885  
ACUS01 KWNS 281959  
SWODY1  
SPC AC 281958  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0258 PM CDT WED JUN 28 2017  
 
VALID 282000Z - 291200Z  
 
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR  
SOUTHEAST NE INTO NORTHERN IL/SOUTHERN WI...  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL  
HIGH PLAINS TO THE MIDDLE/UPPER MS VALLEY...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE  
NORTHERN ROCKIES TO THE GREAT LAKES...  
   
..SUMMARY
 
 
SEVERE THUNDERSTORMS WITH LARGE HAIL, WIND DAMAGE AND A FEW  
TORNADOES ARE EXPECTED ACROSS THE MIDDLE MISSOURI VALLEY  
NORTHEASTWARD INTO THE MIDDLE AND UPPER MISSISSIPPI VALLEY. OTHER  
MORE ISOLATED SEVERE STORMS MAY OCCUR IN THE CENTRAL PLAINS AND  
NORTHERN ROCKIES.  
   
..SEVERE-WEATHER THREAT AREAS
 
 
NO CHANGES WERE NEEDED WITH THE SEVERE-PROBABILITIES/CATEGORICAL  
SEVERE RISK AREAS, AS PREVIOUS FORECAST REASONING REMAINS VALID WITH  
THIS OUTLOOK ISSUANCE.  
   
..GENERAL THUNDERSTORM AREAS IN THE DAKOTAS AND EASTERN NY
 
 
BASED ON CONVECTIVE/LIGHTNING TRENDS IN EASTERN MT, THE GENERAL  
THUNDERSTORM LINE IN WESTERN ND WAS SHIFTED A LITTLE TO THE EAST TO  
INDICATE SOME POTENTIAL FOR THUNDERSTORMS TO REACH FAR WESTERN ND  
LATE THIS AFTERNOON TO EARLY EVENING. A LITTLE MORE OF CENTRAL SD  
WAS ADDED TO GENERAL THUNDERSTORM POTENTIAL FOR LATER TONIGHT.  
MEANWHILE, MUCH OF EASTERN SD/ND INTO FAR NORTHERN MN WAS REMOVED  
FROM THE GENERAL THUNDERSTORM AREA, GIVEN THE DECREASE IN  
THUNDERSTORM POTENTIAL WITHIN AN AREA OF MIDLEVEL SUBSIDENCE AND/OR  
WEAKER INSTABILITY.  
 
FARTHER EAST, CONVECTIVE TRENDS SUGGEST THUNDERSTORM POTENTIAL  
SHOULD CONTINUE TO SHIFT EAST/NORTHEAST AWAY FROM PORTIONS OF  
EASTERN NY.  
 
..PETERS.. 06/28/2017  
   
PREV DISCUSSION
 
/ISSUED 1136 AM CDT WED JUN 28 2017/  
   
..MIDDLE MO RIVER VALLEY TO MIDDLE/UPPER MS RIVER VALLEY
 
 
RELATED TO LAST NIGHT'S MCS, SCATTERED SHOWERS/THUNDERSTORMS AND  
RELATED PREVALENT CLOUD COVER CONTINUE TO PROGRESS EASTWARD ACROSS  
EASTERN PORTIONS OF MN/IA INTO WI/NORTHERN IL LATE THIS MORNING.  
THIS IS JUST AHEAD OF AN EASTWARD-MOVING SHORTWAVE TROUGH OVER MN,  
WITH A FEW OTHER CONVECTIVELY RELATED DISTURBANCES/MCVS NOTED  
FARTHER SOUTH, EMBEDDED WITHIN A BELT OF MODERATELY STRONG MID-LEVEL  
WESTERLIES. A SURFACE LOW ANALYZED AT 15Z NEAR THE MN/SD/ND BORDER  
VICINITY WILL CONTINUE TO SPREAD EASTWARD ACROSS CENTRAL MN TOWARD  
NORTHERN WI AND THE WESTERN UPPER PENINSULA OF MI THROUGH THIS  
EVENING, WHILE A COLD FRONT SPREADS SOUTHEASTWARD ACROSS MN/IA/WI.  
 
NEAR AND AHEAD OF THIS COLD FRONT, LOW-LEVEL MOISTENING AND GENERAL  
AIR MASS RECOVERY WILL STEADILY OCCUR THIS AFTERNOON IN THE WAKE OF  
THE LINGERING EARLY-DAY PRECIPITATION AND CLOUD COVER, PARTICULARLY  
GIVEN RELATIVELY STEEP MID-LEVEL LAPSE RATES AND AMPLE LOW-LEVEL  
MOISTURE SAMPLED IN SOURCE-REGION 12Z OBSERVED SOUNDINGS FROM OMAHA  
NE AND TOPEKA KS. INCREASINGLY PREVALENT MID/UPPER 60S F SURFACE  
DEWPOINTS WILL SUPPORT UPWARDS OF 2000-3000 J/KG MLCAPE PARTICULARLY  
FROM SOUTHEAST NE/NORTHERN KS INTO IA, WITH SOMEWHAT MORE MODEST  
(AND UNCERTAIN) DEGREE OF PRE-FRONTAL DESTABILIZATION FARTHER NORTH  
INTO WI/EASTERN MN OWING TO EARLY-DAY CLOUD COVER AND SOME  
REGENERATIVE PRECIPITATION THIS MORNING ACROSS NORTHERN IA.  
 
WHILE THE AFOREMENTIONED CLOUD COVER/PRECIPITATION LINGERING INTO  
MIDDAY STILL CASTS SOME UNCERTAINTY, IT SEEMS MOST LIKELY THAT  
SURFACE-BASED STORMS WILL REDEVELOP JUST AHEAD OF THE FRONT  
SEMI-FOCUSED ALONG OUTFLOW AND ZONES OF DIFFERENTIAL HEATING ACROSS  
SOUTHERN/EASTERN IA AND NEARBY FAR NORTHERN MO AND NORTHERN IL.  
PENDING ADEQUATE DESTABILIZATION, OTHER POTENTIALLY SEVERE  
DEVELOPMENT MAY OCCUR BY LATE AFTERNOON IN CLOSER PROXIMITY TO THE  
SURFACE LOW/FRONT FROM FAR EASTERN MN INTO WESTERN/CENTRAL WI.  
AROUND 40-45 KT OF EFFECTIVE SHEAR WILL SUPPORT SOME INITIAL  
SUPERCELLS CAPABLE OF LARGE HAIL, WITH A FEW TORNADOES POSSIBLE AS  
WELL GIVEN THE STRENGTH OF 2-3 KM AGL SOUTHWESTERLY WINDS AND  
RELATED 150-250 M2/S2 0-1 KM SRH (WITH PROSPECTIVE SURFACE-BASED  
CONVECTION). EASTWARD-MOVING CLUSTERS SHOULD EVOLVE BY EVENING WITH  
A RELATED INCREASE IN DAMAGING WIND POTENTIAL PARTICULARLY ACROSS  
SOUTHERN IA/NORTHERN MO INTO NORTHERN IL.  
   
..CO/WY FRONT RANGE TO NORTHERN KS/SOUTHERN NE
 
 
WITHIN A MODESTLY MOIST ENVIRONMENT, WIDELY SCATTERED THUNDERSTORMS  
SHOULD DEVELOP AND SPREAD EASTWARD ACROSS THE REGION BY LATE  
AFTERNOON INTO EVENING, INCLUDING SOME POTENTIAL FOR AT LEAST  
SMALL-SCALE MCS DEVELOPMENT THIS EVENING. MODEST BUOYANCY AND AMPLE  
VERTICAL SHEAR WILL SUPPORT THE POSSIBILITY OF SPORADIC LARGE HAIL  
AND LOCALLY DAMAGING WINDS INTO THIS EVENING.  
   
..NORTHERN ROCKIES
 
 
AHEAD OF AN AMPLIFYING SHORTWAVE TROUGH OVER THE NORTHERN  
INTERMOUNTAIN REGION, MODEST MOISTURE AND A STRENGTHENING BELT OF  
WEST-SOUTHWESTERLY MID-LEVEL WINDS SHOULD CONTRIBUTE TO THE  
POSSIBILITY OF ISOLATED STRONG TO SEVERE STORMS SPANNING PARTS OF  
WY/SOUTHERN MT AND EASTERN ID/NORTHERN UT.  
 

 
 
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