USA Weather — Severe Weather Division
This outlook is expired and is no longer valid.
...THERE IS A SLIGHT RISK ACROSS PORTIONS OF THE CENTRAL PLAINS...MID-MISSISSIPPI VALLEY...MIDWEST...AND OHIO VALLEY...
...THERE IS AN ENHANCED RISK ACROSS MUCH OF THE MID-MISSISSIPPI VALLEY INTO THE OHIO VALLEY...
...THE POTENTIAL EXISTS FOR A WIDESPREAD SEVERE WEATHER EVENT ON WEDNESDAY AND WEDNESDAY NIGHT. WIDESPREAD DAMAGING WINDS MAY BECOME THE PRIMARY HAZARD WITH TIME...ALTHOUGH LARGE HAIL AND TORNADOES WILL ALSO BE POSSIBLE...
...SYNOPSIS...
A HIGH-AMPLITUDE UPPER-LEVEL TROUGH IS FORECAST TO EJECT NORTHEASTWARD FROM THE CENTRAL PLAINS INTO THE UPPER MIDWEST AND GREAT LAKES REGION ON WEDNESDAY. AS THIS OCCURS...THE TROUGH IS EXPECTED TO ACQUIRE A NEGATIVE TILT WHILE A POWERFUL MID-LEVEL JET STREAK TRANSLATES ACROSS THE MID-MISSISSIPPI VALLEY AND MIDWEST. STRONG HEIGHT FALLS AND INCREASING LARGE-SCALE ASCENT WILL OVERSPREAD A BROAD WARM SECTOR ACROSS THE CENTRAL AND EASTERN UNITED STATES THROUGH THE DAY.
AT THE SURFACE...A DEEPENING CYCLONE IS EXPECTED TO TRACK FROM THE UPPER MIDWEST TOWARD THE GREAT LAKES REGION WHILE A STRONG COLD FRONT SURGES EASTWARD ACROSS THE MID-MISSISSIPPI VALLEY. SOUTH OF THE LOW...A STRENGTHENING LOW-LEVEL JET WILL TRANSPORT RICH GULF MOISTURE NORTHWARD INTO THE WARM SECTOR. SURFACE DEWPOINTS WELL INTO THE 60S AND 70S APPEAR LIKELY ACROSS A LARGE PORTION OF THE REGION BY PEAK HEATING.
THE COMBINATION OF STRONG FORCING FOR ASCENT...INTENSIFYING LOW-LEVEL MASS RESPONSE...AND INCREASING INSTABILITY WILL SUPPORT THE DEVELOPMENT OF ORGANIZED THUNDERSTORMS ALONG AND AHEAD OF THE ADVANCING COLD FRONT. FORECAST KINEMATIC FIELDS SUGGEST A FAVORABLE ENVIRONMENT FOR SUPERCELLS AND ORGANIZED CONVECTIVE SYSTEMS CAPABLE OF PRODUCING ALL MODES OF SEVERE WEATHER.
AS THE SURFACE CYCLONE DEEPENS AND THE LOW-LEVEL JET STRENGTHENS THROUGH THE AFTERNOON AND EVENING HOURS...THE POTENTIAL WILL EXIST FOR THUNDERSTORMS TO CONSOLIDATE INTO ONE OR MORE FAST-MOVING MESOSCALE CONVECTIVE SYSTEMS. THE EVOLUTION OF CONVECTIVE MODE WILL PLAY A CRITICAL ROLE IN DETERMINING THE LOCATION AND MAGNITUDE OF THE GREATEST SEVERE WEATHER THREAT.
WHILE IMPORTANT MESOSCALE DETAILS REMAIN UNCERTAIN...CONFIDENCE IS INCREASING IN A FAVORABLE SYNOPTIC ENVIRONMENT FOR A WIDESPREAD SEVERE WEATHER EVENT ACROSS PORTIONS OF THE MID-MISSISSIPPI VALLEY INTO THE OHIO WEDNESDAY.
...MID-MISSISSIPPI VALLEY INTO THE OHIO VALLEY...
A POTENTIALLY SIGNIFICANT SEVERE WEATHER EVENT MAY UNFOLD ACROSS THE MID-MISSISSIPPI VALLEY INTO THE OHIO VALLEY ON WEDNESDAY AS A POWERFUL MID-LATITUDE CYCLONE DEVELOPS ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. A NEGATIVELY-TILTED UPPER-LEVEL TROUGH IS FORECAST TO EJECT NORTHEASTWARD THROUGH THE PERIOD...RESULTING IN STRONG HEIGHT FALLS...INCREASING LARGE-SCALE ASCENT...AND A FAVORABLE KINEMATIC ENVIRONMENT FOR ORGANIZED SEVERE THUNDERSTORMS.
AT THE SURFACE...A DEEPENING AREA OF LOW PRESSURE IS FORECAST TO TRACK FROM THE MIDWEST TOWARD THE GREAT LAKES WHILE A STRONG COLD FRONT ADVANCES EASTWARD ACROSS THE MID-MISSISSIPPI VALLEY. A STRENGTHENING LOW-LEVEL JET WILL TRANSPORT RICH GULF MOISTURE NORTHWARD INTO A BROAD WARM SECTOR CHARACTERIZED BY MODERATE TO STRONG DESTABILIZATION. FORECAST SOUNDINGS CONTINUE TO INDICATE A FAVORABLE COMBINATION OF INSTABILITY...LOW-LEVEL SHEAR...AND DEEP-LAYER FLOW SUPPORTIVE OF ORGANIZED SUPERCELLS AND BOWING CONVECTIVE SEGMENTS.
THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG AND AHEAD OF THE ADVANCING COLD FRONT DURING THE AFTERNOON HOURS. INITIAL CONVECTIVE MODES MAY INCLUDE DISCRETE OR SEMI-DISCRETE SUPERCELLS CAPABLE OF ALL SEVERE HAZARDS. WITH TIME...INCREASING FORCING FOR ASCENT AND STORM INTERACTIONS MAY PROMOTE UPSCALE GROWTH INTO ONE OR MORE ORGANIZED MESOSCALE CONVECTIVE SYSTEMS.
OF PARTICULAR INTEREST IS THE POTENTIAL FOR A FAST-MOVING CONVECTIVE SYSTEM TO EVOLVE DURING THE EVENING AND OVERNIGHT HOURS AS A STRONG LOW-LEVEL JET INTERACTS WITH AN EXPANDING COLD POOL. CURRENT GUIDANCE SUGGESTS CONVECTION MAY CONSOLIDATE AND PROPAGATE EAST-SOUTHEASTWARD FROM THE MID-MISSISSIPPI VALLEY TOWARD THE OHIO VALLEY. SHOULD THIS EVOLUTION OCCUR...THE THREAT MAY TRANSITION TOWARD WIDESPREAD DAMAGING WINDS WITH EMBEDDED TORNADOES AND SWATHS OF SIGNIFICANT WIND DAMAGE POSSIBLE.
WHILE IMPORTANT MESOSCALE DETAILS REMAIN UNCERTAIN...CONFIDENCE IS INCREASING IN A FAVORABLE SYNOPTIC ENVIRONMENT FOR ORGANIZED SEVERE THUNDERSTORMS ACROSS THE MID-MISSISSIPPI VALLEY INTO THE OHIO VALLEY ON WEDNESDAY. CURRENT THREAT SUPPORTS ENH CIG 2 PROBABILITY WITH UPGRADES LIKELY IN SUBSEQUENT OUTLOOKS.