USA Weather — Severe Weather Division
This outlook is expired and is no longer valid.
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING ACROSS THE ARKLATEX AND DEEP SOUTH INTO THE FLORIDA EAST COAST...AND OVER ACROSS CENTRAL MINNESOTA INTO NORTHWEST WISCONSIN...
...SUMMARY...
WIDESPREAD THUNDERSTORMS WILL CONTINUE ACROSS MUCH OF THE SOUTHEAST. A CORRIDOR OF SCATTERED SEVERE WINDS EXTENDING FROM THE ARKLATEX INTO THE SOUTHEAST WILL DEVELOP THIS AFTERNOON, WITH LOCALLY SEVERE WIND GUSTS AND BRIEFLY SEVERE HAIL POSSIBLE ELSEWHERE ACROSS THE SOUTH. SCATTERED SEVERE WINDS, LARGE HAIL, AND A TORNADO OR TWO ARE FORECAST ACROSS THE UPPER MIDWEST THIS AFTERNOON AND EVENING. DAMAGING WIND GUSTS WILL ALSO BE A CONCERN THIS AFTERNOON AND TONIGHT ACROSS PARTS OF THE GREAT BASIN AND OVER THE SOUTHERN TO CENTRAL HIGH PLAINS.
...SOUTHEAST...
A WEAK COLD FRONT CURRENTLY EXTENDING FROM THE EASTERN CAROLINAS INTO THE ARKLATEX WILL SLOWLY SAG SOUTHWARD TODAY. AN EXTREMELY MOIST TROPICAL AIRMASS WITH PWATS IN EXCESS OF 2.2 TO 2.5” EXISTS ALONG AND SOUTH OF THE FRONT CONTRIBUTING TO SURFACE DEWPOINTS IN THE UPPER 70S TO LOW 80S FROM EASTERN TEXAS AND ACROSS THE DEEP SOUTH AND SOUTHEAST. INTENSE DIURNAL HEATING AHEAD OF ONGOING CONVECTION IS ALLOWING FOR TEMPERATURES TO QUICKLY RISE WELL INTO THE 90S. GIVEN MODERATE MID-LEVEL LAPSE RATES IN THE 6.5 TO 7.0 C/KM RANGE NOTED IN MORNING RAOBS, VERY STRONG INSTABILITY IS DEVELOPING WITHIN THE HOT AND MOIST AIRMASS, WITH MLCAPES IN THE 3000-4000 J/KG RANGE NOTED ACROSS THE REGION IN RECENT MESOANALYSIS, AND COULD INCREASE TO 5000 J/KG BY THIS AFTERNOON, ESPECIALLY FROM NORTHERN LOUISIANA INTO THE CENTRAL GULF COAST REGION WHERE THE BETTER MID-LEVEL LAPSE RATES WERE NOTED, AS WELL AS LOW-LEVELS TO EXCEED 7.0 C/KM.
DESPITE WEAK TO MODEST SHEAR OF 20-25KT TODAY, THE STRONG SURFACE CONVERGENCE ALONG AND AHEAD OF THE FRONT, COLLIDING OUTFLOW BOUNDARIES AND THE SEABREEZE, AS WELL AS THE VERY STRONG HEATING HAS ALREADY RESULTED IN A BAND OF INTENSIFYING STORMS EXTEND FROM THE ARKLATEX INTO SOUTHERN GEORGIA. AS STORMS CONTINUE TO SPREAD SOUTHEASTWARD TODAY WITHIN THE INCREASINGLY UNSTABLE/MOIST AIRMASS, ISOLATED TO SCATTERED SEVERE/DAMAGING WINDS SHOULD OCCUR DUE TO A FAVORABLE MICROBURST ENVIRONMENT. IT ALSO APPEARS THAT A FEW LOOSELY ORGANIZED CLUSTERS ALONG CONGLOMERATE OUTFLOW COULD PRODUCE A FEW CORRIDORS FOR GREATER COVERAGE OF SEVERE WIND GUSTS, ESPECIALLY WHERE MULTIPLE STORM CELLS MERGE. A BROAD SLIGHT RISK FOR WIND HAS BEEN INTRODUCED FOR THESE STORMS. A FEW ISOLATED INSTANCES OF BRIEF MARGINALLY SEVERE HAIL ALSO APPEARS POSSIBLE WHERE VERY TALL UPDRAFTS CAN OCCUR, THOUGH RATHER HIGH FREEZING HEIGHTS AND THE MOIST AIRMASS WILL BE A SIGNIFICANT LIMITING FACTOR OF HAIL POTENTIAL. FURTHER WEST ACROSS EAST TEXAS, A SIMILARLY MOIST/UNSTABLE AIRMASS WILL EXIST AHEAD OF MULTIPLE BANDS OF EASTWARD ADVANCING CONVECTION. HOWEVER, CLOSER PROXIMITY TO A WEAK MID-LEVEL RIDGE CENTERED NEAR THE UPPER TEXAS COAST MAY LIMIT STORM COVERAGE AND INTENSITY. STILL, ISOLATED SEVERE DOWNBURST WINDS AND PERHAPS BRIEFLY SEVERE HAIL WILL EXIST WITHIN ANY MORE INTENSE STORMS.
...UPPER MIDWEST...
A CLIPPER-LIKE SYSTEM CURRENTLY NOTED OVER NORTH DAKOTA IS QUICKLY MOVING EAST SOUTHEAST INTO THE UPPER MIDWEST, WITH A WEAK SURFACE LOW AND TRAILING COLD FRONT NOTED UNDERNEATH IT. AS THIS FEATURE MOVES INTO THE UPPER MIDWEST BY THIS AFTERNOON, MODEST MLCAPE TO AROUND 1000 J/KG SHOULD DEVELOP AS A RESULT OF SUFFICIENT HEATING UNDERNEATH FAIRLY STEEP LAPSE RATES DRIVEN BY COOLING MID-LEVEL TEMPERATURES. SCATTERED THUNDERSTORM CLUSTERS SHOULD DEVELOP NEAR THE FRONT AND SURFACE LOW THIS AFTERNOON AND SPREAD SOUTHEAST INTO THE EVENING HOURS. MODERATE TO STRONG DEEP-LAYER SHEAR OF 45-55KT, AS WELL AS INTENSIFYING LOW-LEVEL HELICITY OF 100-150 M2/S2, PERHAPS HIGHER ON THE SOUTHEASTERN PARTS OF THE RISK AREA (I.E. SOUTHERN MINNESOTA INTO WISCONSIN), WILL SUPPORT ORGANIZING BANDS AND PERHAPS A COUPLE OF LOW-TOPPED SUPERCELLS. SCATTERED DAMAGING WINDS AND ISOLATED HAIL CURRENTLY APPEAR TO BE THE GREATEST THREAT GIVEN STEEP LAPSE RATES, THOUGH A COUPLE BRIEF TORNADOES MAY ALSO EVOLVE WHERE THE GREATEST LOW-LEVEL HELICITY MAY EVOLVE.
...GREAT BASIN...
AHEAD OF AN UPPER LOW CENTERED WELL OFFSHORE NORTHERN CALIFORNIA, A BELT OF MODERATE TO STRONG SOUTHERLY MID-LEVEL FLOW WILL CONTINUE OVERSPREADING PARTS OF THE GREAT BASIN, ESPECIALLY NORTHERN CALIFORNIA AND NEVADA. A VERY HOT AND DEEPLY MIXED AIRMASS, WITH NEARLY DRY ADIABATIC LAPSE RATES, WILL CONTRIBUTE TO MODERATE INSTABILITY DEVELOPING TODAY. AS HEIGHT FALLS COINCIDE WITH PEAK HEATING, SCATTERED HIGH-BASED, DRY THUNDERSTORMS SHOULD DEVELOP AND SPREAD NORTHWARD THIS AFTERNOON AND EVENING. WITH STRONG ENOUGH SHEAR SUPPORTIVE OF THIS CONVECTION TO OCCASIONALLY ORGANIZE AND BECOME LINEAR, ISOLATED INTENSE DRY MICROBURST WINDS APPEAR TO BE POSSIBLE WITHIN STRONGER STORMS. GIVEN THE INTENSE MIXING, WINDS >75MPH CANNOT BE RULED OUT WITH THESE MICROBURSTS.
...SOUTHERN/CENTRAL HIGH PLAINS...
ISOLATED HIGH-BASED CONVECTION DEVELOPS THIS AFTERNOON AND EVENING ON THE FRONT RANGE OF THE ROCKIES DRIVEN BY STRONG LOW0LEVEL CONVERGENCE AND OROGRAPHIC LIFT. MODERATE NORTHWESTERLY FLOW ALONG WITH A WELL MIXED BOUNDARY LAYER MAY SUPPORT AN ISOLATED DAMAGING WIND OUTFLOW/DOWNBURST WIND THREAT DURING THE AFTERNOON AND EVENING. OVERNIGHT, INCREASING WARM AIR ADVECTION WILL CONTRIBUTE TO ELEVATED INSTABILITY ACROSS THE CENTRAL PLAINS, POTENTIALLY WITH MUCAPE EXCEEDING 2000 J/KG, ALONG WITH INTENSE DEEP-LAYER SHEAR. SCATTERED ELEVATED CONVECTION SHOULD DEVELOP WITH THE WARM AIR ADVECTION REGIME OVERNIGHT. AFOREMENTIONED THERMODYNAMIC/KINEMATIC PROFILES COULD SUPPORT A THREAT FOR OCCASIONALLY STRONG ENOUGH ELEVATED UPDRAFTS TO PRODUCE A LARGE HAIL THREAT TOWARDS THE END OF THE PERIOD.