664  
ACUS48 KWNS 240900  
SWOD48  
SPC AC 240858  
 
DAY 4-8 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0358 AM CDT THU JUL 24 2025  
 
VALID 271200Z - 011200Z  
   
..DISCUSSION
 
 
MODELS INDICATE SUBSTANTIVE AMPLIFICATION WITHIN AN INITIALLY ZONAL  
BELT OF WESTERLIES ACROSS THE NORTHERN MID-LATITUDE PACIFIC DURING  
THE COMING DAYS, WITH SEVERAL EMBEDDED CLOSED LOWS EVOLVING,  
INCLUDING ONE BY THE BEGINNING OF THE PERIOD ACROSS THE NORTHEASTERN  
PACIFIC, ON THE LEADING EDGE OF AN INCREASINGLY BLOCKED REGIME.  
DOWNSTREAM, AS ANOTHER SIGNIFICANT LOW, EMERGING FROM THE ARCTIC  
LATITUDES, TURNS ACROSS THE EASTERN NORTHWEST TERRITORIES INTO AND  
THROUGH HUDSON BAY, MID/UPPER RIDGING IS FORECAST TO BUILD THROUGH  
MUCH OF THE CANADIAN PRAIRIES. GRADUALLY, MODELS INDICATE THAT  
AMPLIFIED RIDGING WILL ENCOMPASS MUCH OF INTERIOR NORTH AMERICA,  
ACROSS AND EAST OF THE ROCKIES THROUGH THE MID TO LATTER PORTIONS OF  
NEXT WEEK, WHILE AMPLIFIED TROUGHING EVOLVES FURTHER DOWNSTREAM,  
ACROSS THE EASTERN CANADIAN PROVINCES, THE GREAT LAKES AND  
NORTHEAST.  
 
THE EVOLUTION OF THIS REGIME APPEARS LIKELY TO BE ACCOMPANIED BY A  
PLUME OF STEEPENING MID-LEVEL LAPSE RATES OVERSPREADING THE NORTHERN  
U.S. GREAT PLAINS AND ADJACENT PORTIONS OF SOUTHERN CANADA, TOWARD  
THE UPPER MIDWEST/GREAT LAKES, DURING THE EARLY TO MIDDLE PORTION OF  
NEXT WEEK, BEFORE BECOMING SUPPRESSED SOUTHWESTWARD. AIDED BY THE  
RETURN OF SEASONABLY HIGH BOUNDARY LAYER MOISTURE CONTENT TO AREAS  
NEAR AND NORTHEAST OF THE LOWER THROUGH MIDDLE MISSOURI VALLEY, IT  
APPEARS THAT THIS WILL CONTRIBUTE TO A BROAD AREA OF MODERATE TO  
LARGE POTENTIAL INSTABILITY.  
 
THIS ENVIRONMENT MAY BECOME CONDITIONALLY SUPPORTIVE OF THE  
EVOLUTION OF LONGER-LIVED ORGANIZED THUNDERSTORM CLUSTERS, WITH  
POTENTIAL TO PRODUCE SWATHS OF DAMAGING WIND GUSTS ACROSS PARTS OF  
THE NORTHERN GREAT PLAINS, UPPER MIDWEST AND GREAT LAKES INTO THE  
OHIO VALLEY AND PERHAPS PARTS OF THE NORTHEAST. HOWEVER, PRIOR TO  
MORE SUBSTANTIVE MID/UPPER TROUGH AMPLIFICATION, AND THE SOUTHWARD  
ADVANCEMENT OF A COLD FRONT INTO MUCH OF THE NORTHEASTERN U.S. BY  
THE MIDDLE OF NEXT WEEK, THE EVOLUTION OF ANY SUCH CLUSTER, SOUTH OF  
THE INTERNATIONAL BORDER, WILL LIKELY LARGELY DEPEND ON SUBTLE SHORT  
WAVE PERTURBATIONS PROGRESSING THROUGH THE LARGER SCALE RIDGING.  
GIVEN THE LOW PREDICTABILITY OF THESE FEATURES AT THIS EXTENDED  
RANGE, AND THE UNCERTAIN IMPACTS OF THEIR ASSOCIATED CONVECTION AND  
OUTFLOW ON SUBSEQUENT DESTABILIZATION, SEVERE PROBABILITIES REMAIN  
LOW DUE TO THE UNCERTAINTIES.  
 
..KERR.. 07/24/2025  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab SPC Page Main Text Page