801
ACUS02 KWNS 130601
SWODY2
SPC AC 130600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT MON JUL 13 2026
VALID 141200Z - 151200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
NEW ENGLAND...
..SUMMARY
SEVERE THUNDERSTORMS WILL BE POSSIBLE DURING THE AFTERNOON AND
EVENING ACROSS PORTIONS OF NEW ENGLAND ON TUESDAY. ADDITIONAL
STRONG-TO-SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS PARTS OF
WESTERN AND CENTRAL MONTANA.
.. SYNOPSIS
THE EXPANSIVE MID-LEVEL RIDGE CENTERED ACROSS THE NORTH-CENTRAL
UNITED STATES WILL BEGIN TO QUICKLY RETROGRADE ON TUESDAY IN
RESPONSE TO A STRONG SHORT-WAVE TROUGH DIGGING SOUTHEAST ACROSS THE
NORTHEAST. ENHANCED MID-LEVEL FLOW WILL SURROUND THE CENTER OF THIS
MID-LEVEL RIDGE, WITH MULTIPLE VORTICITY/SPEED MAXIMA MOVING THROUGH
THIS ENHANCED FLOW.
.. NEW ENGLAND
A STRONG SHORT-WAVE TROUGH WILL MOVE ACROSS NEW ENGLAND DURING THE
EVENING AND OVERNIGHT HOURS. AHEAD OF THIS TROUGH, SOUTHWESTERLY
LOW-LEVEL FLOW WILL ALLOW TEMPERATURES TO WARM INTO THE 80FS AND
90FS ACROSS NORTHERN NEW ENGLAND. ADDITIONALLY, THE ORIENTATION OF
THE LOW-LEVEL FLOW WILL ALLOW RICH BOUNDARY LAYER MOISTURE TO ADVECT
NORTHEASTWARD, THROUGH THE ST. LAWRENCE VALLEY, AND INTO NORTHERN
NEW ENGLAND. (HREF ENSEMBLE MEAN DEWPOINTS ARE GREATER THAN 70F
ACROSS NORTHERN NEW YORK INTO WESTERN MAINE.) THE COMBINATION OF A
WARM, MOIST BOUNDARY LAYER AND MODEST MID-LEVEL LAPSE RATES SHOULD
YIELD STRONG INSTABILITY BY THE AFTERNOON, WITH HREF PROBABILITIES
OF EXCEEDING 2000 J/KG MUCAPE GREATER THAN 50% ACROSS PORTIONS OF
THE AREA.
THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG AND AHEAD OF AN
APPROACHING SURFACE COLD FRONT DURING THE AFTERNOON WITHIN THE ST.
LAWRENCE VALLEY. AT THE SAME TIME, VERTICAL WIND SHEAR WILL BE
INCREASING THROUGHOUT THE DAY AS THE MID-LEVEL TROUGH APPROACHES.
GIVEN STRONG INSTABILITY AND EFFECTIVE-LAYER SHEAR IN EXCESS OF 50
KNOTS BY LATE AFTERNOON, MULTIPLE CLUSTERS OF SEVERE STORMS ARE
EXPECTED NORTH OF NEW ENGLAND. THESE STORMS WILL EVENTUALLY GROW
UPSCALE INTO ONE OR MORE LINEAR CLUSTERS AS THEY MOVE INTO AND
ACROSS PORTIONS OF NEW ENGLAND DURING THE LATE AFTERNOON, EVENING,
AND OVERNIGHT.
GIVEN THE DEGREE OF INSTABILITY AND STRENGTH OF THE FLOW, SEVERE
THUNDERSTORM WINDS ARE LIKELY (SOME SIGNIFICANT). LARGE HAIL WILL
ALSO BE POSSIBLE WITH ANY STORMS. ADDITIONALLY, FORECAST SOUNDINGS
SHOW ENOUGH LOW-LEVEL CURVATURE TO SUPPORT A TORNADO THREAT,
INCLUDING A STRONG TORNADO OR TWO, WITH ANY SUSTAINED SURFACE-BASED
SUPERCELL.
.. PORTIONS OF WESTERN AND CENTRAL MONTANA
STRONG MID-LEVEL FLOW WILL PERSIST ACROSS THE NORTHERN ROCKIES,
BRINGING AN INFLUX OF LOW- AND MID-LEVEL MOISTURE COMPARED TO RECENT
DAYS. AN EMBEDDED SHORTWAVE TROUGH MOVING ACROSS THE REGION WILL
COMBINE WITH DAYTIME HEATING OVER THE HIGHER TERRAIN TO SUPPORT
WIDELY SCATTERED TO SCATTERED THUNDERSTORMS. HOWEVER, INCREASING
CLOUD COVER MAY LIMIT THESE STORMS FROM FULLY ROOTING IN THE
BOUNDARY LAYER. DESPITE THIS LIMITATION, THE STRONGEST STORMS WILL
BE CAPABLE OF PRODUCING SEVERE WIND GUSTS AND MARGINALLY SEVERE
HAIL.
..MARSH.. 07/13/2026
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