226  
ACUS02 KWNS 260608  
SWODY2  
SPC AC 260607  
 
DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0107 AM CDT WED JUL 26 2017  
 
VALID 271200Z - 281200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MID  
MISSISSIPPI VALLEY EAST-NORTHEAST TO THE MID ATLANTIC REGION...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE  
SLIGHT RISK AREA...AND INCLUDING THE LOWER GREAT LAKES AND NEW  
ENGLAND...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS  
OF THE INTERMOUNTAIN REGION AND VICINITY...  
   
..SUMMARY
 
 
STRONG/LOCALLY SEVERE STORMS ARE FORECAST TO SPREAD ACROSS THE OHIO  
AND TENNESSEE VALLEYS, CENTRAL APPALACHIANS AND INTO THE MID  
ATLANTIC REGION AND VICINITY THURSDAY AFTERNOON AND EVENING.  
ISOLATED SEVERE RISK MAY ALSO EVOLVE ACROSS THE NORTHERN  
INTERMOUNTAIN REGION THURSDAY AFTERNOON/EVENING.  
   
..SYNOPSIS
 
 
AS A WEAK SHORT-WAVE TROUGH ADVANCES NORTHEAST INTO THE NORTHERN  
INTERMOUNTAIN REGION ON THE NORTHWEST FRINGE OF LARGE-SCALE RIDGING,  
AMPLIFICATION OF TROUGHING WILL OCCUR OVER THE EASTERN U.S. WHILE A  
SHORT-WAVE TROUGH DIGS SOUTHEAST ACROSS THE GREAT LAKES REGION.  
 
AT THE SURFACE, A WEAK COLD FRONT WILL ADVANCE ACROSS THE NORTHWEST  
STATES, WHILE A SECOND FRONT ADVANCES SOUTHEAST OUT OF CANADA AND  
INTO THE NORTHEAST U.S., AND SOUTHWARD ACROSS THE MIDWEST/OHIO  
VALLEY AREA. THESE BOUNDARIES WILL BE ASSOCIATED WITH THE TWO MAIN  
AREAS OF STRONGER CONVECTION THROUGH THE PERIOD.  
   
..MID MS/OH/TN VALLEYS EAST TO THE MID ATLANTIC REGION
 
 
MODELS REMAIN UNCERTAIN WITH RESPECT TO HANDLING OF LEAD UPPER  
SHORT-WAVE TROUGHING FORECAST TO CROSS THE OH AND TN VALLEYS/CENTRAL  
APPALACHIANS/MID ATLANTIC REGION DURING THE DAY THURSDAY, AHEAD OF  
THE MAIN TROUGH DIGGING SOUTHEAST ACROSS THE GREAT LAKES.  
DIFFERENCES ABOUND WITH RESPECT TO AMOUNT/INTENSITY/LOCATION OF  
CONVECTION ASSOCIATED WITH THIS LEAD TROUGH.  
 
AT THIS TIME, IT APPEARS THAT ISOLATED STORMS WILL SPREAD SOUTHEAST  
ACROSS THE GREAT LAKES REGION, AND ACROSS THE ST. LAWRENCE VALLEY  
INTO THE NORTHEAST U.S. DURING THE AFTERNOON. MODEST CAPE AND AMPLE  
SHEAR WILL LIKELY ALLOW A FEW STRONGER STORMS/STORM CLUSTERS TO  
EVOLVE, RESULTING IN LOCAL RISK FOR PRIMARILY DAMAGING WINDS.  
FARTHER SOUTHEAST INTO THE SLIGHT RISK AREA, MODELS CONTINUE TO  
INDICATE THAT DESTABILIZATION OF THE PRE-FRONTAL WARM SECTOR WILL  
SUPPORT AREAS OF STORM DEVELOPMENT -- AIDED BY ASCENT ASSOCIATED  
WITH THE AFOREMENTIONED LEAD UPPER TROUGH. SOME TREND IN THE MODELS  
IS EVIDENT TO INDICATE THAT GREATEST CONVECTIVE COVERAGE MAY NOW  
OCCUR WEST OF THE MOUNTAINS OVER THE OH/TN VALLEY AREA, WHERE AMPLE  
SHEAR FOR SOME STORM ORGANIZATION -- AND DAMAGING WIND RISK -- WOULD  
RESIDE. AS SUCH, WESTWARD EXPANSION OF THE SLIGHT RISK INTO THIS  
REGION IS BEING INCLUDED. OTHERWISE, LESS CERTAIN, ISOLATED SEVERE  
RISK IS STILL EXPECTED EAST OF THE MOUNTAINS INTO PARTS OF THE MID  
ATLANTIC AREA THUS WARRANTING CONTINUATION OF SLIGHT RISK AT THIS  
POINT. RISK MAY CONTINUE INTO THE OVERNIGHT HOURS, AS THE MAIN  
UPPER SYSTEM CONTINUES TO DIG SOUTHEAST.  
   
..NORTHERN INTERMOUNTAIN REGION TO THE CENTRAL HIGH PLAINS
 
 
MODEST, HIGH-BASED AFTERNOON CAPE DEVELOPMENT IS EXPECTED ACROSS  
PARTS OF THE INTERMOUNTAIN REGION THURSDAY, AS A WEAK SHORT-WAVE  
ADVANCES ANTICYCLONICALLY NORTHEAST AROUND THE NORTHWEST PORTION OF  
THE UPPER RIDGE. THIS WILL SUPPORT DEVELOPMENT OF ISOLATED TO  
SCATTERED STORMS -- ACROSS PARTS OF THE INTERMOUNTAIN REGION AS WELL  
AS INTO A LOW-LEVEL UPSLOPE FLOW REGIME OVER THE CENTRAL HIGH  
PLAINS. WITH MODERATE MID-LEVEL FLOW OVERSPREADING PARTS OF THE  
REGION IN CONJUNCTION WITH THE ADVANCING UPPER SYSTEM, A FEW  
STRONGER STORMS WILL LIKELY EMERGE FROM WITHIN THE BROADER AREA OF  
SHOWERS AND STORMS -- AND WILL BE CAPABLE OF PRODUCING EVAPORATIVELY  
AIDED DAMAGING WINDS. RISK SHOULD CONTINUE INTO THE EVENING, BEFORE  
STORMS BEGIN TO DIURNALLY DIMINISH IN COVERAGE/INTENSITY.  
 
..GOSS.. 07/26/2017  
 

 
 
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