120  
ACUS03 KWNS 220647  
SWODY3  
SPC AC 220646  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0146 AM CDT THU AUG 22 2019  
 
VALID 241200Z - 251200Z  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE  
NORTHERN PLAINS...  
   
..SUMMARY
 
 
AT LEAST ISOLATED SEVERE STORMS ARE POSSIBLE OVER PARTS OF THE  
NORTHERN PLAINS SATURDAY.  
   
..SYNOPSIS
 
 
STRONG CYCLONIC FLOW ALOFT WILL DEVELOP SOUTHEASTWARD INTO THE  
NORTHERN ROCKIES, PROVIDING INCREASED DEEP-LAYER SHEAR AND COOLING  
ALOFT TO THE NORTHERN HIGH PLAINS. A WEAK SHORTWAVE TROUGH WILL  
PRECEDE THIS LARGER-SCALE WAVE, AIDING LIFT OVER THE DAKOTAS AND MN  
DURING THE DAY.  
 
AT THE SURFACE, LOW PRESSURE WILL DEEPEN OVER THE NORTHERN HIGH  
PLAINS, ENHANCING SOUTHERLY SURFACE WINDS AND MAINTAINING A PLUME OF  
60S F DEWPOINTS FROM KS TO SOUTHERN MANITOBA. CONVERGENCE ALONG A  
COLD FRONT WILL INCREASE OVERNIGHT AND INTO SUNDAY MORNING FROM  
EASTERN MT TOWARD THE BLACK HILLS, PROVIDING LIFT.  
 
ELSEWHERE, A MOIST AND UNSTABLE AIR MASS WILL REMAIN OVER THE  
SOUTHERN PLAINS AND LOWER MS VALLEY, WITH VARIOUS AREAS OF STORMS  
AND OUTFLOW BOUNDARIES THROUGHOUT THE PERIOD. ANY POTENTIAL MARGINAL  
THREAT AREA HERE FOR WIND GUSTS IS CURRENTLY UNPREDICTABLE.  
   
..NORTHERN PLAINS
 
 
STORMS ARE LIKELY TO BE ONGOING ACROSS THE CENTRAL DAKOTAS, AND  
POSSIBLY INTO NORTH-CENTRAL NE SATURDAY MORNING, NEAR THE EASTERN  
INSTABILITY GRADIENT WHERE SOUTHWESTERLY 850 MB WINDS OF 30-40 KT  
WILL PROVIDE LIFT VIA WARM ADVECTION. MARGINAL HAIL CANNOT BE RULED  
OUT EARLY.  
 
LATER IN THE DAY, HEATING WILL REMOVE CIN OVER THE CENTRAL AND  
WESTERN DAKOTAS, AND REDEVELOPMENT IS POSSIBLE NEAR THE TAIL END OF  
THE DEPARTING LEAD WAVE OVER ND. VEERING WINDS WITH HEIGHT WILL  
FAVOR A SUPERCELL OR TWO, WITH SEVERE THREAT DEPENDENT ON HOW MUCH  
INSTABILITY CAN DEVELOP NEAR AN AXIS OF 200-300 M2/S2 EFFECTIVE SRH.  
ISOLATED CELLS ARE ALSO POSSIBLE AT PEAK HEATING OVER WESTERN SD.  
 
OVERNIGHT, LARGE-SCALE LIFT WILL INCREASE FROM MT INTO THE WESTERN  
DAKOTAS. STEEP LAPSE RATES ALOFT AND STRENGTHENING DEEP-LAYER SHEAR  
WILL CONDITIONALLY FAVOR SEVERE STORMS, HOWEVER, IT IS UNCLEAR HOW  
MUCH MOISTURE AND INSTABILITY WILL EXIST OVERNIGHT THAT FAR WEST.  
PARTS OF THE AREA MAY REQUIRE A CATEGORICAL UPGRADE IN FUTURE  
OUTLOOKS SHOULD INSTABILITY INCREASE.  
 
..JEWELL.. 08/22/2019  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab SPC Page Main Text Page