Mesoscale Discussion 923

Issued

May 27, 2012, 2:58 PM CDT (19:58 UTC)

Expired

May 27, 2012, 4:00 PM CDT

In force

62 min

Issued by

the Storm Prediction Center

Chance of a watch

95%

The Omaha radar (KOAX), 74 km from the middle of the area, began a volume at 19:58 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 304May 27, 3:45 PM CDT
• Severe Thunderstorm Watch 307May 27, 6:10 PM CDT

012 
ACUS11 KWNS 271959
SWOMCD
SPC MCD 271958
IAZ000-MNZ000-NEZ000-SDZ000-272100-

MESOSCALE DISCUSSION 0923
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SUN MAY 27 2012

AREAS AFFECTED...NE...SD...IA...MN

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 271958Z - 272100Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...A WATCH WILL BE ISSUED ACROSS PORTIONS OF ERN NEB...WRN
IA...AND POSSIBLY SWRN PORTIONS OF MN WITHIN THE NEXT HOUR.
CONDITIONS ALONG A COLD FRONT MOVING INTO THESE AREAS SHOULD SUPPORT
SEVERE TSTM DEVELOPMENT THROUGH THE REST OF THE AFTERNOON AND INTO
THE EVENING.

DISCUSSION...SFC ANALYSIS AT 19Z PLACES A NEARLY STALLED COLD FRONT
ALONG A LINE FROM MOX IN EXTREME SWRN MN TO LRJ IN NWRN IA TO OFK IN
NERN NEB. FRONTAL ZONE CONTINUES ALONG A SWWD LINE TO A TRIPLE-POINT
LOW AND DRYLINE ON THE KS/NEB BORDER...ESE OF MCK. WHEN CURRENT SFC
CONDITIONS ARE USED TO MODIFY 18Z OBSERVED SOUNDINGS FROM BOTH TOP
AND OAX...ALL INDICATIONS POINT TO THE INITIATION OF DEEP CONVECTION
WITHIN ANOTHER HOUR OR SO. THIS SCENARIO IS ALSO SUPPORTED BY THE
LATEST RR AND HRRR MODELS AND IS CONSISTENT WITH EARLIER SREF
GUIDANCE. /NOTE: ANOTHER MCD WILL BE ISSUED SHORTLY FOR TSTM
POTENTIAL FROM KS TO OK./

DEEP-LAYER VERTICAL SHEAR MAGNITUDES ON THE ORDER OF 40KT AND MLCAPE
IN THE 1200-1800 J/KG RANGE WILL CONTRIBUTE TO ROBUST AND ORGANIZED
STORM DEVELOPMENT. REMOVAL OF REMAINING INHIBITION ALONG THE FRONT
WILL OCCUR AS DEEP-LAYER ASCENT OVERSPREADS THE REGION THROUGH THE
EVENING. THIS SHOULD RESULT IN A SIGNIFICATION INCREASE IN STORMS
ALONG THE FRONT AND NEAR THE TRIPLE LOW. AREAL COVERAGE OF THIS
ROBUST DEVELOPMENT LENDS CONFIDENCE IN SEVERE WEATHER...ESPECIALLY
LARGE HAIL AND DAMAGING WINDS. TORNADO POTENTIAL IS A BIT MORE
UNCERTAIN GIVEN RELATIVELY HIGH CLOUD BASES....VEERED LOW LEVEL FLOW
AHEAD OF THE FRONT...AND DEEP-LAYER UNIDIRECTIONAL WIND PROFILES
EVIDENT IN SOUNDINGS AND VWP/PROFILER DATA ACROSS THE REGION. THESE
LIMITATIONS...HOWEVER...CAN BE OFFSET TO SOME DEGREE BY UPDRAFT
STRETCHING...STORM INTERACTIONS...AND THE POTENTIAL FOR VERY
LOCALIZED AREAS TO EXPERIENCE ENHANCED SR FLOW/HELICITY...SUCH AS
NEAR THE TRIPLE POINT LOW. TORNADO THREAT IS ALSO LIKELY GREATER
NEARER THE SURFACE LOW AND WARM FRONT IN MN WHERE ANOTHER WATCH MAY
BE NEEDED SHORTLY AFTER THIS INITIAL WATCH.

..CARBIN.. 05/27/2012

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

ATTN...WFO...MPX...DMX...FSD...OAX...GID...LBF...

LAT...LON   43239694 43969633 44179581 43859447 43489394 42769443
            42279491 41719544 41109591 40649622 40299658 40189688
            40069750 40079784 40079841 40099880 40249930 40489979
            40739993 41289962 41599914 42299812 42739747 43239694

Mesoscale Discussions in Nebraska, 2012Mesoscale Discussions in Iowa, 2012Mesoscale Discussions in Minnesota, 2012Every mesoscale discussion in 2012

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.