030  
ACUS48 KWNS 200945  
SWOD48  
SPC AC 200943  
 
DAY 4-8 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0343 AM CST MON JAN 20 2020  
 
VALID 231200Z - 281200Z  
   
..DISCUSSION
 
 
MEDIUM-RANGE MODEL SOLUTIONS HAVE COME INTO BETTER AGREEMENT  
RECENTLY, WITH THE GFS, ECMWF, AND NAM VERY SIMILAR WITH RESPECT TO  
THE BROAD PATTERN OVER THE U.S. AT 84 HOURS.  
 
BEYOND DAY 3 AND INTO THE MEDIUM RANGE, THE GFS AND ECMWF DO BEGIN  
TO MODERATELY DIVERGE, WITH RESPECT TO PROGRESSION AND EVOLUTION OF  
CENTRAL U.S. UPPER TROUGHING, AS IT SHIFTS EASTWARD ACROSS THE MID  
MISSISSIPPI AND INTO THE TENNESSEE/OHIO VALLEYS AND EVOLVES INTO A  
CLOSED LOW THROUGH THE END OF DAY 4 (THURSDAY) AND INTO DAY 5  
(FRIDAY).  
 
BY SUNSET FRIDAY, THE CLOSED LOW IS DEPICTED BY THE GFS TO LIE NEAR  
THE ILLINOIS/INDIANA BORDER, WHILE THE ECMWF CENTERS THE LOW OVER  
NORTHERN ALABAMA. AS A RESULT, THE GFS PLACES THE MAIN/ASSOCIATED  
SURFACE LOW MUCH FARTHER NORTH (ILLINOIS/INDIANA) THAN THE EURO  
(WHICH DEPICTS THE LOW OVER THE SAVANNAH RIVER AFTER SUNSET FRIDAY).  
 
IN EITHER CASE HOWEVER, AN INCOMPLETELY MODIFIED GULF BOUNDARY LAYER  
IS EXPECTED, DUE TO RECENT POLAR SURFACE HIGH INTRUSION. THIS --  
COMBINED WITH WEAK SURFACE REFLECTION OF THE UPPER SYSTEM AND THUS  
WEAK NORTHWARD THETA-E RETURN -- SUGGEST THAT ANY SEVERE-WEATHER  
RISK WOULD BE LOW, ACROSS THE REGION. AS SUCH, NO RISK AREAS APPEAR  
TO BE NECESSARY AT THIS TIME.  
 
WITH A COLD FRONT ASSOCIATED WITH THIS SYSTEM PROGGED NEAR THE  
ATLANTIC COAST AT THE START OF DAY 6, WHILE HIGH PRESSURE SETTLES  
ACROSS THE CENTRAL AND EASTERN U.S. IN ITS WAKE, CONVECTIVE  
POTENTIAL WILL DIMINISH OVER THE COUNTRY. WHILE A PACIFIC TROUGH IS  
THEN EXPECTED TO MOVE ONSHORE OVER THE WEST DAY 7, AND ACROSS THE  
ROCKIES DAY 8, DIFFERENCES AMONGST THE MODELS WITH THE EVOLUTION OF  
THIS FEATURE PRECLUDE ANY ASSESSMENT OF CONVECTIVE POTENTIAL AT THIS  
TIME.  
 
..GOSS.. 01/20/2020  
 
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