842  
ACUS01 KWNS 300602  
SWODY1  
SPC AC 300601  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0101 AM CDT THU MAR 30 2017  
 
VALID 301200Z - 311200Z  
 
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN  
PARTS OF ILLINOIS AND INDIANA AND SOUTHWEST OHIO SOUTH ACROSS THE  
TENNESSEE VALLEY TO CENTRAL MISSISSIPPI...  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MID AND  
LOWER MISSISSIPPI VALLEY ACROSS THE OHIO VALLEY TO THE  
APPALACHIANS...AND SOUTH TO THE GULF COAST...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE  
SLIGHT RISK AREA...AND EXTENDING TO THE GEORGIA/SOUTH CAROLINA  
COASTAL AREA...  
   
..SUMMARY
 
 
SEVERE THUNDERSTORMS POTENTIALLY CAPABLE OF DAMAGING WINDS,  
TORNADOES, AND HAIL ARE FORECAST ON THURSDAY OVER PARTS OF THE  
MIDDLE AND LOWER MISSISSIPPI VALLEY INTO THE OHIO AND TENNESSEE  
VALLEYS.  
   
..SYNOPSIS
 
 
AN UPPER LOW CROSSING EASTERN KANSAS EARLY IN THE PERIOD IS FORECAST  
TO ACCELERATE EASTWARD ACROSS MISSOURI AND INTO THE MIDWEST THROUGH  
THE PERIOD -- AS A VIGOROUS SHORT-WAVE OVER THE PACIFIC NORTHWEST AT  
THE START OF THE PERIOD DIGS SOUTHEASTWARD WITH TIME, EVOLVING INTO  
A DEEPENING CLOSED LOW WITH TIME AND REACHING THE ARIZONA/UTAH  
BORDER REGION BY THE END OF THE PERIOD.  
 
AS THE EASTERN UPPER LOW IS KICKED EASTWARD BY THE DIGGING WESTERN  
SYSTEM, SHORT-WAVE TROUGHING -- WITHIN BROADER CYCLONIC FLOW  
SURROUNDING THE LOW -- WILL MOVE QUICKLY EASTWARD OUT OF THE  
SOUTHERN PLAINS AND ACROSS THE GULF OF MEXICO AND GULF COASTAL  
STATES. THIS WILL FACILITATE A RATHER RAPID EASTWARD ADVANCE OF A  
SURFACE COLD FRONT ACROSS THE SOUTHEAST QUARTER OF THE COUNTRY.  
THIS FRONT -- TRAILING SOUTHWARD FROM A PARENT LOW MOVING ACROSS THE  
OHIO VALLEY STATES THROUGH THE AFTERNOON AND EVENING -- SHOULD  
EXTEND FROM THE SOUTHERN APPALACHIANS TO THE FLORIDA PANHANDLE  
VICINITY BY 31/12Z.  
 
...THE MIDWEST SOUTH TO THE GULF COAST, AND THE MISSISSIPPI VALLEY  
EAST TO THE APPALACHIANS...  
A VERY COMPLEX WEATHER SCENARIO CONTINUES TO UNFOLD -- COMPLICATED  
LARGELY BY ONGOING SHOWERS AND LOCALLY STRONG TO SEVERE STORMS NOW  
AFFECTING THE MIDDLE AND LOWER MISSISSIPPI VALLEY AREA. MODELS  
SUGGEST THAT MUCH OF THIS CONVECTION WILL BE CONTAINED WITHIN TWO  
DISTINCT CLUSTERS AT THE START OF THE PERIOD -- ONE CROSSING THE MID  
MISSISSIPPI VALLEY INTO THE LOWER OHIO VALLEY AREA, AND A SECOND  
CROSSING SOUTHERN AND EASTERN MISSISSIPPI/EASTERN LOUISIANA. THE  
OHIO VALLEY CONVECTION IS FORECAST TO GRADUALLY WEAKEN THROUGH THE  
MORNING HOURS, WHILE THE SOUTHERN CLUSTER OF CONVECTION MAY PERSIST  
-- IN A LOCALLY SEVERE MANNER -- ACROSS THE CENTRAL GULF COASTAL  
REGION.  
 
THIS CONVECTION AND ASSOCIATED CLOUD COVER CONTINUES TO CAST  
UNCERTAINTY WITH RESPECT TO AREAS OF POTENTIALLY GREATER INSOLATION  
AND THUS DESTABILIZATION, BUT IT APPEARS THAT AT LEAST MODEST  
INSTABILITY WILL EVOLVE ALONG AND AHEAD OF THE ADVANCING COLD FRONT  
-- WHICH SHOULD EXTEND SOUTHWARD FROM A WESTERN ILLINOIS SURFACE LOW  
ROUGHLY ALONG THE MISSISSIPPI RIVER AROUND MIDDAY. WITH MIXED-LAYER  
CAPE VALUES LIKELY REACHING 500 TO 1500 J/KG BY EARLY AFTERNOON IN  
THE WAKE OF PRIOR CONVECTION, NEW STORM DEVELOPMENT SHOULD BEGIN.  
ORGANIZATION OF THE STORMS WILL BE AUGMENTED BY STRONG LOWER- AND  
MIDDLE-TROPOSPHERIC SOUTH-SOUTHWESTERLY FLOW, AND THOUGH TURNING  
WITH HEIGHT WILL REMAIN LIMITED IN MOST AREAS, SPEED SHEAR SUGGESTS  
BOTH ROTATING STORMS AND SMALL-SCALE BOWING SEGMENTS WILL EVOLVE  
WITH TIME. ALONG WITH POTENTIAL FOR HAIL, DAMAGING WINDS ARE  
EXPECTED, AND A FEW TORNADOES WILL BE POSSIBLE AS WELL --  
PARTICULARLY OVER THE LOWER OHIO VALLEY AREA WHERE A MORE  
SOUTHEASTERLY COMPONENT TO THE SURFACE FLOW SHOULD EXIST AHEAD OF  
THE LOW AND IN THE VICINITY OF THE WARM FRONT. CONVECTION MAY  
ORGANIZE INTO A BROKEN BAND, SPREADING EASTWARD ACROSS THE OHIO AND  
TENNESSEE VALLEYS AND CENTRAL GULF COASTAL STATES THROUGH THE  
AFTERNOON AND EVENING, ALONG WITH ATTENDANT SEVERE POTENTIAL.  
 
WITH AREAS OF MOST CONCENTRATED RISK DIFFICULT TO DISCERN, A BROAD  
ENH/LEVEL 3 RISK AREA IS BEING INCLUDED, WITH SLIGHT/LEVEL 2 RISK  
BEING EXPANDED EASTWARD AT THIS TIME -- BOTH ACROSS THE MID OHIO  
VALLEY ALONG THE MID-LEVEL LOW TRACK, AS WELL AS ACROSS THE SOUTHERN  
APPALACHIANS REGION AS A RAPIDLY ADVANCING SHORT-WAVE TROUGH FOSTERS  
INCREASING ASCENT THROUGH THE EVENING AND OVERNIGHT HOURS.  
 
..GOSS/COHEN.. 03/30/2017  
 

 
 
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