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May 2, 2012 - 2nd Chase w/ Kelly

Location:

Steele County, MN

Target:

Medford, MN

Tornadoes:

0

Miles:

145


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There was a slight risk for severe storms across southern MN. There was a warm front draped across southern MN but the parameters didnít look all that great so I decided I would work a full day and then if storms fired after work I could just jet south on 35. Right before dinner time I noticed a storm fire on radar near Mankato. I decided I would eat dinner and then if it still looked good after dinner I would go after it. Well sure enough, when I checked radar after dinner it was tornado warned and had a beautiful classic supercell radar signature.

Immediately I grabbed my laptop and jumped in the car with Kelly. I decided we would head down 169 and then cut through Jordan/New Prague which would get us into pretty good position to intercept. Unfortunately there were some traffic issues getting out of Burnsville so after we got through New Prague we had to head east to 35 if we were going to have any chance of getting in front of it. Prior to intercepting the cell in Medford, it appeared to be weakening on radar but when we got to Medford it really started to intensify. I managed to find a nice viewing area across a farm field and was able to witness a beautiful mesocyclone.

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You could see the inflow band make a 360 degree circle and at the front right of this band the rotation was really tightening up. I was quite convinced that it was going to drop a tornado as it continued to intensify. After watching for about 10 minutes it started getting uncomfortably close to us so we headed east.

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Right as we started heading east it got tornado warned but it never really did anything else after that point. We stuck with it for another 40 miles or so before calling it a night. As we drove back through a heavy rain core, all of the sudden the sun appeared so that was pretty neat seeing the sunset through the heavy rain.

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SPC AC 020600 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT WED MAY 02 2012 VALID 021200Z - 031200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM CNTRL NEB INTO CNTRL IA... ...THERE IS A SLGT RISK OF SVR TSTMS FROM NEB AND SD EWD ACROSS LOWER MI AND INTO THE DELMARVA... ...SYNOPSIS... A BROAD BELT OF SWLY FLOW ALOFT WILL EXTEND FROM THE NRN ROCKIES ACROSS THE NRN PLAINS AND UPPER MS VALLEY. ONE LEAD SHORTWAVE WILL EXIST OVER THE UPPER MS VALLEY AT 12Z WED...AND WILL QUICKLY MOVE NEWD ACROSS THE GREAT LAKES AND INTO ONTARIO. BEHIND THIS WAVE...HEIGHT MAY RISE BRIEFLY AHEAD OF THE NEXT SHORTWAVE TROUGH WHICH WILL AFFECT WRN NEB AND THE DAKOTAS BY 00Z. A LOW LEVEL JET WILL ALSO INCREASE DURING THE EVENING OVER THIS REGION...HELPING TO FUEL COMPLEXES OF SEVERE THUNDERSTORMS FROM NEB INTO IA. ANOTHER WEAK SHORTWAVE WILL EXIST FROM OH INTO THE MID ATLANTIC AND WILL ENHANCE STORM CHANCES THERE. AT THE SURFACE...A VERY LARGE AREA OF MOISTURE AND INSTABILITY WILL BE PRESENT ACROSS THE PLAINS AND MIDWEST EWD ACROSS THE OH/TN VALLEYS AND TO THE MID ATLANTIC. AS A RESULT...A VERY ACTIVE CONVECTIVE DAY IS ANTICIPATED. ...NRN IA/SRN MN...SRN WI AND NRN IL AFTERNOON... AN MCS ONGOING THIS EVENING WILL LIKELY LEAVE BEHIND A SLIGHTLY COOLER AIR MASS OVER PORTION OF IA...MN...AND WI...REINFORCING THE SYNOPTIC BOUNDARY. STRONG INSTABILITY AND A SWLY LOW LEVEL JET MAY ALLOW FOR A CONTINUATION OF SOME ACTIVITY EARLY...FROM NRN MO INTO ERN IA AND NRN IL WITH A MARGINAL THREAT OF WIND AND HAIL. DAYTIME HEATING AND PERSISTENT SLY SURFACE FLOW SHOULD ALLOW RAPID DESTABILIZATION ACROSS THE REGION WITH CAPE VALUES ON THE ORDER OF 2000-3000 J/KG. THE LOW LEVEL FLOW WILL NOT BE PARTICULARLY STRONG...YET AS MASS FIELDS ADJUST TO THE NEXT TROUGH...BUT HODOGRAPHS WILL BE LONG AND WILL STRONGLY FAVOR SUPERCELLS WITH VERY LARGE HAIL FROM SERN SD EWD ACROSS NRN IA...PERHAPS SRN MN AND SWRN WI. ...NEB...SERN SD...WRN IA EVENING/OVERNIGHT... VERY STRONG INSTABILITY WILL BUILD OVER CNTRL AND ERN NEB...PRIOR TO STORMS FORMING IN THE STRONG HEATING OVER W CNTRL NEB. CELLS SHOULD QUICKLY BECOME SUPERCELLULAR WITH VERY LARGE HAIL AND DAMAGING WINDS. MODELS ARE IN GOOD AGREEMENT DEPICTING A JETLET...POSSIBLY RELATED TO CONVECTIVE FEEDBACK...MOVING FROM NEB INTO WRN IA. THIS IS LIKELY DUE TO EXPLOSIVE RELEASE OF INSTABILITY WITH STEEP LAPSE RATES AND HIGH PRECIPITABLE WATER CONTENT. THE INITIAL SUPERCELLS WILL LIKELY MERGE DURING THE EVENING...BECOMING AN MCS CAPABLE OF WIDESPREAD DAMAGING WINDS AS FAR E AS WRN IA. ...MD...ERN VA...ERN NC... STRONG HEATING IS EXPECTED ACROSS THE AREA...PERHAPS IN THE WAKE OF REMNANTS FROM THIS EVENINGS STORMS UPSTREAM OVER WV. FORECAST SOUNDINGS INDICATE THAT 1500-2000 J/KG MLCAPE WILL BE PRESENT AND NO CAPPING WILL EXIST. WITH WNWLY FLOW ALOFT...ANY STORMS THAT FORM UPSTREAM WILL HAVE THE POTENTIAL TO GROW UPSCALE INTO AN MCS CAPABLE OF BOTH WIND AND MARGINAL HAIL. ...CNTRL KS/WRN OK/NWRN TX DRYLINE... A HIGHLY CONDITIONAL SEVERE THREAT WILL EXIST BY LATER AFTERNOON ALONG THE DRYLINE. EXTREME INSTABILITY WILL BUILD UP ALONG THE DRYLINE WHERE BOUNDARY LAYER DEWPOINTS WILL RISE INTO THE UPPER 60S F BENEATH STEEP LAPSE RATES ALOFT. FORECAST SOUNDINGS SUGGEST THAT TOTAL MIXING WILL OCCUR W OF THE DRYLINE THROUGH 500 MB...WHILE THE AIR MASS E OF THE DRYLINE REMAINS CAPPED. THUS...A NARROW ZONE OF UNCAPPED AND VERY UNSTABLE AIR WILL EXIST NEAR THE DRYLINE. ..JEWELL/GARNER.. 05/02/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z

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SPC AC 021235 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0735 AM CDT WED MAY 02 2012 VALID 021300Z - 031200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS EVENING AND OVERNIGHT OVER PARTS OF CENTRAL/EASTERN NEB AND WESTERN IA... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NORTHERN PLAINS...EASTWARD ACROSS THE UPPER OH VALLEY INTO THE MID ATLANTIC REGION... MORNING SATELLITE LOOPS SHOW A BAND OF RELATIVELY STRONG WESTERLY MID/UPPER LEVEL FLOW EXTENDING FROM THE GREAT BASIN...ACROSS THE CENTRAL/NORTHERN ROCKIES...INTO THE NORTHERN PLAINS. A COUPLE OF STRONG SHORTWAVE TROUGHS ARE EMBEDDED IN THIS FLOW PATTERN...WHICH WILL MOVE INTO THE PLAINS AND HELP TO INITIATE SEVERE THUNDERSTORM ACTIVITY THIS EVENING. ...NEB/IA/MN/WI... A LARGE MCS HAS AFFECTED PARTS OF IA/IL OVERNIGHT...WITH THE REMNANT OUTFLOW BOUNDARY EXTENDING ACROSS NORTHERN MO INTO EASTERN NEB. THE BOUNDARY IS EXPECTED TO RETREAT NORTHWARD THROUGH THE DAY AND EVENTUALLY BECOME THE FOCUS FOR AFTERNOON/EVENING THUNDERSTORM ACTIVITY. RICH LOW LEVEL MOISTURE SOUTH OF THE BOUNDARY...COUPLED WITH STRONG HEATING AND STEEP LAPSE RATES WILL YIELD AFTERNOON MLCAPE VALUES OF OVER 3000 J/KG THROUGHOUT THIS REGION. SUFFICIENT WESTERLY FLOW ALOFT WILL PROMOTE SUPERCELL STORM STRUCTURES CAPABLE OF VERY LARGE HAIL...DAMAGING WINDS...AND A ISOLATED TORNADOES. ...NEB/SD THIS EVENING... OPERATIONAL AND EXPERIMENTAL MODELS ARE IN GOOD AGREEMENT THAT SCATTERED THUNDERSTORMS WILL INTENSIFY BY EARLY EVENING OVER PARTS OF CENTRAL/WESTERN NEB. THE ACTIVITY MAY BEGIN AS HIGH-BASED CONVECTION IN THE DEEPLY MIXED BL OVER WESTERN NEB...BUT WILL MOVE INTO THE HIGH THETA-E AIR MASS OVER CENTRAL NEB AND RAPIDLY STRENGTHEN. SUPERCELLS CAPABLE OF VERY LARGE HAIL AND ISOLATED TORNADOES WILL BE THE INITIAL THREAT. HOWEVER...IN APPEARS LIKELY THAT STORMS WILL GROW UPSCALE INTO ONE OR MORE BOWING COMPLEXES ACROSS THE MODERATE RISK AREA. IF THIS OCCURS...A MORE WIDESPREAD DAMAGING WIND EVENT APPEARS POSSIBLE. ...CENTRAL GREAT LAKES INTO UPPER OH VALLEY... THE MCS OVER THE UPPER MS VALLEY IS WEAKENING THIS MORNING...BUT THE REMNANT MCV MAY HELP TO INITIATE NEW THUNDERSTORMS BY EARLY AFTERNOON OVER PARTS OF IND/LOWER MI. THESE STORMS WILL SPREAD EAST-SOUTHEASTWARD ALONG/NORTH OF WEAK SURFACE BOUNDARY INTO PARTS OF OH/PA/WV THROUGH THE AFTERNOON WITH LOCALLY DAMAGING WINDS AND HAIL. ...MID ATLANTIC REGION... SCATTERED THUNDERSTORMS ARE EXPECTED TO FORM THIS AFTERNOON OVER PARTS OF PA/WV AND SPREAD SOUTHEASTWARD THROUGH THE DAY. THESE STORMS WILL BE IN AN ENVIRONMENT OF SUFFICIENT NORTHWESTERLY FLOW ALOFT TO PROMOTE ORGANIZED MULTICELL OR OCCASIONAL SUPERCELL STORM STRUCTURES CAPABLE OF LOCALLY DAMAGING WINDS AND HAIL. ..HART/SMITH.. 05/02/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z

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SPC AC 021630 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1130 AM CDT WED MAY 02 2012 VALID 021630Z - 031200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF EASTERN/NORTHEAST NEBRASKA INTO SOUTHEAST SOUTH DAKOTA...EXTREME SOUTHWEST MINNESOTA AND A SMALL PORTION OF NORTHWEST IOWA... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA FROM THE CNTRL HIGH PLAINS EAST ACROSS THE UPPER MIDWEST AND SOUTHEAST TO THE MID ATLANTIC... ...CNTRL PLAINS LATE... MORNING SURFACE/UA ANALYSIS REVEALS DEEP-LAYER FRONTAL ZONE EXTENDING SW TO NE OVER THE CNTRL PLAINS TO A SURFACE LOW PRESSURE CENTER IN SRN ONTARIO. THE FRONT IS EMBEDDED WITHIN A BAND OF MODEST 40-50KT SWLY FLOW AT MID LEVELS AND...AT THE SURFACE...THE FRONT IS INTERSECTED BY AN OUTFLOW BOUNDARY OVER ERN NEB. MID/UPPER LEVEL FLOW OBSERVED ON WATER VAPOR DEPICTS A SHORT WAVE TROUGH MOVING ACROSS MT BUT OTHERWISE CAN BE DESCRIBED AS NON-DESCRIPT WITH REGARD TO MORE PROMINENT SHORT WAVE FEATURES THAT MAY AID ASCENT ACROSS THE PLAINS TODAY. IN FACT...MOST GUIDANCE INDICATES WEAK MID LEVEL HEIGHT RISES WILL OCCUR ACROSS MUCH OF THE REGION THROUGH THE DAYLIGHT HOURS. IN ADDITION...SUBSTANTIAL CAPPING ACROSS THE GREAT PLAINS...ESPECIALLY SOUTH OF THE FRONT/OUTFLOW INTERSECTION...WILL LIKELY LIMIT STORM INITIATION AND SUBSEQUENT SEVERE THREAT ACROSS THE MDT RISK AREA UNTIL THIS EVENING. WHILE ENVIRONMENT IS CURRENTLY HOSTILE TO MORE ROBUST TSTM DEVELOPMENT...THAT DOES NOT MEAN THAT A TREMENDOUS AMOUNT OF INSTABILITY CANNOT DEVELOP. IT SEEMS REASONABLE TO EXPECT SBCAPE TO CLIMB TO AROUND 5000 J/KG LATER THIS AFTERNOON BASED ON MORNING SOUNDINGS AND FORECAST HIGH TEMPERATURES IN AREAS EXPERIENCING MAXIMUM HEATING. IT IS POSSIBLE THAT PERSISTENT MESOSCALE CONVERGENCE/LIFT NEAR THE FRONT AND ALONG AND NORTH OF OUTFLOW...FROM ERN NEB ACROSS IA...COULD RESULT IN TSTM DEVELOPMENT IN THESE AREAS BY LATER AFTERNOON. ANY STORMS THAT CAN BREAK THE CAP IN THESE AREAS WILL POSE A THREAT OF LARGE HAIL AND DAMAGING WINDS...AND PERHAPS EVEN A TORNADO...GIVEN THE MAGNITUDE OF INSTABILITY AND EFFECTIVE SHEAR ON THE ORDER OF 40-50KT. WHILE SOME GUIDANCE DOES FORECAST THIS POTENTIAL NEAR THE IA/MN/WI BORDERS BY LATE AFTERNOON...OTHER GUIDANCE DOES NOT. THUS...RELATIVELY HIGH UNCERTAINTY EXISTS IN THIS SCENARIO. MORE CONFIDENCE EXISTS THAT STORMS WILL INITIATE OVER THE CNTRL HIGH PLAINS LATE TODAY THROUGH A COMBINATION OF DIABATIC INFLUENCES AND GREATER LARGE SCALE SUPPORT WITH THE UPPER TROUGH APPROACHING FROM MT. THE ACTIVITY WILL TRACK EAST INTO THE INSTABILITY AXIS FROM NRN KS INTO NEB THIS EVENING AND SHOULD INTENSIFY AND EXPAND INTO ONE OR TWO FORWARD-PROPAGATING STORM COMPLEXES. VERY LARGE HAIL POTENTIAL WILL EXIST WITH EARLY DEVELOPMENT. INCREASE IN NOCTURNAL LOW LEVEL JET SHOULD FURTHER SUSTAIN MASS INFLOW AND KINEMATIC REGIME APPEARS SUPPORTIVE OF WIDESPREAD SEVERE WIND GUSTS SPREADING EAST ACROSS NEB/SERN SD AND PARTS OF SWRN MN AND WRN IA THROUGH LATE TONIGHT. ...UPPER MIDWEST/NRN IA ACROSS WI/NRN IL... FORECAST UNCERTAINTY ALREADY MENTIONED FOR STORMS ACROSS SOME OF THIS AREA LATER THIS AFTERNOON. A MORE LIKELY SCENARIO WOULD BE STORMS INCREASING ALONG/NORTH OF THE RETREATING OUTFLOW/WARM FRONT LATER THIS EVENING AHEAD OF THE BOWING/MCS COMPLEX FARTHER WEST. LARGE HAIL WOULD BE A THREAT WITH THIS DEVELOPMENT GIVEN MAGNITUDE OF UPSTREAM INSTABILITY. VERY HEAVY RAIN POTENTIAL WILL ALSO EXIST ACROSS SOME OF THE AREA GIVEN THE POSSIBILITY OF BACKBUILDING/TRAINING CONVECTION. ...SERN MI ACROSS OH/WRN PA... WATER VAPOR IMAGERY REFLECTS A LOW AMPLITUDE MID-LEVEL TROUGH PROGRESSING EASTWARD OVER LOWER MI/LAKE HURON VICINITY EARLY THIS AFTERNOON. ON THE SOUTHERN PERIPHERY OF THIS FEATURE...IT SEEMS LIKELY THAT TSTMS WILL INCREASE THIS AFTERNOON WITHIN AN INCREASINGLY WARM/UNSTABLE AIRMASS ALONG/SOUTH OF A WARM FRONT ACROSS THE REGION...WITH 2000-3000 J/KG MLCAPE LIKELY WITHIN THE WARM SECTOR. GIVEN THE DEGREE OF INSTABILITY...AND THAT THE REGION/WARM FRONTAL ZONE COINCIDES WITH THE SOUTHERN FRINGE OF MODERATELY STRONG MID-LEVEL WESTERLIES...SUFFICIENT VERTICAL SHEAR /25-35 KT/ WILL EXIST FOR SUSTAINED MULTICELLS/PERHAPS SOME SUPERCELLS. SEVERE HAIL/PERHAPS A BRIEF TORNADO WILL BE POSSIBLE...BUT MORE SO...STORMS SHOULD TEND TO CONGEAL/ORGANIZE AND MOVE EAST-SOUTHEASTWARD WITH A DAMAGING WIND THREAT INTO THIS EVENING. ...MID ATLANTIC... STRONG HEATING/DESTABILIZATION WILL OCCUR THIS AFTERNOON ALONG/SOUTHWEST OF A NEARLY STALLED FRONTAL ZONE FROM WV ACROSS NRN VA TO TIDEWATER...WITH THE MOST AGGRESSIVE DESTABILIZATION LIKELY TO OCCUR NEAR THE APPALACHIANS INTO SOUTHERN/WESTERN VA AND MUCH OF NC. THE STRONGEST WEST-NORTHWESTERLY FLOW ALOFT/VERTICAL SHEAR WILL BE RELATED TO NEAR THE AFOREMENTIONED FRONTAL ZONE...BUT THE DEGREE OF LAPSE RATES/DESTABILIZATION WILL AT LEAST SUPPORT AN ISOLATED/EPISODIC POTENTIAL FOR SEVERE WIND/HAIL THIS AFTERNOON/EARLY EVENING. ...MS DELTA... WEAK AND SLOW MOVING UPPER IMPULSE/MCV WILL AID IN TSTM DEVELOPMENT FROM THE DELTA INTO CNTRL MS AND SRN AL THROUGH THE AFTERNOON. WHILE FLOW IS WEAK...VERY WARM AND MOIST AIRMASS WILL BOOST INSTABILITY SO THAT A FEW STORMS IN THE FORM OF MULTICELLULAR CLUSTERS COULD POSE A THREAT OF SOME HAIL AND DAMAGING WET MICROBURSTS. ..CARBIN/MOSIER/GUYER.. 05/02/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z

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SPC AC 021958 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0258 PM CDT WED MAY 02 2012 VALID 022000Z - 031200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS EVE ACROSS PARTS OF CNTRL/ERN NEBRASKA...SOUTHEASTERN SOUTH DAKOTA...SOUTHWESTERN MINNESOTA...WESTERN IOWA... ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS PARTS OF THE NORTH CENTRAL PLAINS EASTWARD THROUGH THE SOUTHERN GREAT LAKES/OH VALLEY REGION...INTO PARTS OF THE MID ATLANTIC... ...20Z OUTLOOK UPDATE... WEAK MID-LEVEL HEIGHT RISES ARE ONGOING ACROSS MUCH OF THE PLAINS INTO THE GREAT LAKES REGION AND MID ATLANTIC COAST. AND MID/UPPER FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH THE SIGNIFICANT SHORT WAVE IMPULSE LIFTING THROUGH THE NORTHERN ROCKIES WILL LIKELY SPREAD INTO THE SOUTH CENTRAL CANADIAN PROVINCES...WELL NORTH OF THE MID MISSOURI VALLEY...AS LARGE-SCALE UPPER TROUGHING AMPLIFIES OFF THE PACIFIC COAST. UNCERTAINTIES REMAIN CONCERNING CONVECTIVE POTENTIAL ON THE NORTHERN PERIPHERY OF BROADER SCALE SUBTROPICAL RIDGING GRADUALLY BECOMING MORE PROMINENT FROM PORTIONS OF THE SOUTHEASTERN PLAINS INTO THE MID ATLANTIC SEABOARD. HOWEVER...MODESTLY STRONG DEEP LAYER WESTERLY MEAN FLOW FIELDS AND SHEAR REMAIN CONDUCIVE TO THE EVOLUTION OF ORGANIZED STORM CLUSTERS...FROM THE NORTH CENTRAL PLAINS THROUGH THE SOUTHERN GREAT LAKES REGION INTO PARTS OF THE MID ATLANTIC STATES...AS THE BOUNDARY LAYER DESTABILIZES. ...NORTH CENTRAL PLAINS INTO UPPER MIDWEST... THE MOST PROMINENT SURFACE FEATURE REMAINS A RESIDUAL CONVECTIVE OUTFLOW BOUNDARY...EXTENDING FROM REMNANTS OF AN OVERNIGHT CONVECTIVE COMPLEX...NOW CENTERED OVER NORTH CENTRAL ILLINOIS... WEST NORTHWARD INTO THE VICINITY OF THE MID MISSOURI VALLEY. LOW-LEVEL CONVERGENCE IS WEAK...BOTH ALONG THIS BOUNDARY...AND ALONG A WEAK SURFACE TROUGH EXTENDING FROM WESTERN KANSAS INTO CENTRAL NEBRASKA. BUT OBJECTIVE ANALYSIS INDICATES THAT MIXED LAYER CAPE IS BECOMING MODERATELY LARGE ACROSS THIS REGION...AS INSOLATION CONTINUES BENEATH STEEP MID-LEVEL LAPSE RATES. AND A SIGNIFICANT SIGNAL PERSISTS IN MODEL GUIDANCE SUGGESTING A RAPID STRENGTHENING IN LOWER/MID TROPOSPHERIC WARM ADVECTION ACROSS CENTRAL NEBRASKA INTO THE MID MISSOURI VALLEY BY 03-06Z. BASED LARGELY ON THESE TWO POINTS...IT STILL APPEARS THAT POTENTIAL EXISTS FOR THE EVOLUTION OF A SIGNIFICANT MESOSCALE CONVECTIVE SYSTEM BY LATE THIS EVENING...IF NOT BEFORE. THIS ACTIVITY COULD FORWARD PROPAGATE AS FAR EAST AS PORTIONS OF THE UPPER MISSISSIPPI VALLEY BY 12Z THURSDAY...ACCOMPANIED BY CONTINUING POTENTIAL FOR DAMAGING WINDS AND HAIL. ...SOUTHERN GREAT LAKES... SOME CHANGES TO PROBABILITY/CATEGORICAL LINES HAVE BEEN MADE TO ACCOUNT FOR ONGOING TRENDS IN CONVECTION/DESTABILIZATION. THIS INCLUDES A SLIGHT SOUTHWARD ADJUSTMENT OF SLIGHT RISK PROBABILITIES ACROSS PORTIONS OF WEST CENTRAL OHIO AND CENTRAL INDIANA...TO ACCOUNT FOR POSSIBLE CONTINUED INTENSIFICATION OF CONVECTION NOW DEEPENING ALONG OUTFLOW BOUNDARY UPSTREAM. ..KERR.. 05/02/2012 .PREV DISCUSSION... /ISSUED 1130 AM CDT WED MAY 02 2012/ ...CNTRL PLAINS LATE... MORNING SURFACE/UA ANALYSIS REVEALS DEEP-LAYER FRONTAL ZONE EXTENDING SW TO NE OVER THE CNTRL PLAINS TO A SURFACE LOW PRESSURE CENTER IN SRN ONTARIO. THE FRONT IS EMBEDDED WITHIN A BAND OF MODEST 40-50KT SWLY FLOW AT MID LEVELS AND...AT THE SURFACE...THE FRONT IS INTERSECTED BY AN OUTFLOW BOUNDARY OVER ERN NEB. MID/UPPER LEVEL FLOW OBSERVED ON WATER VAPOR DEPICTS A SHORT WAVE TROUGH MOVING ACROSS MT BUT OTHERWISE CAN BE DESCRIBED AS NON-DESCRIPT WITH REGARD TO MORE PROMINENT SHORT WAVE FEATURES THAT MAY AID ASCENT ACROSS THE PLAINS TODAY. IN FACT...MOST GUIDANCE INDICATES WEAK MID LEVEL HEIGHT RISES WILL OCCUR ACROSS MUCH OF THE REGION THROUGH THE DAYLIGHT HOURS. IN ADDITION...SUBSTANTIAL CAPPING ACROSS THE GREAT PLAINS...ESPECIALLY SOUTH OF THE FRONT/OUTFLOW INTERSECTION...WILL LIKELY LIMIT STORM INITIATION AND SUBSEQUENT SEVERE THREAT ACROSS THE MDT RISK AREA UNTIL THIS EVENING. WHILE ENVIRONMENT IS CURRENTLY HOSTILE TO MORE ROBUST TSTM DEVELOPMENT...THAT DOES NOT MEAN THAT A TREMENDOUS AMOUNT OF INSTABILITY CANNOT DEVELOP. IT SEEMS REASONABLE TO EXPECT SBCAPE TO CLIMB TO AROUND 5000 J/KG LATER THIS AFTERNOON BASED ON MORNING SOUNDINGS AND FORECAST HIGH TEMPERATURES IN AREAS EXPERIENCING MAXIMUM HEATING. IT IS POSSIBLE THAT PERSISTENT MESOSCALE CONVERGENCE/LIFT NEAR THE FRONT AND ALONG AND NORTH OF OUTFLOW...FROM ERN NEB ACROSS IA...COULD RESULT IN TSTM DEVELOPMENT IN THESE AREAS BY LATER AFTERNOON. ANY STORMS THAT CAN BREAK THE CAP IN THESE AREAS WILL POSE A THREAT OF LARGE HAIL AND DAMAGING WINDS...AND PERHAPS EVEN A TORNADO...GIVEN THE MAGNITUDE OF INSTABILITY AND EFFECTIVE SHEAR ON THE ORDER OF 40-50KT. WHILE SOME GUIDANCE DOES FORECAST THIS POTENTIAL NEAR THE IA/MN/WI BORDERS BY LATE AFTERNOON...OTHER GUIDANCE DOES NOT. THUS...RELATIVELY HIGH UNCERTAINTY EXISTS IN THIS SCENARIO. MORE CONFIDENCE EXISTS THAT STORMS WILL INITIATE OVER THE CNTRL HIGH PLAINS LATE TODAY THROUGH A COMBINATION OF DIABATIC INFLUENCES AND GREATER LARGE SCALE SUPPORT WITH THE UPPER TROUGH APPROACHING FROM MT. THE ACTIVITY WILL TRACK EAST INTO THE INSTABILITY AXIS FROM NRN KS INTO NEB THIS EVENING AND SHOULD INTENSIFY AND EXPAND INTO ONE OR TWO FORWARD-PROPAGATING STORM COMPLEXES. VERY LARGE HAIL POTENTIAL WILL EXIST WITH EARLY DEVELOPMENT. INCREASE IN NOCTURNAL LOW LEVEL JET SHOULD FURTHER SUSTAIN MASS INFLOW AND KINEMATIC REGIME APPEARS SUPPORTIVE OF WIDESPREAD SEVERE WIND GUSTS SPREADING EAST ACROSS NEB/SERN SD AND PARTS OF SWRN MN AND WRN IA THROUGH LATE TONIGHT. ...UPPER MIDWEST/NRN IA ACROSS WI/NRN IL... FORECAST UNCERTAINTY ALREADY MENTIONED FOR STORMS ACROSS SOME OF THIS AREA LATER THIS AFTERNOON. A MORE LIKELY SCENARIO WOULD BE STORMS INCREASING ALONG/NORTH OF THE RETREATING OUTFLOW/WARM FRONT LATER THIS EVENING AHEAD OF THE BOWING/MCS COMPLEX FARTHER WEST. LARGE HAIL WOULD BE A THREAT WITH THIS DEVELOPMENT GIVEN MAGNITUDE OF UPSTREAM INSTABILITY. VERY HEAVY RAIN POTENTIAL WILL ALSO EXIST ACROSS SOME OF THE AREA GIVEN THE POSSIBILITY OF BACKBUILDING/TRAINING CONVECTION. ...SERN MI ACROSS OH/WRN PA... WATER VAPOR IMAGERY REFLECTS A LOW AMPLITUDE MID-LEVEL TROUGH PROGRESSING EASTWARD OVER LOWER MI/LAKE HURON VICINITY EARLY THIS AFTERNOON. ON THE SOUTHERN PERIPHERY OF THIS FEATURE...IT SEEMS LIKELY THAT TSTMS WILL INCREASE THIS AFTERNOON WITHIN AN INCREASINGLY WARM/UNSTABLE AIRMASS ALONG/SOUTH OF A WARM FRONT ACROSS THE REGION...WITH 2000-3000 J/KG MLCAPE LIKELY WITHIN THE WARM SECTOR. GIVEN THE DEGREE OF INSTABILITY...AND THAT THE REGION/WARM FRONTAL ZONE COINCIDES WITH THE SOUTHERN FRINGE OF MODERATELY STRONG MID-LEVEL WESTERLIES...SUFFICIENT VERTICAL SHEAR /25-35 KT/ WILL EXIST FOR SUSTAINED MULTICELLS/PERHAPS SOME SUPERCELLS. SEVERE HAIL/PERHAPS A BRIEF TORNADO WILL BE POSSIBLE...BUT MORE SO...STORMS SHOULD TEND TO CONGEAL/ORGANIZE AND MOVE EAST-SOUTHEASTWARD WITH A DAMAGING WIND THREAT INTO THIS EVENING. ...MID ATLANTIC... STRONG HEATING/DESTABILIZATION WILL OCCUR THIS AFTERNOON ALONG/SOUTHWEST OF A NEARLY STALLED FRONTAL ZONE FROM WV ACROSS NRN VA TO TIDEWATER...WITH THE MOST AGGRESSIVE DESTABILIZATION LIKELY TO OCCUR NEAR THE APPALACHIANS INTO SOUTHERN/WESTERN VA AND MUCH OF NC. THE STRONGEST WEST-NORTHWESTERLY FLOW ALOFT/VERTICAL SHEAR WILL BE RELATED TO NEAR THE AFOREMENTIONED FRONTAL ZONE...BUT THE DEGREE OF LAPSE RATES/DESTABILIZATION WILL AT LEAST SUPPORT AN ISOLATED/EPISODIC POTENTIAL FOR SEVERE WIND/HAIL THIS AFTERNOON/EARLY EVENING. ...MS DELTA... WEAK AND SLOW MOVING UPPER IMPULSE/MCV WILL AID IN TSTM DEVELOPMENT FROM THE DELTA INTO CNTRL MS AND SRN AL THROUGH THE AFTERNOON. WHILE FLOW IS WEAK...VERY WARM AND MOIST AIRMASS WILL BOOST INSTABILITY SO THAT A FEW STORMS IN THE FORM OF MULTICELLULAR CLUSTERS COULD POSE A THREAT OF SOME HAIL AND DAMAGING WET MICROBURSTS. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z

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MESOSCALE DISCUSSION 0663 NWS STORM PREDICTION CENTER NORMAN OK 0334 PM CDT WED MAY 02 2012 AREAS AFFECTED...NE...SD...MN...IA CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 022034Z - 022200Z PROBABILITY OF WATCH ISSUANCE...60 PERCENT SUMMARY...TSTM DEVELOPMENT APPEARS POSSIBLE OVER THE NEXT FEW HOURS FROM PORTIONS OF NERN NEB ACROSS SERN SD TO SRN MN AND NWRN IA. IF THIS POTENTIAL BECOMES INCREASINGLY LIKELY...A WATCH IS POSSIBLE. DISCUSSION...VERY UNSTABLE CONDITIONS HAVE DEVELOPED IN THE VICINITY OF NUMEROUS AND SUBTLE SMALL SCALE BOUNDARIES FROM THE MIDDLE MISSOURI RIVER VALLEY INTO THE UPPER MS VALLEY THIS AFTERNOON. RESIDUAL OUTFLOW BOUNDARY APPEARS TO HAVE MERGED WITH WEAK SURFACE INVERTED TROUGH AXIS OVER NERN NEB WHERE RECENT SATL IMAGERY WAS SHOWING CU CONGESTUS INCREASING. THE CU ALSO CONTINUE TO BUILD ALONG NERN SEGMENT OF THIS TROUGH AXIS INTO PORTIONS OF SCNTRL MN. IT ALSO APPEARS THAT A WARM FRONT IS BEGINNING TO TAKE FORM ACROSS SRN MN WHERE AIRMASS CONTINUES TO DESTABILIZE AND CONVECTIVE INHIBITION HAS LIKELY WEAKENED. THE ENTIRE REGION LIES BENEATH A BELT OF ANTICYCLONICALLY CURVED SWLY MID LEVEL FLOW AROUND 50KT THAT IS SUPPORTING EFFECTIVE VERTICAL SHEAR ON THE ORDER OF 45-55KT. WHILE LATEST CALIBRATED ENSEMBLE GUIDANCE INDICATES A HIGH PROBABILITY OF SEVERE STORMS TO FORM OVER THE NEXT FEW HOURS IN THIS GENERAL AREA...DETAILS OF INITIATION AND SUBSEQUENT STORM EVOLUTION REMAIN COMPLEX AND UNCERTAIN. LATEST 18Z NAM-WRF SHOWS LIMITED QPF SIGNAL ON THE MISSOURI RIVER WITH MORE ROBUST POTENTIAL EAST ALONG THE WARM FRONT INTO MN/WI THIS EVENING. MOST LIKELY REASON FOR THESE VARIOUS SCENARIOS IS THE LACK OF MORE PRONOUNCED LARGE SCALE FORCING FOR ASCENT ACROSS THE AREA UNTIL LATER THIS EVENING WHEN A SHORT WAVE TROUGH NOW ACROSS MT BEGINS TO INFLUENCE THE REGION. IF PERSISTENT MESOSCALE FORCING IN THE ABSENCE OF STRONGER FORCING ALONG THE BOUNDARIES CAN PROMOTE STORM DEVELOPMENT IN THE NEXT COUPLE OF HOURS...MAGNITUDE OF CAPE AND SHEAR IN PLACE WOULD CONTRIBUTE TO POSSIBLE SUPERCELLS WITH THE THREAT OF VERY LARGE HAIL AND LOCALLY DAMAGING WINDS. WHILE WEAK LOW LEVEL WINDS OVER MOST OF THE AREA SHOULD NEGATE GREATER TORNADO THREAT...ENHANCED SHEAR NEAR BOUNDARY/FRONT/TROUGH INTERSECTIONS...COINCIDENT WITH STORM DEVELOPMENT IN SUCH AN UNSTABLE REGIME...MIGHT RESULT IN A HIGHER CHANCE FOR A TORNADO OR TWO. THE REGION WILL CONTINUE TO BE MONITORED AND A WATCH IS POSSIBLE IF THIS DEVELOPMENT BEGINS TO OCCUR. ..CARBIN.. 05/02/2012 ATTN...WFO...ARX...MPX...DMX...FSD...OAX...GID...LBF... LAT...LON 42349639 40879786 40729851 41079867 42649801 43519752 43969702 44309643 44609527 44749466 44759388 44629319 44529301 44119245 43749272 43339395 42789580 42349639



MD0667


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MD0667 Text


MESOSCALE DISCUSSION 0667 NWS STORM PREDICTION CENTER NORMAN OK 0738 PM CDT WED MAY 02 2012 AREAS AFFECTED...SRN MN INTO WRN/CENTRAL WI CONCERNING...SEVERE THUNDERSTORM WATCH 225... VALID 030038Z - 030115Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 225 CONTINUES. SUMMARY...A NEW WW WILL BE COORDINATED SOON FOR WRN WI. SVR WEATHER THREAT CONTINUES ACROSS SRN/SRN MN WITH ACTIVITY EXPECTED TO PERSIST AND MOVE INTO WRN WI. HAIL AND STRONG WIND GUSTS WILL REMAIN THE PRIMARY THREATS. DISCUSSION...REGIONAL RADAR IMAGERY SHOWED SEVERAL STRONG TO SEVERE STORMS EXTENDING FROM SOUTH CENTRAL INTO SRN MN...WITH ACTIVITY EXPECTED TO MOVE INTO WRN WI SOON. THE AIR MASS DOWNSTREAM OVER WRN WI IS GRADUALLY DESTABILIZING WITH SIMILAR BULK SHEAR TO OVER SRN MN /UP TO 50 KT/ FAVORING ORGANIZED STORMS. STEEP LAPSE RATES FAVOR A THREAT FOR HAIL AND DAMAGING WINDS. ..PETERS.. 05/03/2012 ATTN...WFO...GRB...MKX...ARX...MPX...DMX...FSD... LAT...LON 44129569 44479458 44679231 44689034 44288958 43608959 43469144 43509338 43549516 43589592 44129569