072  
ACUS01 KWNS 211253  
SWODY1  
SPC AC 211251  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0751 AM CDT SAT MAY 21 2022  
 
VALID 211300Z - 221200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE  
SOUTHERN PLAINS INTO THE LOWER OHIO VALLEY...LOWER GREAT LAKES AND  
NORTHEAST...  
   
..SUMMARY
 
 
SCATTERED SEVERE THUNDERSTORMS CAPABLE OF PRODUCING BOTH DAMAGING  
WINDS AND LARGE HAIL SHOULD DEVELOP THROUGH EVENING FROM PARTS OF  
THE SOUTHERN PLAINS INTO THE LOWER OHIO VALLEY, LOWER GREAT LAKES  
AND NORTHEAST. A TORNADO OR TWO MAY OCCUR AS WELL.  
   
..SYNOPSIS
 
 
THE LARGE-SCALE MID/UPPER-LEVEL PATTERN WILL CONTINUE TO BE  
DOMINATED BY A POSITIVELY TILTED TROUGH FROM NORTHEASTERN CANADA  
ACROSS THE NORTHERN PLAINS TO THE GREAT BASIN AND SOUTHERN CA.  
NUMEROUS SHORTWAVES WILL BE EMBEDDED IN THE ASSOCIATED CYCLONIC FLOW  
OVER THE NORTHERN PLAINS AND WESTERN CONUS, AND DOWNSTREAM SOUTHWEST  
FLOW ACROSS THE MIDWEST AND GREAT LAKES. HOWEVER, THE GREAT  
MAJORITY OF THESE, AND OF THE FASTEST FLOW ALOFT, WILL REMAIN BEHIND  
THE SURFACE FRONT DESCRIBED BELOW. EXCEPTIONS WILL INCLUDE MCVS  
PRODUCED BY ONGOING CONVECTION OVER THE OZARKS TO IN. A WEAK BUT  
STILL WELL-DEFINED SOUTHERN-STREAM SHORTWAVE TROUGH IS APPARENT IN  
MOISTURE-CHANNEL IMAGERY OVER CENTRAL/SOUTH-CENTRAL TX, AND SHOULD  
WEAKEN FURTHER AS IT MOVES NORTHEASTWARD TO PARTS OF EAST TX AND AR  
BY THIS EVENING.  
 
THE 11Z SURFACE ANALYSIS SHOWED A COLD FRONT FROM SOUTHWESTERN QC  
AND SOUTHEASTERN LOWER MI ACROSS WESTERN IN, SOUTH-CENTRAL MO,  
SOUTH-CENTRAL OK, TO BETWEEN MAF-HOB, NORTHWESTWARD INTO CENTRAL NM.  
THE FRONT SHOULD MOVE SLOWLY EASTWARD/SOUTHEASTWARD BY 00Z TO  
SOUTHERN PARTS OF QC/ON, NORTHERN IN, SOUTHERN IL, SOUTHERN MO,  
EXTREME SOUTHEASTERN OK, AND CENTRAL/SOUTHWEST TX. BY 12Z TOMORROW,  
THE FRONT SHOULD REACH PARTS OF OH, WESTERN KY/TN, NORTHERN LA, DEEP  
SOUTH TX, AND SOUTHERN COAHUILA. A WAVY WARM FRONT -- DRAWN  
INITIALLY ACROSS PORTIONS OF EASTERN NY/PA AND NORTHERN NJ -- WILL  
SHIFT NORTHEASTWARD OVER MOST OF NEW ENGLAND THROUGH TODAY.  
   
..SOUTHERN PLAINS TO NORTHEAST
 
 
WIDELY SCATTERED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP  
THROUGH THE PERIOD (INCLUDING ONGOING CLUSTERS FROM PARTS OF IN/OH  
TO NORTHWESTERN AR). WHILE SEVERE MAY OCCUR AT ALMOST ANY TIME FROM  
THE MOST INTENSE CELLS, THE GREATEST CONCENTRATION OF POTENTIAL  
SHOULD BE THIS AFTERNOON, UP AND DOWN THE OVER 2000-MILE-LONG SWATH.  
DAMAGING GUSTS AND LARGE HAIL SHOULD BE THE MOST COMMON SEVERE  
THREATS, THOUGH A TORNADO OR TWO MAY BE POSSIBLE (ESPECIALLY OVER  
PARTS OF WESTERN/NORTHERN MAINE AND THE OZARKS TO LOWER OHIO  
VALLEY).  
 
A LENGTHY CORRIDOR OF 60S F SURFACE DEW POINTS ALREADY IS OBSERVED  
FROM SOUTHEASTERN MO NORTHEASTWARD TO NORTHERN NY, WITH UPPER 60S  
AND LOW 70S OVER MUCH OF AR AND TX AHEAD OF THE FRONT. AREAS OF  
CLOUD COVER WILL SLOW DIURNAL HEATING OVER MUCH OF THE CORRIDOR EAST  
OF THE MISSISSIPPI RIVER; NONETHELESS, PRECONVECTIVE MLCAPE OF  
1000-2000 J/KG SHOULD DEVELOP. BUOYANCY WILL BE GREATER AMIDST  
LARGER BOUNDARY LAYER THETA-E AND STRONGER HEATING OVER AR AND TX,  
WITH 2000-3000 MLCAPE COMMON. EXCEPT FROM NEAR THE LOWER GREAT  
LAKES ACROSS NORTHERN NEW ENGLAND, AND PERHAPS PARTS OF NORTHERN AR,  
SUBSTANTIAL MID/UPPER WINDS AND THEIR CONTRIBUTION TO DEEP SHEAR  
WILL REMAIN WELL BEHIND THE FRONT. NEAR THE CANADIAN BORDER, SOME  
SUPERCELL POTENTIAL MAY PERSIST FROM SOUTHERN QC INTO NORTHERN AND  
NORTHWESTERN ME THIS AFTERNOON/EARLY EVENING BEFORE WEAKENING. [FOR  
SEVERE-WEATHER CONCERNS IN ADJOINING PARTS OF CANADA, REFER TO  
ENVIRONMENT CANADA PUBLIC WEATHER ALERTS FOR QUEBEC-SOUTH VIA  
WEATHER.GC/CA/WARNINGS.] CLUSTERS OF STRONG-SEVERE THUNDERSTORMS  
ALSO MAY CONCENTRATE ALONG OUTFLOW BOUNDARIES AHEAD OF THE FRONT,  
LEFT BY MORNING CONVECTION FROM PARTS OF THE LOWER OHIO VALLEY TO  
AR.  
 
ELSEWHERE, ISOLATED, LOCALIZED DAMAGING GUSTS OR MARGINAL HAIL MAY  
OCCUR THIS AFTERNOON FROM PULSE/MULTICELL CONVECTION, ACROSS A BROAD  
AREA OF THE SOUTH AHEAD OF THE COLD FRONT.  
 
..EDWARDS/KERR.. 05/21/2022  
 

 
 
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