLOW IN THE MID-LEVELS WHICH IS
HELPING TO CREATE ABOUT 40 KT OF 0-6 KM SHEAR. THIS ENVIRONMENT
SHOULD BE ENOUGH TO SUPPORT STORM ROTATION WITH THE MORE ROBUST
UPDRAFTS AND HAIL MAY OCCUR AS CELLS CONTINUE TO STRENGTHEN OVER THE
NEXT FEW HOURS. STEEPENING LOW-LEVEL LAPSE RATES LATE THIS AFTERNOON
MAY ALSO SUPPORT A FEW MARGINALLY SEVERE WIND GUSTS AS WELL.

..BROYLES/DARROW.. 08/11/2016

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

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

LAT...LON   44480484 43740583 43260605 43040600 42830568 42670502
            42290457 41560430 41260414 40930356 41130251 42290200
            43470219 44620326 44480484

Mesoscale Discussions in Nebraska, 2016Mesoscale Discussions in South Dakota, 2016Mesoscale Discussions in Wyoming, 2016Every mesoscale discussion in 2016

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.