Alert archive / Nebraska / Mesoscale Discussions in 2016

Mesoscale Discussion 677

May 22, 201619 counties in Nebraska; 6 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 22, 2016, 1:54 PM MDT for 19 counties in Nebraska; 6 counties in South Dakota. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: May 22, 2016, 1:54 PM MDT (19:54 UTC)
Expired: May 22, 2016, 3:30 PM MDT
In force: 96 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 25 counties

Arthur County, NE, Blaine County, NE, Brown County, NE, Chase County, NE, Cherry County, NE, Dundy County, NE, Frontier County, NE, Grant County, NE, Hayes County, NE, Hitchcock County, NE, Hooker County, NE, Keith County, NE, Keya Paha County, NE, Lincoln County, NE, Logan County, NE, McPherson County, NE, Perkins County, NE, Red Willow County, NE, Thomas County, NE, Jones County, SD, Lyman County, SD, Mellette County, SD, Stanley County, SD, Todd County, SD, Tripp County, SD

The radar

The North Platte radar (KLNX), 43 km from the middle of the area, began a volume at 19:57 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

N. Platte/Lee Bi, NE (KLBF), launched 12:00Z, 7.9 hours before the alert went out and 131 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: 902 J/kg
Mixed-layer CIN: -195 J/kg
Mixed-layer LCL: 591 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 299 m²/s²
0-3 km storm-relative helicity: 499 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

627 
ACUS11 KWNS 221954
SWOMCD
SPC MCD 221954 
SDZ000-NEZ000-222130-

MESOSCALE DISCUSSION 0677
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT SUN MAY 22 2016

AREAS AFFECTED...PORTIONS OF CNTRL/WRN NEB...S-CNTRL SD

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 221954Z - 222130Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...ISOLATED TO WIDELY-SCATTERED THUNDERSTORM DEVELOPMENT IS
EXPECTED LATER THIS AFTERNOON. SUPERCELLS CAPABLE OF LARGE
HAIL...DAMAGING WIND...AND A COUPLE OF TORNADOES WILL BE POSSIBLE.
WATCH ISSUANCE WILL LIKELY BE REQUIRED BY 21Z.

DISCUSSION...AT 1930Z...SLOWLY DEEPENING CU WAS NOTED ALONG A WEAK
SFC BOUNDARY DRAPED FROM WRN NEB INTO S-CNTRL SD...WITH CG ACTIVITY
RECENTLY NOTED ACROSS CHERRY COUNTY. SOME CU WAS ALSO NOTED ALONG A
DRYLINE NEAR THE NE/CO/KS BORDERS. THE THERMODYNAMIC ENVIRONMENT
ACROSS THIS AREA...AS SAMPLED BY THE 18Z LBF SOUNDING...IS
CHARACTERIZED BY STEEP MIDLEVEL LAPSE RATES AND MODERATE BUOYANCY.
THE MODIFIED LBF SOUNDING YIELDS MLCAPE OF AROUND 2000 J/KG...WHICH
IS IN AGREEMENT WITH RECENT MESOANALYSIS ESTIMATES. THE OBSERVED
WIND PROFILE FROM THE SOUNDING AND LNX VWP INDICATES FAVORABLE
EFFECTIVE HELICITY OF AROUND 150-200 M2/S2...THOUGH DEEP-LAYER SHEAR
IS RELATIVELY WEAK AND SOME UNFAVORABLE BACKING OF THE MIDLEVEL FLOW
WAS NOTED AS WELL. 

IT APPEARS THAT A WEAK VORT MAX IS APPROACHING SW NEB...BUT IT IS
UNCLEAR IF THIS FEATURE WILL BE SUFFICIENT TO INITIATE AND SUSTAIN
DEEP CONVECTION...GIVEN SOME RESIDUAL CAPPING AND VERY DRY AIR ALOFT
NOTED ON THE LBF SOUNDING. LATE THIS AFTERNOON...ASCENT WILL BEGIN
TO INCREASE AHEAD OF A STRONGER UPPER TROUGH CURRENTLY MOVING EWD
OUT OF THE GREAT BASIN...WITH INCREASING CONVECTIVE COVERAGE
EXPECTED IN THE 22-00Z TIME FRAME.

ONCE INITIATION OCCURS...SUPERCELLS CAPABLE OF LARGE HAIL AND
DAMAGING WINDS WILL BE POSSIBLE. SOME TORNADO RISK WILL ALSO
EXIST...ESPECIALLY ACROSS THE SRN PART OF THE MCD AREA...WHERE
LOW-LEVEL WINDS WILL BE A LITTLE MORE BACKED IN RESPONSE TO
DEEPENING LOW PRESSURE OVER ERN CO. STORM MODE MAY BECOME
INCREASINGLY MIXED WITH NWD EXTENT GIVEN THE PRESENCE OF BACKED
MIDLEVEL FLOW...BUT INSTABILITY/SHEAR WILL STILL BE SUFFICIENT FOR A
SEVERE RISK EXTENDING INTO CNTRL SD.

..DEAN/HART.. 05/22/2016

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

ATTN...WFO...FSD...ABR...GID...LBF...UNR...GLD...

LAT...LON   40900196 41460220 42940143 44630092 44400026 44129963
            43419919 42399948 40040028 40010196 40900196

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 22, 2:20 PM MDT	Tornado Watch	SPC	Arthur, Blaine, Brown, Cherry, Custer, Deuel and 10 more	7 hr
May 22, 4:45 PM MDT	Mesoscale Discussion	SPC	Hitchcock	2 hr
May 22, 5:20 PM MDT	Severe Thunderstorm Watch	SPC	Chase, Dawson, Dundy, Frontier, Furnas, Gosper and 4 more	6 hr
May 22, 5:35 PM MDT	Mesoscale Discussion	SPC	Arthur, Cherry, Deuel, Garden, Grant, Hooker and 8 more	115 min
May 22, 2:57 PM MDT	Mesoscale Discussion	SPC	Campbell, Corson, Dewey, Edmunds, Faulk, McPherson and 4 more	93 min
May 22, 4:21 PM MDT	Severe Thunderstorm Watch	SPC	Brown, Buffalo, Campbell, Corson, Dewey, Edmunds and 7 more	8 hr

Nearby

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

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.