2008

Mesoscale Discussion #0045


CONCERNING...OUTLOOK UPGRADE 

   

VALID 101523Z - 101630Z

   

...MODERATE RISK WILL BE ISSUED SHORTLY FOR PORTIONS OF MS/AL/TN...

   

RAPID BOUNDARY LAYER RECOVERY ACROSS THE NRN GULF STATES INTO MIDDLE TN WILL GENERATE SUFFICIENT INSTABILITY FOR ROBUST SUPERCELL DEVELOPMENT.  STRONG SHEAR WILL BE SUPPORTIVE OF TORNADOES IN ADDITION TO DAMAGING WINDS.

Mesoscale Discussion #0046


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 16 CONTINUES.

   

...TORNADO THREAT APPEARS TO BE INCREASING ACROSS PORTIONS OF SERN LA AND SRN MS...

   

HIGHER THETA-E AIRMASS HAS SPREAD INLAND ACROSS SRN LA/MS WHERE SFC DEW POINTS ARE NOW INTO THE UPPER 60S.  WITH BREAKS NOW EVIDENT IT APPEARS INSTABILITY WILL ONLY IMPROVE ACROSS THIS REGION ENHANCING THE PROSPECT FOR ROBUST UPDRAFT DEVELOPMENT.  LATEST RADAR DATA SUPPORTS THIS WITH ONE STRONG SUPERCELL HAVING DEVELOPED OVER EAST FELICIAN PARISH IN LA.  WITH MINIMAL INHIBITION AND SHEAR INCREASING ACROSS THIS REGION ANY PREFRONTAL DISCRETE SUPERCELLS HAVE THE POTENTIAL TO BE LONG-LIVED.  TORNADO THREAT IS INCREASING ACROSS THIS REGION AND A NEW TORNADO WATCH MAY BE REQUIRED DOWNSTREAM INTO SERN MS.

Mesoscale Discussion #0052


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 17 CONTINUES.

   

A LINE OF STRONG TO SEVERE THUNDERSTORMS WILL CONTINUE TO ADVANCE EWD ACROSS ERN AL AND NW GA LATE THIS AFTERNOON INTO EARLY THIS EVENING. TORNADOES AND WIND DAMAGE WILL BE POSSIBLE WITH THE MORE INTENSE STORMS. LATEST SFC ANALYSIS SHOWS A COLD FRONT EXTENDING SWD FROM WRN TN INTO NW MS WITH A MOIST AXIS WITH 60 TO 65 DEGREE SFC DEWPOINTS EXTENDING FROM SRN MS NNEWD ACROSS AL INTO FAR SRN MIDDLE TN. A 50 TO 60 KT LOW-LEVEL JET IS LOCATED FROM MIDDLE TN SWD INTO AL. THE LATEST WSR-88D VWP OUT OF BIRMINGHAM AL IS SAMPLING THE LOW-LEVEL SHEAR WELL WITH AN IMPRESSIVE CURVED HODOGRAPH AND 0-1 KM SHEAR ABOVE 30 KT. EVEN THOUGH SBCAPE VALUES ARE RELATIVELY WEAK...THE STRONG DEEP LAYER SHEAR AND IDEAL LOW-LEVEL SHEAR SHOULD CONTINUE TO BE FAVORABLE FOR SUPERCELLS EMBEDDED IN THE LINE WITH TORNADOES. THE STRONG FLOW SHOULD ALSO BE FAVORABLE FOR WIND DAMAGE WITH THE BETTER ORGANIZED BOWING SEGMENTS WITHIN THE LINE.

Mesoscale Discussion #0155


CONCERNING...OUTLOOK UPGRADE 

   

VALID 051547Z - 051715Z

   

THE HIGH RISK IS CURRENTLY BEING EXPANDED NEWD TO INCLUDE ALL OF NERN AR...SERN MO...FAR SRN IL...WRN KY AND WRN TN.

   

LOW LEVEL MOISTENING WILL PERSIST OVER BROAD WARM SECTOR WITH WIND SHEAR BECOMING EXTREME LATE THIS AFTERNOON INTO THIS EVENING. SUPERCELLS AND BOW STRUCTURES ARE EXPECTED TO FORM NEAR THE SURFACE LOW...TRACKING NEWD WITH TIME ALONG WARM FRONT. TORNADOES AND PARTICULARLY DAMAGING WIND GUSTS WILL BE POSSIBLE.

   

FOR MORE INFORMATION...PLEASE SEE UPCOMING 1630Z DAY 1 CONVECTIVE OUTLOOK.

   

NOTE: THE ORIGINAL HIGH RISK AREA ALSO REMAINS IN EFFECT...INCLUDING MUCH OF CNTRL AND SRN AR AS WELL AS NWRN MS.

Mesoscale Discussion #0158


CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   

VALID 051811Z - 051945Z

   

CONDITIONS ARE BECOMING INCREASINGLY FAVORABLE FOR SEVERE STORMS WITH TORNADOES TO DEVELOP...AND A WATCH MAY BE REQUIRED WITHIN THE NEXT COUPLE OF HOURS.

   

TEMPERATURES HAVE RISEN INTO THE MID 70S OVER MUCH OF THE WARM SECTOR WITH 63-66 F DEWPOINTS COMMON. SOME CAPPING REMAINS ESPECIALLY WITH SWD EXTENT BUT CONTINUED HEATING AND DEEPENING OF THE MOIST BL WILL ERODE CAP FROM BELOW. 

   

OVERALL...FORCING IS RATHER UNFOCUSED IN THE FREE WARM SECTOR. HOWEVER...DEEPENING LINES OF CU...WITH CONTINUED DESTABILIZATION...MAY RESULT IN A FEW LONGER LIVED UPDRAFTS LEADING TO ISOLATED THUNDERSTORMS. WIND SHEAR PROFILES ARE QUITE FAVORABLE FOR STORM ROTATION...THUS ANY STORMS THAT FORM COULD PRODUCE TORNADOES.

Mesoscale Discussion #0163


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 37 CONTINUES.

   

SUPERCELLS ARE EXHIBITING VERY STRONG COUPLETS AND ARE PRODUCING TORNADOES ACROSS NRN MS AND WRN TN. THIS CLUSTER OUTBREAK OF TORNADOES WILL LIKELY PERSIST FOR SEVERAL HOURS. 

   

AREA WIND PROFILERS ARE SHOWING IN EXCESS OF 300-500 M2/S2 0-1 SRH. GIVEN STEEP MID TO UPPER LEVEL LAPSE RATES IN PLACE AND TREMENDOUS SHEAR...A FEW OF THESE TORNADOES MAY BECOME VIOLENT...PRODUCING DAMAGE OVER LONG SWATHS AND ENDANGERING LIVES.

Mesoscale Discussion #0165


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 35...36...37...CONTINUES.

   

WARM SECTOR ENVIRONMENT IS CHARACTERIZED BY A DEEP...NEAR SATURATED MOIST LAYER WEAKLY CAPPED BY A ELEVATED MIXED LAYER...CONTRIBUTING TO CAPE ON THE ORDER OF 1000-1500 J/KG.  AND...THIS CONTINUES TO SUPPORT VIGOROUS DISCRETE CONVECTIVE DEVELOPMENT AHEAD OF PRE-FRONTAL SQUALL LINE...WITHIN THE PRESENCE OF STRONG DEEP LAYER SHEAR AND LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS...FAVORABLE FOR LONG LIVED SUPERCELLS WITH STRONG TORNADOES.  THOUGH THE BOUNDARY LAYER MAY COOL A COUPLE OF DEGREES OVER THE NEXT FEW HOURS...LARGE-SCALE FORCING ASSOCIATED WITH VIGOROUS UPSTREAM SHORT WAVE IMPULSE PROBABLY WILL CONTINUE TO SUPPORT DISCRETE SUPERCELLS AHEAD OF SQUALL LINE INTO THE EVENING HOURS.

   

SOUTHWESTERLY MID TROPOSPHERIC JET EAST OF UPPER IMPULSE IS PROGGED TO STRENGTHEN IN EXCESS OF 100 KT ACROSS THE ARKLATEX THIS EVENING.  AND...THE DRY MID-LEVEL AIR MASS MAY CONTRIBUTE TO SUFFICIENT EVAPORATIVE COOLING AND DOWNWARD TRANSPORT OF HIGHER MOMENTUM AIR TO THE SURFACE...POSSIBLY SUPPORTING A NORTHEASTWARD ACCELERATION OF THE SQUALL LINE AND AN INCREASING DAMAGING WIND THREAT THROUGH 02-03Z.  

   

THE RISK FOR LARGE HAIL WILL ALSO EXIST WITH MOST CONVECTION.

Mesoscale Discussion #0170


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 39 CONTINUES.

   

ADDITIONAL WWS MAY BE NEEDED EASTWARD ACROSS THE UPPER OHIO VALLEY TONIGHT.

   

AGEOSTROPHIC FORCING...IN THE RIGHT ENTRANCE REGION OF STRONG HIGH LEVEL JET ACROSS THE UPPER GREAT LAKES REGION INTO THE ST. LAWRENCE VALLEY...WILL CONTINUE TO SUPPORT THE EASTWARD PROGRESSION OF THE LARGE CONVECTIVE CLUSTER THROUGH THE LOWER OHIO VALLEY INTO THE OVERNIGHT HOURS.  INTENSE LEADING EDGE OF ACTIVITY IS ADVANCING AHEAD OF MAIN FRONTAL WAVE...ON THE NOSE OF A STRENGTHENING /60-70 KT/ SOUTHERLY LOW-LEVEL JET CORE...WHICH IS PROGGED TO SHIFT NORTHEAST OF WESTERN TENNESSEE INTO NORTH CENTRAL KENTUCKY BETWEEN 03-06Z.  THIS WILL CONTRIBUTE TO CONTINUING DAMAGING WIND POTENTIAL WITH THE SQUALL LINE AS IT PROGRESSES ACROSS THE LOUISVILLE AND CINCINNATI METROPOLITAN AREAS.  

   

EXTREME LOW-LEVEL SHEAR MAY SUPPORT TORNADOES WITHIN LINE...BUT THE CLUSTER OF MORE DISCRETE SUPERCELLS BENEATH DIFLUENT UPPER REGIME...EAST NORTHEAST OF THE LOW-LEVEL JET CORE...APPEARS LIKELY TO SHIFT NORTHEAST OF BOWLING GREEN INTO THE FRANKFORT/LEXINGTON AREAS.  AND...CONTINUED WARMING/MOISTENING OF THE BOUNDARY LAYER ACROSS SOUTH CENTRAL KENTUCKY INTO THE BLUE GRASS IS EXPECTED TO MAINTAIN A RISK FOR TORNADOES...IN FAVORABLY SHEARED ENVIRONMENT.

Mesoscale Discussion #0171


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 40 CONTINUES.

   

AN ADDITIONAL WW PROBABLY WILL BE NEEDED SOUTH OF CURRENT WW SOON.

   

FORCING SUPPORTING ONGOING CLUSTER OF TORNADIC SUPERCELLS...NEAR/NORTHWEST OF NASHVILLE...IS EXPECTED TO DEVELOP NORTHEAST OF MIDDLE TENNESSEE BY 04-05Z.  BUT...SEVERE THREAT WILL PERSIST UNTIL UPSTREAM SQUALL LINE ADVANCES THROUGH THE INTERSTATE 65 CORRIDOR DURING THE 06-08Z TIME FRAME.  THE RISK FOR DAMAGING WINDS MAY BE THE PRIMARY SEVERE THREAT WITH THE SQUALL LINE...BUT LOW-LEVEL SHEAR WILL REMAIN VERY STRONG AND SUPPORTIVE OF CONTINUING TORNADO POTENTIAL...AS THE BOUNDARY LAYER REMAINS RELATIVELY WARM/ MOIST AND POTENTIALLY BUOYANT.

Mesoscale Discussion #0419


CONCERNING...OUTLOOK UPGRADE 

   

VALID 151530Z - 151630Z

   

INCREASING PROBABILITIES OF TORNADOES FOR LATE AFTERNOON/EARLY EVENING -- REPRESENTING EWD SHIFT OF THREAT INDICATED EARLIER ACROSS GA/SC -- WILL DRIVE CATEGORICAL SPC DAY-1 OUTLOOK UPGRADE TO MDT RISK EWD TO COAST.  REF UPCOMING 1630Z FCST FOR MORE DETAILS.

Mesoscale Discussion #0422


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 119 CONTINUES.

   

AS ADJOINING WARM SECTOR CONTINUES TO HEAT/DESTABILIZE GRADUALLY...CONVECTION IS BUILDING AND BECOMING SVR INVOF AL/GA STATE LINE...ALONG WRN SEGMENT OF COMBINED SFC WARM FRONT AND OUTFLOW BOUNDARY.  SFC WINDS IN WARM SECTOR HAVE VEERED IN RESPONSE TO EWD SHIFT OF STRONGEST ISALLOBARIC FORCING ASSOCIATED WITH NERN GA TORNADIC STORM...AND ASSOCIATED MESOCIRCULATION.  HOWEVER...BULK SHEAR ACROSS N-CENTRAL/NWRN GA WILL REMAIN FAVORABLE -- E.G. ROUGHLY 60 KT EFFECTIVE SHEAR MAGNITUDE FROM FFC RAOB AND RUC SOUNDINGS...AND 0-1 KM SRH STILL EXCEEDING 200 J/KG BASED ON VWP AND RAOB DATA.  MODIFIED 18Z FFC RAOB INDICATES THAT SFC TEMPS LOW-MID 70S F AND DEW POINTS LOW 60S SUPPORT MLCAPES 1000-1500 J/KG AND VERY WEAK CINH.  STRENGTHENING SUPERCELLS OVER CALHOUN/CLEBURNE COUNTIES AL AT 19Z ARE MOVING ENE 40-45 KT.  ASSOCIATED RISK OF DAMAGING HAIL/WIND AND POSSIBLY TORNADOES COULD AFFECT ATL METRO AREA DURING 20-21Z TIME FRAME THEN ENEWD TOWARD AREAS NEAR AND JUST N AHN IN ENSUING 1-2 HOURS.

Mesoscale Discussion #0773


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 249...250...CONTINUES.

   

ADDITIONAL WWS MAY BE NEEDED EAST/SOUTHEAST OF WW 249.  BUT...THE PRIMARY TORNADO THREAT WITH POTENTIALLY LONG-LIVED SUPERCELLS MAY SHIFT INTO PARTS OF WESTERN KENTUCKY/TENNESSEE BY 19-20Z.

   

SEVERAL DISCRETE...POTENTIALLY TORNADIC SUPERCELLS ARE NOW ONGOING NEAR/JUST AHEAD OF PRE-FRONTAL LOW-LEVEL CONFLUENT ZONE NOW BISECTING ARKANSAS IN NORTHEAST/SOUTHWEST FASHION.  THIS IS ALONG/JUST WEST OF A 50-60 KT SOUTHERLY 850 JET AXIS...WHICH IS PROGGED TO CONTINUE TO GRADUALLY SHIFT NORTHEASTWARD THROUGH THE AFTERNOON HOURS...AS A 90 KT 500 MB SPEED MAXIMUM NOSES NORTHEAST OF THE MISSOURI OZARKS.  BY 19-20Z...STRONGEST LOW-LEVEL SHEAR/ LARGEST LOW-LEVEL HODOGRAPHS ARE EXPECTED TO BE CONCENTRATED NEAR THE LOW-LEVEL JET CORE EXTENDING ACROSS WESTERN TENNESSEE/KENTUCKY INTO EXTREME SOUTHERN ILLINOIS/INDIANA.  ADVECTION OF MID/UPPER 60S SURFACE DEW POINTS INTO THIS REGION BY THAT TIME IS EXPECTED TO CONTRIBUTE TO A FAVORABLE BOUNDARY LAYER ENVIRONMENT FOR TORNADIC DEVELOPMENT...INCLUDING THE RISK FOR ISOLATED STRONG TORNADOES.

   

FARTHER TO THE SOUTH/WEST...INTO PARTS OF NORTHERN LOUISIANA... WEAKENING LOW-LEVEL SHEAR AND BACKING MID/UPPER FLOW AHEAD OF THE NEXT IMPULSE PIVOTING AROUND THE MID-LEVEL CLOSED LOW...INTO THE SOUTHERN PLAINS...ARE EXPECTED TO CONTRIBUTE TO MORE UNCERTAIN TORNADIC POTENTIAL.  BUT...THE BOUNDARY LAYER ACROSS THE LOWER MISSISSIPPI VALLEY WILL REMAIN VERY MOIST WITH CAPE IN EXCESS OF 2000 J/KG...IN THE PRESENCE OF DEEP LAYER SHEAR WHICH SHOULD REMAIN SUFFICIENT FOR AT LEAST ISOLATED SUPERCELLS.

Mesoscale Discussion #0853


CONCERNING...OUTLOOK UPGRADE 

   

VALID 100905Z - 101100Z

   

A VERY ACTIVE SEVERE WEATHER DAY IS EXPECTED THIS AFTERNOON AND TONIGHT. AN INITIAL /06Z/ MODERATE RISK EXISTS ACROSS MUCH OF THE ARKLATEX/MID SOUTH REGION AND CENTRAL GULF COAST STATES. THIS MODERATE RISK WILL BE EXPANDED NORTH/EASTWARD WITH THE UPCOMING 13Z DAY 1 CONVECTIVE OUTLOOK.

   

ESPECIALLY REGARDING THE NORTH EXTENT...PRIMARY CONCERN IS THE POTENTIAL INTENSIFICATION OF THE MID LEVEL TROUGH LATE TODAY...WITH RAPID DEEPENING OF THE SURFACE LOW FROM EASTERN KS INTO THE MIDDLE MISSISSIPPI VALLEY TONIGHT. EXPECTED EXPANSION OF THE 13Z MODERATE RISK WOULD NOW INCLUDE FAR EASTERN OK/NORTHERN AR/SOUTHERN MO/SOUTHERN IL/WESTERN KY/WESTERN AND MIDDLE TN INTO NORTHERN AL/MUCH OF GA. A PUBLIC SEVERE WEATHER OUTLOOK /PWO/ WILL BE ISSUED SHORTLY.

Mesoscale Discussion #0867


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 293 CONTINUES.

   

UPR TROUGH AND ASSOCD LARGE SCALE ASCENT WAS BEGINNING TO SPREAD EWD INTO ERN OK/KS LATE THIS AFTN WITH A SUBSEQUENT INCREASE IN TSTMS ALONG THE COLD FRONT/DRYLINE FROM ERN KS SWD INTO ERN OK.  LATEST MESOANALYSIS PLACES AN OUTFLOW ENHANCED WARM FRONT FROM N OF CHANUTE KS SEWD INTO NCNTRL AR.  S OF THIS FRONT THE AIR MASS HAS RECOVERED FROM EARLIER ACTIVITY WITH MLCAPES OF 1500-2000 J/KG OWING TO UPR 60S DEW POINTS RIDING NWD BENEATH 7-7.5 DEG C/KM H7-H5 LAPSE RATES. WITH STRONGEST PRESSURE FALLS INTO SCNTRL MO...THE DEVELOPING LOW OVER ECNTRL KS SHOULD MOVE INTO THE MO OZARKS EARLY THIS EVENING WITH SOME RECOVERY OF THE AIR MASS INTO SCNTRL MO.  

   

THROUGH MID-EVENING...EXPECT THAT THE HIGHEST TORNADO THREAT WILL REMAIN ALONG/S OF THE WARM FRONT IN ERN OK...EXTREME SWRN/SCNTRL MO AND NRN AR.  OTHERWISE...ACTIVITY DEVELOPING ALONG THE PRIMARY COLD FRONT AND WITHIN THE WARM ADVECTION REGIME FARTHER E AND N INTO ECNTRL/SERN MO WILL LIKELY GIVE ISOLD LARGE HAIL.  IF THE AIR MASS CAN FULLY RECOVER DOWNSTREAM INTO THE REMAINDER OF SRN MO...ACTIVITY DEVELOPING ALONG THE KS/MO BORDER MAY BEGIN MOVING INTO AREAS JUST E OF THE CURRENT TORNADO WATCH AROUND 01-02Z.

Mesoscale Discussion #0969


CONCERNING...SEVERE POTENTIAL...WATCH NEEDED SOON 

   

VALID 221706Z - 221730Z

   

AIRMASS IS WARMING/DEEPENING RAPIDLY ACROSS MUCH OF CNTRL/SERN CO.  RESULTANT MIXING HAS FORCED DRYLINE NWD ACROSS ELBERT AND LINCOLN COUNTIES.  THUNDERSTORMS HAVE RECENTLY DEVELOPED FROM THE NORTH-WEST OF DENVER AND WILL GRADUALLY SPREAD/INTENSIFY EWD AS BUOYANCY/UPSLOPE INCREASE OVER THE NEXT FEW HOURS.  NEEDLESS TO SAY...SHEAR PROFILES ARE IMPRESSIVE AND WILL SUPPORT SUPERCELLS AND TORNADOES.  NWD STORM MOTIONS WILL RESULT IN SEVERE SPREADING ATOP COOLER ELY FLOW INTO PORTIONS OF SERN WY/NEB PANHANDLE.


**This MCD was published as the Windsor, CO EF3 was ongoing

Mesoscale Discussion #0990


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 341 CONTINUES.

   

LOW LEVEL DIRECTIONAL SHEAR/SRH VALUES INCREASING ACROSS WRN KS AS LOW LEVEL WINDS IN THE WARM SECTOR CONTINUE TO BACK TO SELY...SUPPORTING AN INCREASING THREAT FOR SUSTAINED TORNADIC SUPERCELLS INTO THE EVENING.

   

GREATEST TORNADO POTENTIAL THROUGH 00Z IS EXPECTED TO BE ALONG AND E OF A DRY LINE...OR 35 MILES EITHER SIDE OF A LINE FROM 40 E LBL TO 15 SE MCK.  SATELLITE/RADAR IMAGERY SHOWED HIGH BASED TSTMS SPREADING ENEWD THROUGH ERN CO WHICH INDICATED THE LEADING EDGE OF DEEP LAYER ASCENT ATTENDANT TO A MID LEVEL SHORT WAVE TROUGH.  LOW LEVEL WINDS ACROSS THE WARM SECTOR WILL CONTINUE TO BACK IN RESPONSE TO NEWD MOVING SHORT WAVE TROUGH...AND STRENGTHEN RESULTING IN INCREASING LOW LEVEL HODOGRAPH CURVATURE.  ASCENT WITH THE TROUGH COMBINED WITH STRONG LOW LEVEL CONVERGENCE IN VICINITY OF THE DRY LINE WILL SUPPORT ADDITIONAL TSTM DEVELOPMENT THIS EVENING... BECOMING TORNADIC.  WARM SECTOR AIR MASS REMAINS MODERATELY-VERY UNSTABLE WITH EFFECTIVE BULK SHEAR VALUES EXCEEDING 50 KT AND ORIENTED AT AN ANGLE TO THE DRY LINE...RESULTING IN POTENTIAL FOR ADDITIONAL DISCRETE STORMS.

   

FARTHER NW ACROSS FAR NWRN KS INTO NERN CO...THE HIGH-BASED ACTIVITY LOCATED ACROSS ERN CO IS EXPECTED TO INCREASE IN INTENSITY/SEVERE POTENTIAL AS IT ENCOUNTERS THE AXIS OF GREATER INSTABILITY EXTENDING NWWD FROM KS INTO NERN CO.

Mesoscale Discussion #1028


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 359 CONTINUES.

   

SUPERCELLS HAVE EVOLVED RAPIDLY ACROSS CNTRL MN JUST S OF KSTC AND NE OF KRWF AS THE CAP HAS ERODED AMIDST RAPIDLY WARMING SFC TEMPERATURES.  THESE CELLS WILL LIKELY TRACK EWD NEAR/JUST N OF AN OUTFLOW BOUNDARY DRAPED SEWD INTO THE CNTRL AND NRN PORTIONS OF THE MINNEAPOLIS METROPOLITAN AREA.  N OF THE BOUNDARY...ESELY LOW-LEVEL FLOW WAS SOMEWHAT WEAK...BUT DIRECTIONAL SHEAR WAS GOOD WITH 0-1KM SRH OF 200+ M2/S2.  SOUTH OF THE BOUNDARY...WINDS HAVE VEERED...LESSENING LOW-LEVEL SHEAR.  

   

HIGHEST TORNADO POTENTIAL WILL EXIST NEAR AND N OF THE MINNEAPOLIS METRO AREA INTO ADJACENT PORTIONS OF WCNTRL WI THROUGH 00Z. OTHERWISE...STORMS DEVELOPING THROUGHOUT CNTRL/SERN MN...NRN IA AND SWRN WI WILL BE CAPABLE OF VERY LARGE HAIL AND DMGG WIND GUSTS. TORNADOES WILL BE A THREAT WATCH WIDE.

Mesoscale Discussion #1029


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 363 CONTINUES.

   

STORMS CAPABLE OF PRODUCING LARGE HAIL...DMGG WINDS...AND TORNADOES WILL CONTINUE TO DEVELOP ACROSS IOWA THIS EVENING. 

   

STORM CLUSTER LOCATED IN NERN IOWA NEAR KCCY APPEARS TO HAVE OVERCOME CIN ON 18Z DVN SOUNDING...AS LOW LEVEL ROTATION IS EVIDENT ON RADAR. DESPITE VEERING OF SURFACE WINDS SEEN ON LATEST 2150Z OBSERVATIONS AND STORM INTERFERENCE...THESE STORMS MAY STILL HAVE POTENTIAL TO PRODUCE TORNADOES...ESPECIALLY AS THEY MOVE TOWARDS THE WARM FRONT. SOUTHERN END STORM CURRENTLY LOCATED IN BUTLER COUNTY LIKELY HAS BEST TORNADIC POTENTIAL AS IT DRAWS IN HIGHER THETA-E AIR WITH LITTLE INTERFERENCE FROM STORMS TO THE N. 

   

TO THE W...ADDITIONAL THUNDERSTORMS ARE DEVELOPING BEHIND THIS CLUSTER ALONG WSWLY TO ENELY ORIENTED LINE OF CONVERGENCE. STORMS WILL LIKELY RAPIDLY INTENSIFY OVER THE NEXT HOUR.


**This MCD was published as the Parkersburg, IA EF5 was ongoing

Mesoscale Discussion #1078


CONCERNING...OUTLOOK UPGRADE 

   

VALID 291032Z - 291230Z

   

MUCH OF ERN NEB...WRN IA...AND EXTREME SERN SD WILL BE UPGRADED TO A HIGH RISK AT 13Z TODAY.

   

...PUBLIC SEVERE WEATHER OUTLOOK...

   

A STRONG UPPER TROUGH IS CURRENTLY MOVING ACROSS PARTS OF UTAH/ARIZONA...AND WILL TRACK INTO THE CENTRAL PLAINS BY LATE THIS AFTERNOON.  AHEAD OF THIS SYSTEM...STRONG SOUTHERLY LOW LEVEL WINDS ARE DRAWING A VERY MOIST AND UNSTABLE AIRMASS NORTHWARD INTO THE CENTRAL PLAINS.  THUNDERSTORMS ARE EXPECTED TO DEVELOP AND RAPIDLY BECOME SEVERE OVER PARTS OF CENTRAL NEBRASKA...NORTH CENTRAL KANSAS...AND SOUTH CENTRAL SOUTH DAKOTA BY MID/LATE AFTERNOON. THESE STORMS WILL LIKELY BE SUPERCELLS CAPABLE OF VERY LARGE HAIL...DAMAGING WINDS...AND TORNADOES. ACTIVITY WILL INCREASE IN COVERAGE AND INTENSITY THROUGH THE EVENING AS THUNDERSTORMS SPREAD INTO PARTS OF WESTERN IOWA AND SOUTHWEST MINNESOTA.  THE COMBINATION OF A VERY UNSTABLE AIRMASS AND STRONG VEERING/INCREASING WINDS WITH HEIGHT INDICATE A RISK OF STRONG TORNADOES OVER THE REGION THIS AFTERNOON AND EVENING.

Mesoscale Discussion #1224


CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 051535Z - 051700Z

   

SEVERE THREAT SHOULD INCREASE BY EARLY AFTERNOON...AND A WATCH WILL BE ISSUED SHORTLY.

   

WHILE INCREASING CONVECTIVE DEVELOPMENT IS EXPECTED THROUGH THE MIDDAY HOURS FARTHER NORTH...INHIBITION BENEATH THE NOSE OF A WARM ELEVATED MIXED LAYER WILL BE AN ISSUE IN CLOSER PROXIMITY TO THE WARM FRONT.  THE FRONT IS IN THE PROCESS OF LIFTING NORTHWARD OUT OF KANSAS INTO THE MID MISSOURI VALLEY...EAST NORTHEAST OF A SEASONABLY DEEP AND DEEPENING SURFACE LOW MIGRATING ACROSS NORTHWEST KANSAS INTO SOUTHWEST NEBRASKA.

   

HIGHEST PROBABILITY FOR THE INITIATION OF BOUNDARY LAYER BASED STORMS THROUGH 18-20Z MAY BE WHERE A 60 KT SOUTHERLY 850 MB JET STREAK INTERSECTS FRONT...ACROSS SOUTHEAST NEBRASKA...WEST/SOUTHWEST OF OMAHA.  IN THE PRESENCE OF MODERATE INSTABILITY...WITH MIXED LAYER CAPE INCREASING IN EXCESS OF 2000 J/KG...STRONG DEEP LAYER SHEAR AND LARGE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS...TORNADIC SUPERCELLS SEEM PROBABLE BENEATH BROADER SCALE DIFLUENT UPPER FLOW REGIME.  STRONG TORNADOES ARE POSSIBLE.

Mesoscale Discussion #1228


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 461...462...CONTINUES.

   

CYCLONIC MID-LEVEL JET CONTINUES TO GRADUALLY EDGE EASTWARD THROUGH THE CENTRAL PLAINS.  AND...COOLING/LIFT ALONG/WEST OF THE JET AXIS IS WEAKENING INHIBITION ALONG INITIAL SURFACE COLD FRONT ADVANCING THROUGH THE CENTRAL PLAINS.  CONVECTIVE DEVELOPMENT IS UNDERWAY...AND RAPID INTENSIFICATION/INCREASE IN AREAL COVERAGE IS ANTICIPATED BETWEEN NOW AND 20-21Z.  

   

IN THE PRESENCE OF STEEPENING LAPSE RATES...MIXED LAYER CAPE OF 2000-3000 J/KG...AND STRONG DEEP LAYER SHEAR...A SEVERE SQUALL LINE LIKELY WILL DEVELOP ACROSS CENTRAL KANSAS INTO SOUTH CENTRAL NEBRASKA.  THIS PROBABLY WILL BE ACCOMPANIED BY INCREASING POTENTIAL FOR STRONG TO EXTREMELY DAMAGING STRAIGHT LINE WINDS AS AN 80-90 KT SOUTH SOUTHWESTERLY 500 MB JET CORE REDEVELOPS OUT OF THE SOUTHERN ROCKIES INTO WESTERN/CENTRAL KANSAS.  

   

STRONGER LOW-LEVEL WARM ADVECTION REGIME AND CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS WILL BE FOCUSED ACROSS CENTRAL INTO EASTERN NEBRASKA.  THIS IS WHERE STORMS MAY REMAIN DISCRETE THE LONGEST BEFORE POSSIBLY CONGEALING INTO A LARGER STORM CLUSTER.  SYNOPTIC WARM FRONT NEAR/NORTH OF BROKEN BOW INTO THE SIOUX CITY IA AREA MAY PROVIDE A FOCUS.  BUT...SURFACE FLOW REMAINS BACKED AROUND TO SOUTHEASTERLY...SOUTHWARD INTO THE KANSAS/NEBRASKA BORDER AREA...NORTH OF OLD WARM FRONT/OUTFLOW BOUNDARY.  FAVORABLE HODOGRAPHS COUPLED WITH AMBIENT VERTICAL VORTICITY NEAR DEEP SURFACE CYCLONE...BENEATH BROADER SCALE DIFLUENT UPPER FLOW...MAY CONTRIBUTE TO A FEW LONG LIVED SUPERCELLS WITH STRONG TORNADOES.

Mesoscale Discussion #1232


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 461 CONTINUES.

   

IT APPEARS THAT THE 80-90 KT SOUTH SOUTHWESTERLY 500 MB JET CORE HAS EMERGED FROM THE SOUTHERN ROCKIES.  AND...THIS FEATURE WILL CONTINUE TO NOSE ACROSS THE CENTRAL PLAINS THROUGH THE REMAINDER OF THE AFTERNOON.  FORCING/DESTABILIZATION IN ITS EXIT REGION HAS CONTRIBUTED TO INCREASING CONVECTIVE DEVELOPMENT ALONG INITIAL COOL SURGE INTO CENTRAL NEBRASKA/KANSAS...WITH MORE SCATTERED CELLS FARTHER WEST...AHEAD OF THE NEXT DEEPER COLD SURGE.  

   

TORNADIC POTENTIAL WITH DISCRETE CELL SOUTH/EAST OF NORTH PLATTE COULD INCREASE AS IT ENCOUNTERS MORE FAVORABLE ENVIRONMENT IN THE WARM SECTOR OF THE DEEP SURFACE CYCLONE NORTHEAST OF NORTH PLATTE...THROUGH THE BROKEN BOW AREA...BETWEEN NOW AND 21-22Z. OTHERWISE...TORNADO POTENTIAL SHOULD INCREASE IN THE PEAK AFTERNOON HEATING...WITHIN PRE-FRONTAL STORMS IN ARCING BAND ON LEADING EDGE OF STRONGER MID-LEVEL COOLING...NEAR GRAND ISLAND NORTHWARD THROUGH AREAS NEAR/WEST OF O'NEILL. WITH SURFACE WINDS MAINTAINING A SOUTHEASTERLY COMPONENT...LOW-LEVEL HODOGRAPHS ARE MAXIMIZED ACROSS THIS REGION.  AND...ISOLATED STRONG TORNADOES ARE POSSIBLE. 

   

SUBSTANTIAL CAP MAY CONTINUE TO SUPPRESS DEVELOPMENT FARTHER EAST...UNTIL STRONGER MID-LEVEL COOLING APPROACHES THE MISSOURI RIVER LATER THIS AFTERNOON/EARLY EVENING.

Mesoscale Discussion #1264


CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   

VALID 071850Z - 071945Z

   

NEW WW IS BEING ISSUED.

   

CELLS...INITIATING EARLIER IN FAVORABLE WARM ADVECTION REGIME ACROSS UPPER PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY...ARE INTENSIFYING RAPIDLY NEAR THE IOWA/ILLINOIS BORDER AREA...AS THEY BECOME INCREASINGLY ROOTED IN A MODERATE TO STRONGLY UNSTABLE BOUNDARY LAYER WITH CAPE UP TO 3000 J/KG.  THIS IS OCCURRING NEAR A LOW-LEVEL CONFLUENCE ZONE...PERHAPS ASSOCIATED WITH AN OLD OUTFLOW BOUNDARY...AND ACTIVITY SEEMS LIKELY TO TRACK NORTH NORTHEASTWARD ALONG TOWARD ACROSS EXTREME EASTERN IOWA/NORTHWESTERN ILLINOIS BETWEEN NOW AND 21-22Z.  LOW-LEVEL HODOGRAPHS ARE NOT PARTICULARLY LARGE ACROSS THIS REGION...BUT AS CELLS TEND TO REMAIN DISCRETE IN THE PRESENCE OF STRONG DEEP LAYER SHEAR...THE BOUNDARY LAYER ENVIRONMENT APPEARS SUPPORTIVE OF TORNADIC POTENTIAL.

Mesoscale Discussion #1269


THE SEVERE WEATHER THREAT FOR TORNADO WATCH 480 CONTINUES.

   

SEVERAL SEVERE STORMS PERSIST OVER NRN KS ALONG THE RETREATING BOUNDARY...WITH OTHER STORMS ONGOING OVER WRN IA/ERN NEB ALONG THE COLD FRONT. THE GREATEST TORNADO THREAT WILL BE ALONG AND SOUTH OF THESE STORMS...WHERE STORM RELATIVE INFLOW REMAINS QUITE UNSTABLE AND MOIST. TO THE N OF THE KS STORMS...RADAR SHOWS OUTFLOW SURGING NWD WHICH WILL LIMIT THE TORNADO THREAT OVER SOUTH CENTRAL NEB...ALTHOUGH SLIGHTLY ELEVATED STORMS WITH STRONG WINDS AND HAIL ARE LIKELY. ADDITIONAL STORMS MAY DEVELOP OVER SERN NEB AND SWRN IA...AND THEY WILL HAVE THE POTENTIAL TO PRODUCE TORNADOES AS LOW LEVEL SHEAR REMAINS QUITE FAVORABLE PER AREA PROFILERS.