AREAS AFFECTED...PORTIONS OF SRN IA...WRN IL...NRN - TopicsExpress



          

AREAS AFFECTED...PORTIONS OF SRN IA...WRN IL...NRN MO...NERN KS...FAR SERN NEB CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 281812Z - 282045Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...THE AREA IS BEING MONITORED FOR MARGINAL SVR-TSTM POTENTIAL THROUGH THE AFTERNOON. WHILE CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED...WW ISSUANCE IS CURRENTLY UNLIKELY. DISCUSSION...SFC MESOANALYSIS INDICATES A STATIONARY BOUNDARY BISECTING IA FROM NW TO SE THAT EXTENDS FARTHER SE TO THE LOWER OHIO VALLEY. BROAD...MODEST ISENTROPIC ASCENT IS MAINTAINING CLOUDS...SHOWERS...AND THUNDERSTORMS ON EITHER SIDE OF THIS BOUNDARY. THIS HAS GIVEN RISE TO A WAVY DIFFERENTIAL HEATING BOUNDARY ANALYZED ACROSS NRN MO INTO NERN KS. SFC WIND FIELDS SUGGEST THAT CONVERGENCE ALONG EITHER OF THESE BOUNDARIES IS WEAK. HOWEVER...DIURNALLY DEEPENING PBL CIRCULATIONS COUPLED WITH STRENGTHENING BAROCLINICITY INVOF THE DIFFERENTIAL HEATING BOUNDARY WILL LIKELY FOSTER AN INCREASE IN CONVECTIVE COVERAGE AND INTENSITY DURING THE NEXT FEW HOURS...AS LOW-LEVEL WAA PERSISTS -- ESPECIALLY NEAR/ON THE COOLER SIDE OF THE DIFFERENTIAL HEATING BOUNDARY. STRONG HEATING OF RICH BOUNDARY-LAYER MOISTURE CONTINUES ON THE WARM SIDE OF THIS BOUNDARY...SUPPORTING 1000-2000 J/KG OF MLCAPE. HOWEVER...VWP DATA SUGGEST THAT ANY SUBSTANTIVE DEEP-LAYER SHEAR CAPABLE OF SUPPORTING MORE ORGANIZED/SUSTAINED STORMS EXISTS ON THE COLD SIDE OF THIS BOUNDARY WHERE INSTABILITY IS MORE MARGINAL. NEVERTHELESS...THE OVERLAP OF BUOYANCY/VERTICAL SHEAR MAY BE SUFFICIENT ACROSS THE MCD AREA TO SUPPORT A FEW MULTICELL CLUSTERS WITH LOCALLY DMGG WIND GUSTS AND PERHAPS MARGINALLY SVR HAIL. A BRIEF/TRANSIENT SUPERCELL OR TWO MAY ALSO OCCUR WHERE SFC WINDS ARE MORE BACKED BENEATH 25-30-KT MID-LEVEL WSWLYS SAMPLED BY THE DMX/DVN VWPS N OF THE DIFFERENTIAL HEATING BOUNDARY. SUCH ACTIVITY COULD PRODUCE A WEAK TORNADO. HOWEVER...WITHOUT GREATER COVERAGE OF FAVORABLE JUXTAPOSITION OF STRONGER BUOYANCY/SHEAR FOR SVR THUNDERSTORMS...THE OVERALL SVR POTENTIAL SHOULD REMAIN LIMITED. ..COHEN/MEAD.. 08/28/2014 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LSX...DVN...DMX...EAX...OAX...TOP... LAT...LON 41679144 41599047 40569061 39989141 39579266 39029586 39219631 40069564 41109370 41679144
Posted on: Thu, 28 Aug 2014 18:12:52 +0000

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