686
ACUS48 KWNS 070733
SWOD48
SPC AC 070732
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0232 AM CDT MON SEP 07 2026
VALID 101200Z - 151200Z
..DISCUSSION
AN UPPER SHORTWAVE TROUGH WILL WEAKEN AS IT SPREAD EAST ACROSS THE
NORTHEAST ON DAY 4/THURSDAY. AS THIS OCCURS, A SURFACE COLD FRONT
WILL SHIFT EAST/SOUTHEAST ACROSS THE NORTHEAST AND THE MID-ATLANTIC.
A MOIST AIRMASS WILL BE IN PLACE, BUT VERTICAL SHEAR WILL WEAKEN
THROUGH THE DAY AND DEEP-LAYER FLOW WILL REMAIN PARALLEL TO THE
SURFACE BOUNDARY. THUNDERSTORMS ARE EXPECTED IN THE VICINITY OF THE
FRONT, BUT MAY TEND TO BE JUST TO THE COOL SIDE OF THE BOUNDARY.
NEVERTHELESS, SOME LOW-END SEVERE POTENTIAL COULD DEVELOP FROM THE
OHIO VALLEY TO THE MID-ATLANTIC AS THE FRONT SAGS SOUTHWARD ACROSS
THE REGION.
DURING THE WEEKEND INTO EARLY NEXT WEEK, FORECAST GUIDANCE SUGGESTS
A MORE PROGRESSIVE UPPER PATTERN WILL EMERGE ACROSS THE NORTHERN
TIER OF THE U.S. A SERIES OF SHORTWAVE UPPER TROUGHS WILL MOVE FROM
THE NORTHERN ROCKIES TO THE GREAT LAKES AND EVENTUALLY THE NORTHEAST
DURING THIS TIME. SOME SEVERE RISK IS LIKELY TO DEVELOP AHEAD OF THE
UPPER SHORTWAVE TROUGHS AROUND THE DAY 5/FRIDAY TO DAY 8/MONDAY TIME
PERIOD. HOWEVER, LARGE SPREAD EXISTS IN BOTH THE TIMING AND
INTENSITY OF THESE UPPER TROUGH, RESULTING IN VASTLY DIFFERENT
EVOLUTION AND TIMING OF KEY SURFACE FEATURES (MAINLY SURFACE LOW
POSITION). THESE DIFFERENCES HAVE LARGE IMPLICATIONS FOR WHERE THE
BEST CORRIDORS OF SEVERE POTENTIAL WILL ULTIMATELY DEVELOP, BUT
SEVERE PROBABILITIES MAY BECOME NECESSARY IN LATER OUTLOOKS FOR
PORTIONS THE NORTHERN/CENTRAL PLAINS TO THE UPPER MIDWEST DURING THE
WEEKEND.
..LEITMAN.. 09/07/2026
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page