994
ACUS48 KWNS 180759
SWOD48
SPC AC 180757
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 AM CDT SAT JUL 18 2026
VALID 211200Z - 261200Z
..DISCUSSION
..DAY 4-5/TUE-WED -- OHIO VALLEY TO MID-ATLANTIC VICINITY
AN UPPER TROUGH WILL PIVOT ACROSS THE REGION ON TUESDAY AND
WEDNESDAY, BRINGING ENHANCED SOUTHERLY FLOW ALOFT AS A SURFACE COLD
FRONT SWEEPS EAST/SOUTHEAST THROUGH WEDNESDAY NIGHT. AHEAD OF THE
SURFACE FRONT, RICH BOUNDARY LAYER MOISTURE WILL BE IN PLACE, AND AT
LEAST MODERATE DESTABILIZATION SHOULD OCCUR. CONVECTION COULD BE
ONGOING TUESDAY MORNING ACROSS PARTS OF IL/IN/LOWER MI/WESTERN OH.
THE EXTENT OF THIS ACTIVITY IS UNCLEAR AND WILL DEPEND ON THE
EVOLUTION OF ANY POTENTIAL MCS IN THE DAY 3 PERIOD. NEVERTHELESS,
THE DOWNSTREAM AIRMASS ACROSS PARTS OF THE OHIO VALLEY WILL BECOME
FAVORABLE FOR SCATTERED SEVERE THUNDERSTORMS TUESDAY AFTERNOON AND
EVENING, LIKELY IN THE FORM OF ONE OR MORE LINE SEGMENTS ORGANIZING
AHEAD OF THE ADVANCING COLD FRONT. AN ADDITIONAL AREA OF SEVERE
STORMS WILL BE POSSIBLE ON TUESDAY ACROSS THE MID-ATLANTIC WITHIN A
WARM ADVECTION REGIME AHEAD OF THE APPROACHING SYSTEM OVER THE OHIO
VALLEY. SOME AREAS COULD SEE MORE THAN ONE ROUND OF SEVERE
THUNDERSTORMS ON TUESDAY/TUESDAY NIGHT.
BY WEDNESDAY, THE SEVERE RISK SHOULD SPREAD EAST FROM THE
MID-ATLANTIC INTO THE CAROLINAS AS THE UPPER TROUGH AND SURFACE COLD
FRONT CONTINUE TO SHIFT EAST. IT IS UNCERTAIN HOW FAR NORTH THE
SEVERE RISK MAY EXTEND AND PROBABILITIES MAY EVENTUALLY NEED TO BE
INCLUDED ACROSS PARTS OF THE NORTHEAST/NEW ENGLAND. WHERE STORMS DO
FORM, DAMAGING WINDS WILL BE POSSIBLE UNTIL THE COLD FRONT MOVES
OFFSHORE WEDNESDAY EVENING/NIGHT.
..DAYS 6-8/THU-SAT
UPPER TROUGHING WILL PERSIST ACROSS THE EASTERN U.S. THROUGH THE END
OF THE FORECAST PERIOD, BUT DEEP-LAYER FLOW WILL WEAKEN. HIGH
PRESSURE IN THE WAKE OF THE COLD FRONTAL PASSAGE WILL PRECLUDE
SEVERE POTENTIAL ACROSS THE OHIO VALLEY INTO THE MID-ATLANTIC AND
NORTHEAST THURSDAY THROUGH SATURDAY.
ACROSS THE PLAINS AND WESTERN U.S., A STRONG UPPER ANTICYCLONE WILL
PARK OVER THE SOUTHERN PLAINS, WITH AN AMPLIFIED UPPER RIDGE
BUILDING INTO THE NORTHERN ROCKIES. SOME THUNDERSTORM POTENTIAL
COULD DEVELOP ACROSS PARTS OF THE PLAINS AS LOW-LEVEL MOISTURE
INCREASES BENEATH THE RIDGE. HOWEVER, SEVERE POTENTIAL IS UNCERTAIN
AS ANY POTENTIAL WOULD BE DRIVEN BY MESOSCALE FEATURES NOT WELL
DEFINED AT THIS TIME FRAME, AND AS THE UPPER RIDGE SUPPRESSES ANY
LARGE-SCALE SUPPORT FOR ORGANIZED SEVERE THUNDERSTORMS.
..LEITMAN.. 07/18/2026
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