465  
ACUS01 KWNS 251956  
SWODY1  
SPC AC 251955  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0255 PM CDT THU SEP 25 2025  
 
VALID 252000Z - 261200Z  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF  
THE NORTHEAST...MID ATLANTIC AND SOUTHWEST...  
   
..SUMMARY
 
 
SCATTERED THUNDERSTORMS ARE EXPECTED FROM THE SOUTHEAST TO SOUTHERN  
NEW ENGLAND TODAY. ISOLATED DAMAGING WINDS AND PERHAPS A TORNADO OR  
TWO WILL BE POSSIBLE WITH SOME OF THIS CONVECTION. ADDITIONAL  
THUNDERSTORMS POSING A RISK FOR MARGINALLY SEVERE HAIL AND WIND MAY  
OCCUR ACROSS PARTS OF THE SOUTHWEST.  
   
..20Z UPDATE
 
 
NO MAJOR CHANGES WILL BE MADE TO THE VALID OUTLOOK. SCATTERED,  
OCCASIONALLY SEVERE, STORMS ARE LIKELY AHEAD OF THE COLD FRONT INTO  
EARLY THIS EVENING ACROSS PARTS OF THE MID ATLANTIC AND SOUTHERN NEW  
ENGLAND. VERY MOIST SURFACE CONDITIONS (LOW 70S F SURFACE DEWPOINTS)  
AND INTERMITTENT WARMING AMIDST CLOUD COVER IS SUPPORTING WEAK  
INSTABILITY. A LOW-TOPPED BAND OF SHOWERS AND STORMS ALONG THE COLD  
FRONT IN EASTERN PA AND WESTERN NY SHOULD CONTINUE EASTWARD INTO  
THIS EVENING. A FEW STRONGER UPDRAFTS WITH TRANSIENT ROTATION REMAIN  
POSSIBLE. ISOLATED DAMAGING GUSTS AND A BRIEF TORNADO ARE POSSIBLE.  
SEE THE PREVIOUS DISCUSSION AND MCD#2128 FOR ADDITIONAL INFORMATION.  
 
   
..SOUTHWEST
 
 
A FEW SEVERE STORMS ARE ALSO POSSIBLE OVER PARTS OF THE SOUTHWEST  
THROUGH THIS EVENING. INITIALLY TIED TO THE HIGHER TERRAIN, STORM  
COVERAGE SHOULD GRADUALLY INCREASE FROM SOUTHERN AZ INTO NV AND  
SOUTHWEST UT THIS AFTERNOON. MODEST BUOYANCY (MUCAPE 500-1000 J/KG)  
AND 20-30 KT OF VERTICAL SHEAR BENEATH THE UPPER LOW SHOULD SUPPORT  
A FEW MORE PERSISTENT STORMS WITH AN ISOLATED HAIL/WIND THREAT. A  
FEW STRONGER STORMS MAY LINGER THIS EVENING AS MODEST MID-LEVEL  
DESTABILIZATION CONTINUES BENEATH THE UPPER LOW. SEE MCD#2129 FOR  
UPDATED SORT-TERM FORECAST INFORMATION.  
 
..LYONS.. 09/25/2025  
   
PREV DISCUSSION
 
/ISSUED 1119 AM CDT THU SEP 25 2025/  
   
..SOUTHEAST STATES INTO SOUTHERN NEW YORK/NEW ENGLAND
 
 
RECENT SATELLITE IMAGERY REVEALS A LARGE POSITIVELY TILTED UPPER  
TROUGH THAT EXTENDS FROM THE SOUTHERN PLAINS THROUGH THE UPPER GREAT  
LAKES. RECENT SURFACE ANALYSIS PLACES A LARGE AREA OF LOWER PRESSURE  
FROM THE NORTH-CENTRAL GULF INTO EASTERN ONTARIO/SOUTHERN QUEBEC,  
JUST AHEAD OF THE UPPER TROUGHING. TWO SURFACE LOWS WERE ANALYZED AT  
14Z, ONE OVER WESTERN TN AND ANOTHER OVER CENTRAL PA, WITH MODEST  
TROUGHING EXTENDING BETWEEN THESE TWO LOWS. A WARM FRONT ALSO  
EXTENDS EAST-NORTHEASTWARD FROM THE CENTRAL PA ACROSS SOUTHERN NEW  
ENGLAND. THIS WARM FRONT IS DEMARCATED WELL BY THE 70 DEG F  
ISOTHERM.  
 
SCATTERED TO NUMEROUS THUNDERSTORMS ARE ANTICIPATED FROM THE  
SOUTHEAST INTO SOUTHERN NEW ENGLAND AS THE BOTH THE SURFACE  
TROUGHING AND PARENT UPPER TROUGH GRADUALLY PROGRESS EASTWARD. A  
BELT OF STRONGER MID-LEVEL FLOW CURRENTLY EXISTS THROUGHOUT THE  
EASTERN PERIPHERY OF THE UPPER TROUGH, EXTENDING ROUGHLY FROM  
CENTRAL MS INTO THE NORTHERN MID-ATLANTIC. NORTHERN PORTION OF THIS  
STRONGER MID-LEVEL FLOW WILL SPREAD GRADUALLY EASTWARD/NORTHEASTWARD  
THROUGHOUT THE DAY INTO MORE OF NEW ENGLAND WHILE THE SOUTHERN  
PORTION OVER THE SOUTHEAST AND MID-ATLANTIC WEAKENS.  
 
RATHER POOR LAPSE RATES ALOFT AND CLOUD COVER/ONGOING PRECIPITATION  
WILL DELAY/HINDER DIURNAL DESTABILIZATION ACROSS MUCH OF THE WARM  
SECTOR TODAY. A WEAKLY UNSTABLE AIRMASS IS STILL ANTICIPATED  
ALONG/AHEAD OF THE FRONT FROM THE MID-ATLANTIC NORTHWARD INTO  
SOUTHERN NEW ENGLAND, SUPPORTING CONTINUED THUNDERSTORM DEVELOPMENT  
THROUGH THE AFTERNOON/EARLY EVENING. GIVEN THE LARGELY LINE-PARALLEL  
ORIENTATION TO THE DEEP-LAYER SHEAR, A PREDOMINANTLY LINEAR STORM  
MODE IS ANTICIPATED. WEAK BUOYANCY COUPLED WITH THE STRENGTHENING  
MID-LEVEL FLOW COULD SUPPORT A RISK FOR DAMAGING GUSTS WITHIN ANY  
THUNDERSTORM CLUSTERS THAT DEVELOP.  
 
FORECAST WIND PROFILES DO SHOW SUFFICIENT LOW-LEVEL SHEAR FOR A  
TORNADO RISK WITH ANY MORE PERSISTENT, CELLULAR STORMS FROM EASTERN  
PA INTO SOUTHERN NY. HOWEVER, LIMITED DESTABILIZATION DUE TO  
ABUNDANT CLOUD COVER AND POOR LAPSE RATES SUGGESTS SHALLOW AND  
TRANSIENT WARM SECTOR UPDRAFTS, WITH LINEAR DEVELOPMENT ON THE FRONT  
MORE PROBABLE.  
   
..SOUTHWEST
 
 
THE WELL-DEFINED CYCLONE CURRENTLY MOVING ACROSS CENTRAL CA IS  
FORECAST TO CONTINUE SOUTHEASTWARD, EVENTUALLY INTERACTING WITH THE  
MOISTURE IN PLACE FROM EASTERN SOUTHERN CA AND THE LOWER CO VALLEY  
INTO WESTERN/SOUTHERN AZ. A MODEST INCREASE IN MID-LEVEL  
WEST-SOUTHWESTERLY FLOW SHOULD OCCUR AHEAD OF THIS CYCLONE THROUGH  
THE DAY, IN TANDEM WITH INCREASING LARGE-SCALE ASCENT OVERSPREADING  
PARTS OF THE SOUTHWEST. SCATTERED TO NUMEROUS THUNDERSTORMS ARE  
EXPECTED TO DEVELOP INITIALLY OVER THE HIGHER TERRAIN OF AZ, AND  
SUBSEQUENTLY DEVELOP SLOWLY NORTHWARD THROUGH THE EVENING. MODEST  
BUOYANCY AND SHEAR MAY SUPPORT AN ISOLATED HAIL/WIND THREAT WITH ANY  
MORE PERSISTENT CONVECTION THAT DEVELOPS, ESPECIALLY WHERE LOW-LEVEL  
LAPSE RATES CAN BECOME STEEPENED THROUGH DIURNAL HEATING/MIXING OF  
THE BOUNDARY LAYER.  
 

 
 
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