003  
ACUS03 KWNS 250826  
SWODY3  
SPC AC 250825  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0225 AM CST THU FEB 25 2021  
 
VALID 271200Z - 281200Z  
   
..NO SEVERE THUNDERSTORM AREAS FORECAST
 
 
   
..SUMMARY
 
 
THE RISK OF SEVERE THUNDERSTORMS CURRENTLY APPEARS NEGLIGIBLE ACROSS  
THE U.S. FOR SATURDAY THROUGH SATURDAY NIGHT.  
   
..DISCUSSION
 
 
SUPPRESSION OF AN INITIALLY PROMINENT BLOCKING HIGH AND AMPLIFIED  
MID-LEVEL RIDGING ACROSS THE EASTERN PACIFIC APPEARS LIKELY TO  
CONTINUE DURING THIS PERIOD, AS A SIGNIFICANT SHORT WAVE TROUGH  
PROGRESSES AROUND ITS NORTHERN PERIPHERY, ACROSS THE NORTHEASTERN  
PACIFIC. A MORE PRONOUNCED SPLIT IN THE DOWNSTREAM FLOW MAY DEVELOP  
INLAND OF THE PACIFIC COAST, AS SHORT WAVE RIDGING SHIFTS ACROSS  
BRITISH COLUMBIA AND ADJACENT PORTIONS OF THE U.S. PACIFIC  
NORTHWEST. BY LATE SATURDAY NIGHT, THE LEADING EDGE OF THIS REGIME  
MAY BEGIN TO TRANSLATE TO THE NORTH OF A VIGOROUS SHORT WAVE IMPULSE  
SHARPLY DIGGING ACROSS THE GREAT BASIN INTO THE LOWER COLORADO RIVER  
VICINITY OF THE SOUTHWEST.  
 
ACROSS AND EAST-NORTHEAST OF THE ROCKIES, MID-LEVEL FLOW IS FORECAST  
TO TREND INCREASINGLY CONFLUENT, BETWEEN MORE PROMINENT SUBTROPICAL  
RIDGING ACROSS THE GULF OF MEXICO INTO THE SOUTHEAST AND A VIGOROUS  
SHORT WAVE IMPULSE PIVOTING SOUTHEASTWARD OUT OF THE ARCTIC. AS  
THIS PERTURBATION DIGS ACROSS SASKATCHEWAN AND MANITOBA, AN  
INCREASINGLY SHEARED SHORT WAVE IMPULSE IS FORECAST TO ACCELERATE  
NORTHEAST OF THE WYOMING/COLORADO ROCKIES TOWARD THE UPPER MIDWEST,  
WHILE A MORE AMPLIFIED DOWNSTREAM IMPULSE ACCELERATES EAST OF THE  
GREAT LAKES INTO THE CANADIAN MARITIMES. EACH OF THESE LATTER  
FEATURES MAY BE ACCOMPANIED BY DEVELOPING SURFACE CYCLONES, WHILE  
COLD SURFACE RIDGING BUILDS BENEATH THE CONFLUENT FLOW ACROSS THE  
GREAT PLAINS, AS FAR SOUTH AS THE TEXAS/OKLAHOMA PANHANDLE REGION BY  
12Z SUNDAY.  
 
THE NET RESULT OF THESE DEVELOPMENTS IN LOWER LEVELS IS EXPECTED TO  
BE THE EVOLUTION AND/OR REINFORCEMENT OF A FRONTAL ZONE NEAR THE  
NORTHERN PERIPHERY OF THE MID-LEVEL SUBTROPICAL RIDGING, FROM NEAR  
OR SOUTH OF THE TEXAS BIG BEND INTO THE MID ATLANTIC COAST VICINITY.  
SOUTH/SOUTHWESTERLY LOW-LEVEL RETURN FLOW, OFF A STILL MODIFYING  
BOUNDARY LAYER OVER THE GULF OF MEXICO, WILL CONTRIBUTE TO  
MOISTENING AND DESTABILIZATION ALONG AND NORTH OF THIS FRONT. THIS  
WILL BECOME THE FOCUS FOR AREAS OF SCATTERED THUNDERSTORM  
DEVELOPMENT SATURDAY THROUGH SATURDAY NIGHT, WITH MODELS INDICATING  
THAT WARM LAYERS ALOFT AND SUBSIDENCE WILL SUPPRESS CONVECTIVE  
DEVELOPMENT TO THE SOUTH OF THE FRONT.  
 
MODELS DO INDICATE THAT SOUTHWESTERLY FLOW AROUND THE 850 MB LEVEL  
MAY STRENGTHEN TO 40-50+ KT ACROSS THE ARKANSAS/KENTUCKY/TENNESSEE  
VICINITY LATE SATURDAY AFTERNOON AND EVENING. IT MIGHT NOT BE OUT  
OF THE QUESTION THAT THIS COULD CONTRIBUTE TO A RISK FOR ORGANIZING  
STORMS WITH THE POTENTIAL TO PRODUCING DAMAGING SURFACE GUSTS.  
HOWEVER, MUCH MAY DEPEND ON HOW CLOSE CONVECTION FORMS TO THE  
SURFACE FRONTAL POSITION (AND THE DEPTH OF THE NEAR-SURFACE STABLE  
LAYER BELOW THE CONVECTION). WITH THIS UNCERTAIN, AND MODEL OUTPUT  
STILL INDICATING ONLY GENERALLY WEAK DESTABILIZATION, SEVERE  
PROBABILITIES APPEAR LESS THAN 5 PERCENT AT THE PRESENT TIME.  
 
..KERR.. 02/25/2021  
 

 
 
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