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Mesoscale Discussion 1219 |
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MESOSCALE DISCUSSION 1219
NWS STORM PREDICTION CENTER NORMAN OK
1243 PM CDT TUE JUN 25 2013
AREAS AFFECTED...E-CNTRL/NERN MO...A LARGE PART OF IL...PARTS OF FAR
ERN IA...PARTS OF FAR WRN INDIANA
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 251743Z - 252015Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...THUNDERSTORMS WILL LIKELY INCREASE IN COVERAGE AND
INTENSITY THROUGH THE AFTERNOON HOURS...AND MAY PRODUCE SVR WIND
GUSTS AND HAIL. THE AREA IS BEING MONITORED FOR POSSIBLE SVR TSTM
WATCH ISSUANCE.
DISCUSSION...EARLY AFTERNOON SFC MESOANALYSIS HIGHLIGHTS A COUPLE OF
SFC FEATURES THAT WILL POTENTIALLY SERVE AS FOCI FOR INITIAL
THUNDERSTORM DEVELOPMENT THIS AFTERNOON:
/1/ AN OUTFLOW BOUNDARY ARCING FROM NRN IL INTO E-CNTRL IA DEPOSITED
BY A CONVECTIVE CLUSTER WHICH MOVED ACROSS THAT GENERAL AREA EARLIER
TODAY...AND
/2/ A DIFFERENTIAL HEATING ZONE OVER THE FRINGES OF MULTI-LAYERED
CONVECTIVE CLOUD DEBRIS EXTENDING APPROXIMATELY W/E THROUGH CNTRL IL
AND NE/SW IN NERN/CNTRL MO. INITIAL CELL DEVELOPMENT HAS ALREADY
BEEN NOTED IN LOGAN COUNTY IL INVOF THE DIFFERENTIAL HEATING ZONE.
MODIFICATIONS TO THE ILX 12Z RAOB FOR SFC CONDITIONS S OF THE
OUTFLOW BOUNDARY SUGGEST MLCAPE HAS INCREASED TO AROUND 3000-3500
J/KG WITH VERY LITTLE MLCINH. CONTINUED DIABATIC SFC HEATING AMIDST
RICH LOW-LEVEL MOISTURE -- E.G. LOWEST 100-MB MEAN MIXING RATIO
AROUND 16.5 G/KG PER 12Z ILX RAOB -- BENEATH THE NEWD EXTENT OF AN
EML FEATURING 7-8-C/KM MID-LEVEL LAPSE RATES SHOULD YIELD A VERY
UNSTABLE AIR MASS THROUGH THE AFTERNOON.
PRESENT INDICATIONS ARE THAT CONVECTION WILL INCREASE IN
COVERAGE/INTENSITY THROUGH THE AFTERNOON...WHILE WEAK WAA
ACCOMPANYING A 20-30-KT LOW-LEVEL JET MAX PERSISTS. THE
AFOREMENTIONED DEGREE OF BUOYANCY SHOULD SUPPORT VIGOROUS
UPDRAFTS/DOWNDRAFTS...CAPABLE OF DMGG WINDS GUSTS AND SVR HAIL. WITH
25-35 KT OF EFFECTIVE BULK SHEAR -- HIGHEST N OF INTERSTATE 70 -- A
FEW ORGANIZED STORM STRUCTURES/SMALL CONVECTIVE CLUSTERS MAY ENSUE.
THERE IS SOME QUESTION REGARDING THE ANTICIPATED COVERAGE OF SVR
CONVECTION...HOWEVER...AS DEEP-LAYER FORCING FOR ASCENT SHOULD BE
LIMITED. REGARDLESS...THE AREA WILL BE MONITORED FOR THE POSSIBLE
ISSUANCE OF A SVR TSTM WATCH THROUGH THE AFTERNOON.
..COHEN/KERR.. 06/25/2013
ATTN...WFO...IND...LOT...ILX...LSX...DVN...SGF...EAX...
LAT...LON 41279080 41518886 41488749 40438722 39418782 38658890
38189047 38169215 39019262 41279080
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