103  
ACUS03 KWNS 260731  
SWODY3  
SPC AC 260730  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0230 AM CDT WED JUL 26 2017  
 
VALID 281200Z - 291200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE  
MID ATLANTIC REGION AND THE CAROLINAS WEST ACROSS PARTS OF THE  
SOUTHEAST...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUND THE  
EASTERN/SOUTHEASTERN U.S. SLIGHT RISK...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF  
THE CENTRAL AND NORTHERN HIGH PLAINS AREA...  
   
..SUMMARY
 
 
STRONG/LOCALLY SEVERE STORMS ARE FORECAST ACROSS A LARGE PORTION OF  
THE EASTERN U.S. FRIDAY, FROM THE MIDDLE AND SOUTHERN ATLANTIC COAST  
WEST-SOUTHWEST ACROSS THE MID SOUTH AND SOUTHEAST. A COUPLE OF  
SEVERE STORMS WILL ALSO BE POSSIBLE OVER PARTS OF THE CENTRAL AND  
NORTHERN HIGH PLAINS VICINITY.  
   
..SYNOPSIS
 
 
WHILE LARGE-SCALE UPPER RIDGING LARGELY PREDOMINATES OVER THE  
WESTERN U.S. FRIDAY, SUBSTANTIAL AMPLIFICATION OF TROUGHING IS  
FORECAST OVER THE EASTERN U.S. WITH TIME. WHILE THE MODELS DIFFER  
FAIRLY SUBSTANTIALLY WITH RESPECT TO TIMING AND TRACK, A STRONG  
SHORT-WAVE TROUGH -- INITIALLY PROGGED OVER THE UPPER GREAT LAKES  
AREA -- WILL DIG SOUTHEAST TOWARD/INTO THE CENTRAL APPALACHIANS  
AREA.  
 
AT THE SURFACE, A FAIRLY STRONG COLD FRONT IS FORECAST TO SHIFT  
SOUTHEAST INTO -- AND ACROSS -- THE APPALACHIANS, WITH RELATIVELY  
SUBSTANTIAL CYCLOGENESIS EXPECTED TO OCCUR ALONG THE FRONT IN THE  
VICINITY OF THE MID ATLANTIC REGION. AGAIN, DETAILS WITH RESPECT TO  
LOCATION AND TIMING OF SURFACE SYSTEM PROGRESSION AND  
INTENSIFICATION DIFFER, BUT EXPECT A COLD FRONT TO EXTEND  
SOUTHWESTWARD ACROSS THE ATLANTIC AND GULF COAST STATES THROUGH  
LATTER STAGES OF THE PERIOD. WIDESPREAD -- AND LIKELY AT LEAST  
LOCALLY SEVERE -- CONVECTION IS EXPECTED TO PRECEDE FRONTAL PASSAGE.  
 
...MID SOUTH AND SOUTHEAST TO THE MIDDLE AND SOUTHERN ATLANTIC  
COAST...  
WHILE A LARGE DEGREE OF UNCERTAINTY EXISTS WITH RESPECT TO  
TIMING/LOCATION, EVOLUTION OF SEVERE CONVECTION IS EXPECTED ACROSS A  
RATHER BROAD AREA OF THE SOUTHERN AND EASTERN U.S. FRIDAY AHEAD OF  
THE ADVANCING COLD FRONT AND ASSOCIATED/DIGGING UPPER SYSTEM. AS  
ENHANCED/DIFFLUENT FLOW ALOFT SPREADS ACROSS THE AREA AHEAD OF THE  
UPPER SYSTEM, A FAVORABLE KINEMATIC ENVIRONMENT FOR  
ORGANIZED/FAST-MOVING BANDS OF STORMS WILL EXIST. THE MAIN  
QUESTIONS AT THIS TIME REVOLVE AROUND TIMING OF SYNOPTIC FEATURES,  
AND EVOLUTION OF PRIOR -- AND ONGOING -- CONVECTION, AND RELATED  
EFFECTS ON HEATING/DESTABILIZATION POTENTIAL. GIVEN THESE  
QUESTIONS, A BROAD 15%/SLIGHT RISK AREA IS BEING INCLUDED ACROSS  
WHAT APPEARS TO BE THE ZONE OF GREATEST RISK AT THIS POINT, WITH  
LATER ADJUSTMENTS TO AREA AND RISK LEVEL LIKELY TO BE REQUIRED.  
ALONG WITH RISK ACROSS PORTIONS OF THE MID ATLANTIC AREA AHEAD OF  
THE ANTICIPATED TRACK OF THE MAIN VORT MAX, THE BROAD ZONE OF  
ENHANCED/DIFFLUENT NORTHWEST FLOW ALOFT ACROSS A LARGE PORTION OF  
THE SOUTHEAST U.S. WOULD ALSO SUPPORT POTENTIAL FOR RATHER  
WIDESPREAD DAMAGING WIND RISK WITH MULTIPLE, UPSCALE-GROWING BANDS  
OF STORMS THROUGH THE AFTERNOON AND EVENING HOURS.  
   
..PORTIONS OF THE CENTRAL AND NORTHERN HIGH PLAINS
 
 
AS WEAK SHORT-WAVE TROUGHING CRESTS THE UPPER RIDGE AND BEGINS TO  
TURN EAST -- AND THEN SOUTHEAST -- AS IT SHIFTS ACROSS THE HIGH  
PLAINS, ISOLATED/AFTERNOON STORM DEVELOPMENT IS EXPECTED IN A  
MODESTLY DESTABILIZING HIGH PLAINS AIRMASS. AIDED BY UPSLOPE FLOW,  
STORMS MAY LOCALLY ORGANIZE AND MOVE SOUTHEAST OFF THE HIGH TERRAIN  
THROUGH THE EVENING, PERHAPS AS A SMALL MCS. LOCALLY DAMAGING WINDS  
WOULD LIKELY BE THE PRIMARY SEVERE RISK, ALONG WITH SOME HAIL  
POTENTIAL BEFORE STORMS DIMINISH INTO THE OVERNIGHT HOURS.  
 
..GOSS.. 07/26/2017  
 

 
 
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