Significant Severe Weather Outbreak On Tap for Friday, March 2nd (3/1/2012)


THIS IS THE DAY 2 CONVECTIVE OUTLOOK FROM THE STORM PREDICTION CENTER. KEEP IN MIND THAT SINCE WE HAD A SIGNIFICANT SEVERE WEATHER OUTBREAK FROM THE EVENING OF TUESDAY, FEBRUARY 28 TO THE EVENING OF WEDNESDAY, FEBRUARY 29, WE NEED TO TAKE NOTICE. THIS EVENT FOR TOMORROW WILL BE MORE SIGINIFICANT THAN THE OUTBREAK I HAD JUST MENTIONED.

 

NOW THE DAY 2 CONVECTIVE OUTLOOK FOR FRIDAY, MARCH 2ND, 2012

..THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF MISSISSIPPI, ALABAMA, TENNESSEE, KENTUCKY, INDIANA, AND OHIO. THERE IS ALSO A SLIGHT RISK OF SEVERE THUNDERSTORMS ELSEWHERE FROM THE ARKLAMISS REGION EASTNORTHEASTEASTWARD TO THE CAROLINAS AND NORTHWESTWARD TO SOUTHWESTERN PENNSYLVANIA, INDIANA AND THE OZARKS.

SYNOPSIS: AN UPPER-AIR PATTERN TRANSITION IS UNDERWAY AT THE MOMENT, WITH HEIGHT FALLS    ACROSS MUCH OF WRN CONUS IN ADVANCE OF SYNOPTIC SCALE TROUGH DEVELOPMENT.  RESULT THROUGH DAY-1 WILL BE BROADLY CYCLONIC FLOW ACROSS MOST OF WRN CONUS, MOVING EWD TO CENTRAL CONUS DAY-2.  BY START OF PERIOD, EXPECT NRN-STREAM MID-UPPER CYCLONE LOCATED OVER NORTH DAKOTA/MANITOBA BORDER REGION, AND BASAL 500-MB SHORTWAVE TROUGH OVER THE 4-CORNERS REGION. DOWNSTREAM FROM THAT PERTURBATION, LOWER-AMPLITUDE SHORTWAVE SHOULD BE MOVING ENE-WD ACROSS KANSAS.  VORTICITY FIELDS WITH LATTER TWO SHORTWAVES SHOULD REMAIN WELL-CONNECTED, EFFECTIVELY RESULTING IN POSITIVELY TILTED TROUGH FROM EASTERN IOWA/NORTHERN ILLINOIS REGION TO EASTERN NEW MEXICO BY 3/00Z. BY 3/12Z, EXPECT MID-UPPER LOW OVER LAKE HURON OR ADJOINING PORTIONS OF ONTARIO, CANADA. WITH TROUGH SWWD OVER LOWEST SEGMENT OF OHIO RIVER, OKLAHOMA, AND SOUTHERN NEW MEXICO. AT THE SURFACE, A COLD FRONT NOW IMPINGING ON THE SOUTHWESTERN APPALACHIANS/TENNESSEE VALLEY/NORTHERN LOUISIANA SHOULD MOVE BACK NORTH AS A WARM FRONT DURING THIS PERIOD, THE WESTERN PORTION OF WHICH WILL ATTACH WITH A SURFACE FRONTAL-WAVE LOW OVER MO BY 2/12Z. LOW PRESSURE WILL DEEPEN AND MOVE NEWD TOWARD SOUTHERN LOWER MICHIGAN BY 3/00Z. THEN OCCLUDE AND BECOME STACKED WITH MIDLEVEL VORTEX BY END OF PERIOD. WARM FRONT SHOULD MOVE NEWD OVER THE MID-UPPER OHIO VALLEY AND CENTRAL APPALACHIANS THROUGH PERIOD. A COLD FRONT TRAILING SURFACE LOW SHOULD START PERIOD OVER THE OZARKS, SOUTHEASTERN OKLAHOMA AND WEST-CENTRAL TEXAS.  BY 3/00Z, A COLD FRONT SHOULD REACH EASTERN INDIANA/WESTERN OHIO, SOUTHEASTERN ARKANSAS, AND THE MIDDLE TEXAS COASTAL PLAIN. BY 3/12Z, THE COLD FRONT SHOULD REACH CENTRAL/EASTERN PENNSYLVANIA, WESTERN VIRGINIA, NORTHERN GEORGIA, AND SOUTHERN ALABAMA.

AREAS FROM THE OZARKS TO THE LOWER MISSISSIPPI/TENNESSEE VALLEY AND ALABAMA TO THE OHIO RIVER VALLEY STATES: SCATTERED ELEVATED THUNDERSTORMS IN CLUSTERS MAY BE CARRY OVER FROM LATE DAY-1 PERIOD OVER PORTIONS OF THE OZARKS, LOWER OHIO RIVER VALLEY AND MID-SOUTH REGIONS WITH FAVORABLE CAPE ALOFT AND DEEP-LAYER SHEAR FOR HAIL. SOME OF THIS ACTIVITY MAY PERSIST LONG ENOUGH TO BECOME SURFACE-BASED BY MIDDAY AND EARLY AFTERNOON IN INCREASINGLY FAVORABLE ENVIRONMENT FOR SEVERE. OTHER SCATTERED-NUMEROUS THUNDERSTORMS SHOULD DEVELOP ALONG/AHEAD OF THE COLD FRONT. THUNDERSTORMS SHOULD BE AND WILL BE FAST-MOVING, ABLE TO COVER LONG SWATHS WITH THEIR SEVERE THREATS OVER ANY GIVEN PERIOD OF TIME. THE AIR MASS AHEAD OF A SURFACE COLD FRONT AND IN WAKE OF MORNING CONVECTION SHOULD DESTABILIZE FAVORABLY AMIDST STRONG LOW-LEVEL WAA/MOISTURE TRANSPORT. INTENSE DEEP-LAYER SHEAR AND LOW-LEVEL HODOGRAPHS WILL SPREAD OVER MUCH OF WARM SECTOR, ALONG WITH SURFACE DEW POINTS INCREASING FROM MID 50S OVER OH TO MID 60S OVER PORTIONS MISSISSIPPI/ALABAMA. IN TANDEM WITH DIURNAL SURFACE HEATING, THIS SHOULD SUPPORT MLCAPE 250-500 J/KG OVER PORTIONS OF OHIO/INDIANA, TO 1500-2000 J/KG RANGE OVER PORTIONS OF TENNESSEE/KENTUCKY, THEN DECREASING SOMEWHAT FARTHER SOUTH DUE TO INFLUENCES OF STABLE LAYERS ALOFT. DESPITE UNCERTAINTIES REGARDING EXTENT/COVERAGE OF VARIOUS CONVECTIVE MODES THIS FAR OUT, EXPECT WEAK CINH, BROADLY FAVORABLE CAPE/SHEAR PARAMETER SPACE, AND RELATIVELY DENSE COVERAGE OF CONVECTION LIKELY TO IMPINGE ON THAT    SETTING. AS SUCH, NUMEROUS SVR WIND EVENTS ARE POSSIBLE ALONG WITH POTENTIAL FOR STG TORNADOES FROM EITHER SUPERCELLS OR QLCS-VORTEX MECHANISMS. AT LEAST A FEW WIND EVENTS AOA 65 KT AND LONG-TRACK/SIGNIFICANT TORNADOES ARE POSSIBLE.  THEREFORE, SIGNIFICANT SEVERE AREA IS BEING INTRODUCED, DRIVING CATEGORICAL MODERATE RISK WHERE OVERLAID WITH RELATIVELY DENSE 45% TOTAL-SVR PROBABILITY.

NORTH/SOUTH CAROLINA: INITIALLY SEPARATE SVR POTENTIAL MAY DEVELOP OVER THIS REGION DURING AFTERNOON/EVENING, WHICH MAY CONNECT WITH EASTERN FRINGES OF LARGER SEVERE AREA LATE IN PERIOD AS LATTER REGIME SHIFTS EASTWARD. SOUTHERN BRANCH OF STG MID-UPPER LEVEL FLOW WILL SPREAD OVER INCREASINGLY FAVORABLE  BOUNDARY-LAYER THETAE ASSOCIATED WITH THE RETREATING WARM FRONT. PRIMARY UNCERTAINTIES ATTM RESIDE IN STRENGTH OF LOW-LEVEL LIFT, AND THEREFORE CONVECTIVE COVERAGE. HOWEVER, DIURNAL HEATING, PRESENCE OF REASONABLY WELL-DEFINED FRONTAL ZONE. AND WEAK MLCINH SHOULD PERMIT WIDELY SCATTERED TO SCATTERED THUNDERSTORMS TO DEVELOP IN REGIME OF 60S F WARM-SECTOR DEW POINTS. ACCORDINGLY, ADJUSTED FORECAST SOUNDINGS SUGGEST 1000-1500 J/KG LATE-AFTERNOON MLCAPE POSSIBLE, JUXTAPOSED WITH 50-60 KT EFFECTIVE SHEAR MAGNITUDES.  MAIN THREAT MAY BE DAMAGING WIND, WITH ISOLATED HAIL ALSO EXPECTED. FORECAST HODOGRAPHS ALSO ARE FAVORABLE FOR SUPERCELL/TORNADO RISK, MAIN QUESTIONS BEING COVERAGE/DURATION OF FAVORABLE STORM MODES.   

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