982  
ACUS02 KWNS 250525  
SWODY2  
SPC AC 250524  
 
DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1224 AM CDT THU JUL 25 2024  
 
VALID 261200Z - 271200Z  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS FAR  
SOUTHEAST MONTANA AND NORTHEAST WYOMING INTO WESTERN SOUTH  
DAKOTA...AND ACROSS FAR EASTERN NORTH DAKOTA INTO NORTHWEST  
MINNESOTA...  
   
..SUMMARY
 
 
ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS PARTS OF THE  
NORTHERN HIGH PLAINS AND FAR EASTERN NORTH DAKOTA INTO NORTHWEST  
MINNESOTA ON FRIDAY.  
   
..SYNOPSIS
 
 
A MORE PROGRESSIVE UPPER PATTERN IN EXPECTED ON FRIDAY AS AN UPPER  
TROUGH DEVELOPS WESTWARD ACROSS THE WESTERN U.S. THIS WILL SHUNT THE  
PLAINS UPPER RIDGE EAST, EXTENDING FROM THE GREAT LAKES, SOUTHWARD  
TO THE GULF COAST STATES. WHILE THE UPPER TROUGH ENVELOPS MUCH OF  
THE WESTERN U.S., AN UPPER ANTICYCLONE WILL REMAIN CENTERED OVER  
NORTHERN BAJA, AND EXTEND NORTHEAST INTO AZ/NM. AT THE SURFACE, A  
COLD FRONT WILL EXTEND SOUTHWARD ACROSS THE WESTERN DAKOTAS EARLY IN  
THE DAY. THE NORTHERN EXTENT OF THE FRONT WILL DEVELOP EAST TOWARD  
THE ND/MN BORDER BY 00Z, WHILE THE SD PORTION OF THE FRONT STALLS  
AND BECOMES DIFFUSE. SURFACE HIGH PRESSURE OVER THE GREAT LAKES WILL  
MAINTAIN A MOSTLY DRY AIRMASS FROM THE OHIO VALLEY INTO THE  
NORTHEAST IN THE WAKE OF A PRIOR COLD FRONTAL PASSAGE. MEANWHILE, A  
BAROCLINIC ZONE OVER THE UPPER MIDWEST WILL ALLOW FOR RICH BOUNDARY  
LAYER MOISTURE BENEATH THE EASTWARD-DEVELOP UPPER RIDGE.  
SOUTHWESTERLY LOW-LEVEL FLOW ACROSS NORTHWEST MEXICO INTO AZ WILL  
BRING MODEST BOUNDARY-LAYER MOISTURE INTO THE SOUTHERN AZ DESERTS AS  
WELL.  
   
..WY INTO WESTERN SD AND VICINITY
 
 
BOUNDARY-LAYER MOISTURE IS EXPECTED TO MODESTLY RETURN IN THE WAKE  
OF THE MORNING COLD FRONT AS THE BOUNDARY STALLS OVER  
WESTERN/CENTRAL SD. LOW-LEVEL FLOW IS EXPECTED TO BECOME  
EAST/SOUTHEASTERLY DURING THE AFTERNOON, ALLOWING FOR MODEST  
MOISTURE RETURN AND DESTABILIZATION IN THIS POST-FRONTAL UPSLOPE  
FLOW REGIME. FORECAST GUIDANCE SUGGESTS AT LEAST ISOLATED  
THUNDERSTORMS WILL DEVELOP AS LARGE-SCALE ASCENT INCREASES IN  
RESPONSE TO A SHORTWAVE IMPULSE MIGRATING THROUGH SOUTHWESTERLY  
FLOW, GENERATING MODEST HEIGHT FALLS ACROSS THE REGION. FORECAST  
SOUNDINGS INDICATE A DEEPLY MIXED BOUNDARY LAYER WITH INVERTED-V  
THERMODYNAMIC SUB-CLOUD PROFILES AMID 25 KT EFFECTIVE SHEAR  
MAGNITUDES. ISOLATED STRONG/SEVERE GUSTS MAY ACCOMPANY THUNDERSTORM  
ACTIVITY DURING THE EVENING, ESPECIALLY IF CLUSTERING/OUTFLOW  
CONSOLIDATION OCCURS.  
   
..EASTERN ND INTO MN
 
 
THUNDERSTORMS ARE EXPECTED TO DEVELOP AHEAD OF THE  
EASTWARD-ADVANCING COLD FRONT BY LATE FRIDAY AFTERNOON AS THE  
BOUNDARY IMPINGES ON RICHER BOUNDARY LAYER MOISTURE. INITIAL CAPPING  
SHOULD ERODE AS THE UPPER RIDGE SHIFTS EAST TOWARD THE GREAT LAKES,  
RESULTING IN FALLING HEIGHTS/COOLING ALOFT WHILE WARM ADVECTION  
CONTINUES IN THE LOW-LEVELS. EVEN IF WEAK CAPPING IS MAINTAINED,  
ELEVATED CONVECTION IS STILL EXPECTED. A NARROW CORRIDOR OF MLCAPE  
UP TO 2500 J/KG IS FORECAST AMID EFFECTIVE SHEAR MAGNITUDES AROUND  
35 KT, SUPPORTING ROBUST UPDRAFTS AND MARGINAL SUPERCELLS. ISOLATED  
HAIL WILL BE POSSIBLE IN ADDITION LOCALLY STRONG GUSTS.  
   
..AZ
 
 
MODEST BOUNDARY LAYER MOISTURE AND STEEP LAPSE RATES WILL SUPPORT  
AROUND 500-1000 J/KG MLCAPE. THUNDERSTORMS WILL ONCE AGAIN DEVELOP  
OVER HIGHER TERRAIN AND MOVE SOUTH DURING THE EVENING. MID AND  
UPPER-LEVEL FLOW WILL BE A BIT MORE NORTHERLY COMPARED TO THE PRIOR  
FEW DAYS AND FAIRLY WEAK (GENERALLY LESS THAN 15 KT). NEVERTHELESS,  
DEEP MIXING AND INVERTED-V THERMODYNAMIC PROFILES WILL SUPPORT  
SPORADIC STRONG GUSTS. GIVEN SOMEWHAT LESS FAVORABLE FLOW COMPARED  
TO RECENT DAYS, WILL HOLD OFF ON MARGINAL WIND PROBABILITIES AT THIS  
TIME.  
 
..LEITMAN.. 07/25/2024  
 

 
 
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