Mesoscale Discussion 889

Issued

May 24, 2012, 1:34 PM CDT (18:34 UTC)

Expired

May 24, 2012, 3:30 PM CDT

In force

116 min

Issued by

the Storm Prediction Center

Chance of a watch

80%

The La Crosse radar (KARX), 61 km from the middle of the area, began a volume at 18:35 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.

• Tornado Watch 295May 24, 2:25 PM CDT
• Severe Thunderstorm Watch 296May 24, 3:35 PM CDT

210 
ACUS11 KWNS 241834
SWOMCD
SPC MCD 241834 
MIZ000-WIZ000-IAZ000-MNZ000-242030-

MESOSCALE DISCUSSION 0889
NWS STORM PREDICTION CENTER NORMAN OK
0134 PM CDT THU MAY 24 2012

AREAS AFFECTED...PORTIONS NERN IA...SERN MN...WRN/NRN WI...WRN UPPER
PENINSULA OF MI.

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

VALID 241834Z - 242030Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...SVR POTENTIAL FCST TO INCREASE OVER DISCUSSION AREA
THROUGH REMAINDER AFTERNOON AS INFLOW-LAYER PARCELS BECOME
ESSENTIALLY SFC-BASED FOR CONVECTION ALONG AND E OF FRONT/BOUNDARY
DESCRIBED BELOW.  THREAT THEN WILL SHIFT EWD ACROSS WI AS EMBEDDED
CONVECTION MOVES RAPIDLY TOWARD NNE TO NE.  MAIN CONCERN IS DAMAGING
WIND...WITH SPORADIC HAIL ALSO LIKELY.  TORNADO THREAT IS MORE
CONDITIONAL UPON STORM-SCALE PROCESSES WITH EMBEDDED MESOVORTICES.

DISCUSSION...18Z SFC MESOANALYSIS DEPICTED LOW NEAR FBL...WITH COLD
FRONT SSWWD ACROSS N-CENTRAL/SWRN IA.  COLD FRONT WILL CONTINUE
ESEWD OVER NRN/CENTRAL IA THROUGH AFTERNOON.  SHARPLY DEFINED
MESOSCALE BOUNDARY -- RELATED TO PRECIP AND DIFFERENTIAL HEATING --
CURVED FROM LOW ENEWD ACROSS SERN MN THEN NNEWD TO JUST NW
EAU...TOWARD ERN APOSTLE ISLANDS WI. SRN PORTION OF THIS BOUNDARY
HAS MOVED NWD FROM IA NEARLY IN STEP WITH TRANSLATION OF SFC
LOW...WHILE WI PORTIONS HAS BECOME QUASISTATIONARY.  HOWEVER...AIR
MASS W OF BOUNDARY OVER WI US QUITE STABLE.  THIS REGIME...ALONG
WITH AXIS OF SFC PRESSURE FALLS NEARLY COLLOCATED WITH
BOUNDARY...INDICATE LOW WILL MOVE ALONG BOUNDARY NNEWD OVER NWRN WI.
 MOISTURE CHANNEL IMAGERY INDICATES PLUME OF LARGE-SCALE/MID-UPPER
ASCENT...IMMEDIATELY PRECEDING EJECTING VORTICITY AXIS OVER SRN IA
AND NRN MN...AND FOLLOWED BY PRONOUNCED DRY SLOT ALOFT.  RELATED
DESTABILIZATION ALOFT APPEARS TO BE CONTRIBUTING TO INCREASE IN
CONVECTION OVER POST-FRONTAL AIR IN MN/IA...SOME OF WHICH IS NEARING
WARM SECTOR.

AIR MASS AHEAD OF FRONT AND BOUNDARY IS FCST TO CONTINUE
HEATING/DESTABILIZING...WITH SFC TEMPS IN UPPER 80S F AND DEW POINTS
UPPER 50S TO AROUND 60 LEADING TO MINIMAL MLCINH.  THIS...COMBINED
WITH FRONTAL/BOUNDARY LIFT...WILL LEAD TO BAND OF SFC-BASED TSTMS. 
DAMAGING WIND POTENTIAL SHOULD INCREASE RAPIDLY ONCE THAT
OCCURS...GIVEN STG DEEP-LAYER WINDS CONTRIBUTING TO 60-70 KT
EFFECTIVE SHEAR MAGNITUDES.  DEEP-LAYER MEAN FLOW AND SHEAR VECTORS
ARE NEARLY PARALLEL TO...BUT SLIGHTLY RIGHTWARD OF...WI BOUNDARY. 
MAIN MODE SHOULD BE QUASI-LINEAR...BUT WITH EMBEDDED LEWPS...SMALL
BOWS AND MESOVORTICES POSSIBLE.  EFFECTIVE SRH 200-300
J/KG...SHIFTING NEWD FROM NERN IA...ALSO INDICATES AT LEAST
TRANSIENT SUPERCELLULAR STRUCTURES POSSIBLE WITH ANY TSTMS THAT CAN
REMAIN RELATIVELY DISCRETE.

..EDWARDS/WEISS.. 05/24/2012

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

ATTN...WFO...MQT...GRB...MKX...DVN...DLH...ARX...MPX...DMX...

LAT...LON   42449365 43609316 44699286 45759173 46639037 46938870
            46378806 44968859 43848945 42539175 42299254 42449365

Mesoscale Discussions in Wisconsin, 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.