DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1128 AM CDT MON SEP 01 2014 VALID 011630Z - 021200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF NORTHERN OKLAHOMA AND SOUTHERN KANSAS TO THE MID-MISSISSIPPI VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF MICHIGAN... ...SUMMARY... ISOLATED TO SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED FROM PORTIONS OF NORTHERN OKLAHOMA AND SOUTHERN KANSAS TO THE MID-MISSISSIPPI VALLEY LATER TODAY INTO TONIGHT...AND ACROSS PORTIONS OF MICHIGAN THIS AFTERNOON. ...SYNOPSIS... WATER VAPOR LOOPS INDICATE BROADLY CYCLONIC FLOW EXTENDING FROM CANADA INTO THE N-CNTRL CONUS...WITH ONE EMBEDDED SHORTWAVE TROUGH LIFTING NEWD ACROSS PARTS OF THE WRN GREAT LAKES...AND AN UPSTREAM SPEED MAX EMERGING OVER THE CNTRL HIGH PLAINS. THESE FEATURES WILL CONTINUE TO ADVANCE THROUGH THE BROADER CYCLONIC FLOW...SERVING TO MAINTAIN A BELT OF MODERATE TO STRONG MID-LEVEL WLYS/SWLYS FROM THE CNTRL PLAINS TO THE GREAT LAKES. AN EXTENSIVE SFC FRONT LIES FROM WRN LAKE SUPERIOR SWWD TO THE TX PANHANDLE. THIS BOUNDARY WILL ADVANCE EWD ACROSS PARTS OF THE MIDWEST AND GREAT LAKES...WHILE TRAILING SWWD INTO THE SRN PLAINS AS A STATIONARY FRONT. ...PORTIONS OF THE SOUTHERN PLAINS NORTHEASTWARD TO THE GREAT LAKES REGION THIS AFTERNOON INTO TONIGHT... EXTENSIVE CONVECTIVE DEBRIS COVERS THE WARM/MOIST SIDE OF THE BOUNDARY AT PRESENT. REGARDLESS...SFC DEWPOINTS IN THE UPPER 60S/LOWER 70S EXTEND POLEWARD TO AN OUTFLOW BOUNDARY/PRE-FRONTAL TROUGH ANALYZED FROM NRN OK TO THE MID-MS VALLEY TO LAKE MI. THIS WILL SUPPORT CORRIDORS OF AT LEAST MODEST CONDITIONAL INSTABILITY TO ENHANCE THE POTENTIAL FOR LATER GENERATIONS OF CONVECTIVE DEVELOPMENT. THE SEGMENT OF THE OUTFLOW BOUNDARY/PRE-FRONTAL TROUGH FROM THE SRN PLAINS TO THE OZARKS TROUGH LIES BENEATH AN EML PLUME SAMPLED BY THE 12Z OUN SOUNDING...WHICH FEATURES A PROMINENT WARM LAYER BENEATH H7-H5 LAPSE RATES AROUND 8.3 C/KM. AS POCKETS OF INSOLATION MATERIALIZE IN THE WAKE OF ONGOING CLOUDS/PRECIPITATION...MLCAPE VALUES WILL LIKELY INCREASE TO 2000-3000 J/KG GIVEN THE AMPLE BOUNDARY MOISTURE DEWPOINTS AND STEEP MID-LEVEL LAPSE RATES. DESPITE QUASI-NEUTRAL MID-LEVEL HEIGHT TENDENCIES...CONVERGENCE ALONG THE AFOREMENTIONED SFC BOUNDARIES SHOULD BE SUFFICIENT FOR ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT BY LATE AFTERNOON FROM NERN OK AND SERN KS INTO SRN MO...WITH ACTIVITY INCREASING IN COVERAGE INTO THE EVENING HOURS WITH A NOCTURNALLY INCREASING LLJ. THE PRESENCE OF AROUND 30-40 KT OF EFFECTIVE BULK SHEAR WILL BE SUFFICIENT FOR INITIALLY ROTATING STORMS...WITH ACTIVITY LIKELY CONGEALING INTO CONVECTIVE CLUSTERS THAT WILL SPREAD EWD/ESEWD INTO THE OVERNIGHT HOURS. DMGG WIND GUSTS...LARGE HAIL -- SOME POSSIBLY SIGNIFICANT DURING INCIPIENT SUPERCELL PHASES -- AND A TORNADO OR TWO WILL BE POSSIBLE. MEANWHILE...STRONGER DEEP-LAYER ASCENT RELATED TO THE AFOREMENTIONED SHORTWAVE TROUGH WILL REMAIN CONFINED TO PORTIONS OF MI DURING THE NEXT SEVERAL HOURS. DCVA PRECEDING THE TROUGH IS EMERGING OVER AREAS OF A DIURNALLY HEATED...MOIST BOUNDARY LAYER TO SUPPORT RECENT THUNDERSTORM DEVELOPMENT OVER WRN LOWER MI. STRONG MID-LEVEL FLOW ATTENDANT TO THE TROUGH WILL HAVE THE POTENTIAL TO SUPPORT ORGANIZED MULTICELL CLUSTERS AND PERHAPS A SUPERCELL OR TWO WITH DMGG WIND GUSTS AND POSSIBLY A TORNADO. ELSEWHERE...THE AFOREMENTIONED SHORTWAVE TROUGH WILL BECOME INCREASINGLY REMOVED FROM THE PRE-FRONTAL REGIME BETWEEN THE TWO SLIGHT-RISK AREAS...WHERE WIDESPREAD CLOUDS ARE STUNTING DESTABILIZATION AMIDST POOR MID-LEVEL LAPSE RATES. THESE FACTORS WILL MARGINALIZE THE SVR-TSTM POTENTIAL IN THESE AREAS. ...EASTERN WYOMING / NORTHERN NEBRASKA / SOUTHERN SOUTH DAKOTA... ASCENT IN THE EXIT REGION OF THE AFOREMENTIONED MID-LEVEL SPEED MAX WILL ENCOURAGE TSTM DEVELOPMENT THIS AFTERNOON AS STEEP LOW/MID-LEVEL LAPSE RATES BECOME ESTABLISHED. MID-LEVEL FLOW WILL BE SUFFICIENTLY STRONG FOR A FEW MULTICELL CLUSTERS WITH SPORADIC SVR WIND GUSTS POSSIBLE. HOWEVER...THE LACK OF MORE ROBUST BOUNDARY-LAYER MOISTURE/BUOYANCY SHOULD PREVENT A MORE SUBSTANTIAL SVR RISK FROM EVOLVING.
Posted on: Mon, 01 Sep 2014 16:38:02 +0000
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