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May 5, 2012 - 1st Nebraska Chase

Location:

Northeast Nebraska

Target:

Yankton, SD

Tornadoes:

0

Miles:

760


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Chased with Jacob today. A very vigorous warm front was progged to setup over southeast South Dakota. Ridiculously high cape values (4000+) combined with a ton of wind shear on the warm front lead to the SPC putting out a hatched 10% risk over southeast South Dakota/northeast Nebraska.

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We targeted Yankton as we figured we could decide from there whether or not we needed to cross the river and go into Nebraska. The hope was that we could stay in South Dakota to avoid any issues with chaser convergence in getting back across the river when storms crossed the river. Mother nature took care of that for us though as the early morning convection prevented the warm front from lifting as far north as was initially thought and thus we had to go south into Nebraska. We first sat near the town of Magnet around 3pm and watched for awhile. There was some cumulus in the area so it actually looked like things might go up soon. Eventually the cumulus went away though so we decided to head west near Creighton where there was still some cumulus. We sat in front of a field and watched numerous towers try to go up.

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We must have seen 10-15 individual towers try to go up, each one getting a little higher but then toppling over and then all of the sudden a really nice tower started going up. We thought for sure this one was going to do it and even the SPC pulled the trigger on issuing a tornado watch but eventually this one also toppled over.

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After that tower failed, nothing really tried again to go up. It was so hot that we used the tail gate of Jacobís car as shade and a view finder.

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We gave it probably another hour but it became obvious that the cap wasnít going to break so we headed north towards an elevated supercell in South Dakota. Along the way we drove through some beautiful terrain with rolling hills and then stopped for some photos at the Missouri river crossing.

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Eventually we caught up to the supercell near Mitchell, SD but it didnít look too impressive. As we drove east along side this thing, we encountered some insane inflow winds so we decided to pull over and get some video. We estimated that the winds were close to 50mph. There was debris blowing everywhere and the car was shaking like crazy. The best part was that when we started heading east again, there was a cow on the side of the road peeing and you could see the piss blowing everywhere with the wind! It was even blowing all over another cow standing right next to him. It was absolutely hilarious. Definitely put a nice mark on an unfortunate day. So, my first chase in Nebraska was a bust but we still got to see storms, we got to see some beautiful terrain and the cow pissing in 50mph wind was icing on the cake.
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SPC Text


SPC AC 050600 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT SAT MAY 05 2012 VALID 051200Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF THE N-CNTRL CONUS TODAY THROUGH TONIGHT... ...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF N/W-CNTRL TX THIS AFTERNOON... ...SYNOPSIS... PRIMARY SHORT WAVE IMPULSE EMBEDDED WITHIN THE AMPLIFIED UPPER-LEVEL TROUGH OVER THE WRN CONUS WILL SHIFT E/NEWD ACROSS THE NRN ROCKIES TOWARDS THE CANADIAN BORDER IN THE NRN HIGH PLAINS...AS IT IMPINGES ACROSS THE CNTRL CONUS RIDGE. BELT OF STRONG MID-LEVEL W/SWLYS WILL BECOME CENTERED FROM THE CNTRL ROCKIES TO THE UPPER MS VALLEY THIS AFTERNOON. AT THE SURFACE...DIFFUSE QUASI-STATIONARY FRONT ACROSS IA/NEB SHOULD ADVANCE N/NWWD INTO PARTS OF SD AND FAR SRN MN...WITH A WEAK TRIPLE POINT CYCLONE INVOF N-CNTRL NEB. DURING THE LATTER HALF OF THE PERIOD...A COLD FRONT WILL SWEEP E/SWD ACROSS THE NRN/CNTRL PLAINS...WITH A WEAK SURFACE CYCLONE CONTINUING EWD ACROSS THE MID-MO VALLEY/UPPER MIDWEST. ELSEWHERE...A WEAK UPPER-LEVEL IMPULSE CENTERED OVER BAJA CA SUR SHOULD PROGRESS TOWARDS THE BIG BEND OF WRN TX BY LATE AFTERNOON...WITH THE DRYLINE EXTENDING FROM WRN OK TO THE EDWARDS PLATEAU OF TX. WEAK MID-LEVEL IMPULSE OVER THE OZARK PLATEAU SHOULD DRIFT SEWD INTO THE LOWER MS VALLEY. ...N-CNTRL CONUS... SUBTLE DIFFERENCES EXIST AMONG MODEL GUIDANCE WITH THE PLACEMENT OF THE AFOREMENTIONED SURFACE FEATURES...WHICH WILL LIKELY BE MODULATED BY POTENTIAL CONVECTION DEVELOPING THIS MORNING N OF THE FRONT WITHIN A LOW-LEVEL UPSLOPE/WAA REGIME. ENVIRONMENT INVOF THE FRONT/RESIDUAL CONVECTIVE OUTFLOWS WILL BE BECOME INCREASINGLY UNSTABLE AS 60S SURFACE DEW POINTS OVERSPREAD S-CNTRL/SERN SD AND FAR SRN MN BENEATH STEEP MID-LEVEL LAPSE RATES. WARM SECTOR ACROSS THE MID-MO VALLEY WILL LIKELY BECOME STRONGLY BUOYANT BY LATE AFTERNOON WITH MLCAPE OF 3500-4500 J/KG. ON THE FRINGE OF THE STRONGER MID-LEVEL SWLYS...SUBSTANTIAL VEERING OF THE WIND PROFILE WITH HEIGHT WILL RESULT IN HODOGRAPHS HIGHLY FAVORABLE FOR ROTATING STORMS...ESPECIALLY JUST E OF THE TRIPLE POINT LOW ALONG THE QUASI-STATIONARY/WARM FRONT. AT LEAST ISOLATED TSTM DEVELOPMENT APPEARS PROBABLE HERE AND ALSO FARTHER WEST TO THE BLACK HILLS DURING MID-LATE AFTERNOON. RAPID GROWTH INTO SUPERCELLS CAPABLE OF VERY LARGE HAIL AND TORNADOES SHOULD OCCUR OVER NERN NEB/SERN SD INTO PARTS OF NWRN IA/FAR SWRN MN. AS THE COLD FRONT ACCELERATES ACROSS THE NRN/CNTRL PLAINS DURING THE EVENING/OVERNIGHT...UPSCALE GROWTH INTO ONE OR MORE MCS/S APPEARS LIKELY...DEVELOPING EWD IN THE UPPER MIDWEST AND EVENTUALLY SWWD ACROSS THE MID-MO VAL ...PARTS OF N-CNTRL TX TO THE EDWARDS PLATEAU... STRONG TO EXTREME INSTABILITY WILL BE PREVALENT AGAIN E OF A WELL-DEFINED DRYLINE WITH 700-500 MB LAPSE RATES NEAR 9 C/KM. WITH APPROACH OF A WEAK UPPER-LEVEL IMPULSE...ASCENT SHOULD BE SUFFICIENT FOR ISOLATED TSTMS TO FORM ALONG THE DRYLINE IN THE LATE AFTERNOON. INTENSITY/COVERAGE SHOULD BE SOMEWHAT LESS RELATIVE TO FRI OWING TO MORE MODEST MID-LEVEL WLYS. STILL EFFECTIVE SHEAR AROUND 25-30 KT WOULD SUPPORT MARGINAL SUPERCELL STRUCTURES GIVEN THE DEGREE OF BUOYANCY FAVORABLE FOR ISOLATED LARGE HAIL. ...SRN APPALACHIANS/CAROLINAS... AHEAD OF ONGOING CONVECTION THIS MORNING OVER THE OH VALLEY...A BROAD WARM SECTOR WILL REMAIN PREVALENT. DIURNAL HEATING SHOULD SUPPORT SCATTERED CLUSTERS OF TSTMS REDEVELOPING DURING THE AFTERNOON TOWARDS THE CAROLINA COAST. ALTHOUGH LOW-LEVEL FLOW SHOULD REMAIN WEAK...AREAS OF ENHANCED MID-LEVEL NWLYS /TIED TO PERHAPS REMNANT MCV/S FROM THE MORNING CONVECTION/ COULD SUPPORT AN ORGANIZED CLUSTER OR TWO CAPABLE OF ISOLATED DAMAGING WINDS. WILL DEFER TO LATER OUTLOOKS FOR A POSSIBLE UPGRADE TO SLIGHT RISK. ..GRAMS/HURLBUT.. 05/05/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z

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SPC AC 051257 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0757 AM CDT SAT MAY 05 2012 VALID 051300Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVR PARTS OF THE NRN PLNS AND UPR MS VLY... ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SERN STATES... ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF TX... ...SYNOPSIS... CLOSED LOW NOW OVER NW MT WILL PROGRESS E TO SRN SK THIS PERIOD AS ATTENDANT TROUGH REACHES THE NRN HI PLNS/ERN GRT BASIN. AHEAD OF THE MAIN TROUGH...SATELLITE AND UPR AIR ANALYSES SHOW A STREAM OF ENHANCED SWLY FLOW WITH EMBEDDED SMALL-SCALE DISTURBANCES ATTM EXTENDING FROM ERN UT AND WY INTO THE WRN DAKOTAS. THIS BELT OF ENHANCED FLOW SHOULD SHIFT EWD ACROSS THE NRN PLNS TODAY...AHEAD OF THE MAIN TROUGH...AS BROAD RIDGE CONTINUES OVER THE MID MS AND OH VLYS. AT THE SFC...WRN PART OF DIFFUSE FRONT ATTM EXTENDING FROM THE NEB/SD BORDER AREA ESE INTO THE LWR OH VLY EXPECTED TO EDGE NWD INTO SRN/ERN SD AND FAR SRN MN TODAY...WITH A WEAK TRIPLE POINT LOW FORMING OVER N CNTRL NEB. LATER TODAY AND TNGT...A COLD FRONT SHOULD BECOME BETTER DEFINED OVER THE NRN HI PLNS. THIS FEATURE WILL THEN SWEEP E/SE ACROSS THE NRN/CNTRL PLNS...WITH A WEAK SFC LOW CONTINUING E ACROSS THE MID MO VLY/UPR MIDWEST. ELSEWHERE...AN UPR LVL IMPULSE NOW OVER BAJA CA SHOULD PROGRESS NE TOWARD THE TX BIG BEND BY LATE AFTN...WITH THE SFC DRYLINE EXTENDING FROM WRN OK TO THE EDWARDS PLATEAU. FARTHER E...WEAK UPR DISTURBANCE NOW OVER E TX SHOULD TRACK ESE ACROSS THE LWR MS VLY. ...N CNTRL STATES TODAY/TNGT... REGION INVOF AFOREMENTIONED FRONT AND OUTFLOW BOUNDARIES OVER SRN SD....NRN/ERN NEB...NW IA...AND SW MN WILL BE BECOME VERY UNSTABLE AS 60S SFC DEW POINTS OVERSPREAD REGION BENEATH STEEP MID LVL LAPSE RATES...WITH LATE AFTN SBCAPE EXPECTED TO RANGE FROM 2000 TO 4000 J/KG. CONTINUED EWD ADVANCE OF LEAD UPR LVL DISTURBANCES AHEAD OF MAIN WRN STATES TROUGH...AND SUBSTANTIAL DEGREE OF VERTICAL VEERING IN THE WIND PROFILES...WILL RESULT IN HODOGRAPHS VERY FAVORABLE FOR ROTATING STORMS...ESPECIALLY E OF THE TRIPLE POINT LOW ALONG THE QSTNRY/WARM FRONT. AT LEAST ISOLD TSTM DEVELOPMENT APPEARS LIKELY THERE...AND ALSO FARTHER W INTO THE BLACK HILLS DURING MID-LATE AFTN. RAPID GROWTH INTO SUPERCELLS CAPABLE OF VERY LARGE HAIL AND TORNADOES MAY OCCUR...ESPECIALLY OVER NERN NEB/SE SD INTO PARTS OF NW IA AND FAR SW MN. AS THE COLD FRONT ACCELERATES E/SE ACROSS THE NRN/CNTRL PLNS TNGT...UPSCALE DEVELOPMENT INTO ONE OR MORE MCSS APPEARS LIKELY. THESE MAY POSE A GRADUALLY DIMINISHING SVR THREAT EWD IN THE UPR MS VLY AND SWD INTO THE MID MO VLY EARLY SUN. ...PARTS OF CNTRL AND SRN TX THIS AFTN/EVE... STRONG TO EXTREME INSTABILITY WILL ONCE AGAIN DEVELOP WITH AFTN HEATING E OF DRYLINE IN CNTRL AND SRN TX...WITH 700-500 MB LAPSE RATES NEAR 9 C/KM. COUPLED WITH APPROACH OF UPR LVL IMPULSE...SETUP MAY YIELD ISOLD LATE DAY TSTMS ALONG AND POSSIBLY AHEAD OF DRYLINE. INTENSITY/COVERAGE SHOULD BE SOMEWHAT LESS THAN YESTERDAY OWING TO WEAKER MID LVL WLYS. BUT 25-30 KT WNWLY DEEP SHEAR COULD FOSTER A FEW SUPERCELLS/SUSTAINED STORMS WITH LARGE HAIL/LOCALLY DMGG WIND GIVEN STRONG BUOYANCY. ...GA/SC/SRN NC THIS AFTN... FAIRLY STRONG DIURNAL DESTABILIZATION /WITH INCREASING TO SBCAPE TO 2000 J PER KG/ SHOULD OCCUR OVER PARTS OF GA...SC...AND NC TODAY AHEAD OF OVERNIGHT CONVECTIVE SYSTEMS IN THE OH/TN VLYS. COUPLED WITH PRESENCE OF MODERATE WNWLY MID LVL FLOW AND ERN EXTENSION OF EML PLUME...ENVIRONMENT COULD SUPPORT REDEVELOPMENT OF STRONG TO POSSIBLY SVR PULSE STORMS THIS AFTN OVER PIEDMONT PORTIONS OF GA/SC AND NC. FCST WIND PROFILES AND THE PRESENCE OF EXITING OUTFLOW BOUNDARIES TO FOCUS LOW LVL UPLIFT SUGGEST THE POSSIBILITY FOR DEVELOPMENT OF FORWARD-PROPAGATING/SE-MOVING BANDS OF STORMS THAT COULD YIELD DMGG WIND/SVR HAIL THROUGH EARLY EVE. ..CORFIDI/GARNER.. 05/05/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z

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SPC AC 051620 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1120 AM CDT SAT MAY 05 2012 VALID 051630Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE NRN PLAINS AND UPPER MS VALLEY INTO MID AND LOWER MO VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE CAROLINAS INTO THE LOWER MS VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE SRN PLAINS... ...SYNOPSIS... UPPER LOW OVER THE NRN ROCKIES WILL PROGRESS NEWD INTO SRN SASKATCHEWAN THIS PERIOD IN TANDEM WITH A 50-60 KT MIDLEVEL JET STREAK DEVELOPING FROM THE ERN GREAT BASIN AND CNTRL ROCKIES INTO NRN PLAINS. ELSEWHERE...A MIDLEVEL IMPULSE --OF CONVECTIVE ORIGIN-- OVER THE CNTRL APPALACHIANS WILL PROGRESS SEWD ACROSS VA/NC/SC...TO THE E OF A SHORTWAVE TROUGH ADVANCING INTO THE LOWER MS VALLEY. AT THE SURFACE...CURRENT ANALYSIS SHOWS AN AREA OF LOW PRESSURE OVER WRN KS WITH AN ASSOCIATED WARM/STATIONARY FRONT EXTENDING NNEWD INTO N-CNTRL/NERN NEB BEFORE CURVING SEWD THROUGH CNTRL IA INTO CNTRL IL/SRN IND. AIDED BY CONVECTIVE OUTFLOW AND THE DEVELOPMENT OF A FRONTAL WAVE...THIS BOUNDARY IS EXPECTED TO INTENSIFY TODAY ACROSS THE MID-MO VALLEY...TO THE W OF A WEAK COLD FRONT WHICH WILL BE REINFORCED TONIGHT BY A PACIFIC FRONT MOVING OUT OF THE ROCKIES. ...NRN PLAINS/UPPER MS VALLEY INTO MID AND LOWER MO VALLEY... ELEVATED SUPERCELLS ARE ONGOING THIS MORNING OVER SERN SD/SWRN MN WITHIN THE EXIT REGION OF 20-30 KT LLJ WHERE WAA AND ISENTROPIC ASCENT ARE BEING ENHANCED. 12Z OAX SOUNDING IS LIKELY A PROXY FOR THE INFLOW AIR MASS THAT IS BEING LIFTED ABOVE COMPOSITE BOUNDARY...FEATURING A MOIST BOUNDARY LAYER AND STEEP MIDLEVEL LAPSE RATES WITH MUCAPE OF 2000-3000 J/KG. GIVEN THE GRADUAL INTENSIFICATION AND BROADENING OF THE LLJ TODAY...EXPECT ONGOING ELEVATED STORMS TO PERSIST ACROSS PORTIONS OF SRN MN WITH A CONTINUED RISK FOR LARGE HAIL. BASED ON LATEST SURFACE OBSERVATIONS...IT APPEARS ACTIVE COLD POOL ASSOCIATED WITH SD STORMS MAY DISPLACE EFFECTIVE SURFACE BOUNDARY A BIT FARTHER TO THE S INTO NRN NEB THAN MODEL GUIDANCE SUGGESTS. TO THE S OF THIS BOUNDARY...THE EROSION OF LOW CLOUDS WILL ALLOW FOR STRONG DIABATIC HEATING TO OCCUR. WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE MID 60S-LOWER 70S AND THE STEEP MIDLEVEL LAPSE RATES...EXPECT AFTERNOON MLCAPE VALUES TO APPROACH 2500-3500 J/KG. PERSISTENT LOW-LEVEL WAA...CONVERGENCE ALONG THE FRONT AND WEAK MIDLEVEL HEIGHT FALLS ARE EXPECTED TO CONTRIBUTE TO SURFACE-BASED TSTM DEVELOPMENT THIS AFTERNOON OVER THE MID-MO VALLEY WITHIN A KINEMATIC ENVIRONMENT CHARACTERIZED BY A VERTICALLY VEERING WIND PROFILE AND STEADILY STRENGTHENING LOW AND DEEP-LAYER SHEAR. AS SUCH...SETUP WILL BE QUITE CONDUCIVE TO SUPERCELL EVOLUTION WITH AN ATTENDANT RISK FOR TORNADOES...VERY LARGE HAIL AND DAMAGING WINDS. UPSCALE GROWTH OF STORMS INTO AN MCS OR TWO APPEARS LIKELY TONIGHT WITH A CONTINUED THREAT FOR DAMAGING WINDS AND HAIL. ...CAROLINAS THIS AFTERNOON/EVENING... SEWD PROGRESSION OF MIDLEVEL IMPULSE MENTIONED IN SYNOPSIS WILL COMBINE WITH LOW-LEVEL UPLIFT ALONG LEE TROUGH AND DEVELOPING SEA BREEZE BOUNDARIES TO GIVE RISE TO SCATTERED TSTMS THIS AFTERNOON. MODIFICATION OF 12Z CHS/MHX SOUNDINGS FOR SURFACE TEMPERATURES IN THE MID-UPPER 80S YIELDS SBCAPE VALUES OF 2000-2500 J/KG WITH LITTLE OR NO INHIBITION. WHEN COUPLED WITH 30-35 KT OF DEEP NWLY SHEAR...SETUP WILL SUPPORT MULTICELLS AND LINE SEGMENTS CAPABLE OF DAMAGING WINDS AND HAIL INTO THIS EVENING. ...LOWER MS VALLEY INTO GA THIS AFTERNOON/EVENING... VISIBLE SATELLITE AND SURFACE OBSERVATIONS SHOW A WELL-DEFINED OUTFLOW BOUNDARY ADVANCING SWD/SWWD THROUGH WRN TN AND NRN PARTS OF AL/GA. THIS FEATURE AND SLOW EWD MOVEMENT OF SHORTWAVE TROUGH INTO THE LOWER MS VALLEY SHOULD SUPPORT WIDELY SCATTERED TSTM DEVELOPMENT LATER TODAY. 12Z REGIONAL SOUNDINGS SHOW THE PRESENCE OF MIDLEVEL LAPSE RATES OF 7.5-8.5 C/KM ATOP A MOIST BOUNDARY LAYER WHICH WILL CONTRIBUTE TO MODERATE-STRONG AFTERNOON INSTABILITY. THOUGH VERTICAL SHEAR WILL REMAIN WEAK...THE THERMODYNAMIC ENVIRONMENT WILL PROMOTE VIGOROUS UP/DOWNDRAFTS CAPABLE OF SEVERE HAIL AND DAMAGING WINDS. ...SRN PLAINS THIS AFTERNOON/EVENING... IN THE ABSENCE OF APPRECIABLE LARGE-SCALE FORCING FOR ASCENT...STRONG DAYTIME HEATING AND A DEEPENING DRYLINE CIRCULATION MAY FOSTER ISOLATED-WIDELY SCATTERED TSTM DEVELOPMENT AGAIN THIS AFTERNOON. HERE...THE COMBINATION OF VERY STEEP LAPSE RATES...MLCAPE OF 2000-3000+ J/KG AND AROUND 30 KT OF DEEP NWLY SHEAR WILL SUPPORT SUPERCELL STORM MODES WITH A RISK FOR LARGE HAIL AND DAMAGING WIND GUSTS. ..MEAD/LEITMAN.. 05/05/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z

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SPC Text


SPC AC 051959 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0259 PM CDT SAT MAY 05 2012 VALID 052000Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL PLAINS...NRN PLAINS...UPPER MIDWEST AND MID-MO VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GULF COAST STATES AND CAROLINAS... THE ONLY CHANGE TO THE OUTLOOK IS TO EXTEND THE SLIGHT RISK AREA FURTHER TO THE EAST ACROSS SW WI AND INTO NWRN IL WHERE A LINEAR MCS IS EXPECTED TO TRACK. FURTHER TO THE WEST...THUNDERSTORMS ARE EXPECTED TO INITIATE LATE THIS AFTERNOON IN SERN SD AND NERN NEB WHERE THE ENVIRONMENT IS CONDUCIVE FOR SUPERCELLS AND TORNADOES. THE MODELS APPEAR TO BE DEVELOPING STORMS TOO FAR TO THE NORTHWEST IN ECNTRL SD WHERE THE AIRMASS IS COOLER AND LESS UNSTABLE. FOR THIS REASON...WILL LEAVE THE HATCHED AREAS WITH THE 10 PERCENT TORNADO AND 30 PERCENT HAIL PROBABILITIES AS IS FURTHER TO THE SOUTHEAST. ELSEWHERE ACROSS THE CONUS...THE SLIGHT RISK AREAS IN THE GULF COAST STATES AND IN THE SRN PLAINS ARE ALIGNED ALONG THE AXIS OF STRONGEST INSTABILITY SUGGESTING NO CHANGES ARE NEEDED THERE. ..BROYLES.. 05/05/2012 .PREV DISCUSSION... /ISSUED 1120 AM CDT SAT MAY 05 2012/ ...SYNOPSIS... UPPER LOW OVER THE NRN ROCKIES WILL PROGRESS NEWD INTO SRN SASKATCHEWAN THIS PERIOD IN TANDEM WITH A 50-60 KT MIDLEVEL JET STREAK DEVELOPING FROM THE ERN GREAT BASIN AND CNTRL ROCKIES INTO NRN PLAINS. ELSEWHERE...A MIDLEVEL IMPULSE --OF CONVECTIVE ORIGIN-- OVER THE CNTRL APPALACHIANS WILL PROGRESS SEWD ACROSS VA/NC/SC...TO THE E OF A SHORTWAVE TROUGH ADVANCING INTO THE LOWER MS VALLEY. AT THE SURFACE...CURRENT ANALYSIS SHOWS AN AREA OF LOW PRESSURE OVER WRN KS WITH AN ASSOCIATED WARM/STATIONARY FRONT EXTENDING NNEWD INTO N-CNTRL/NERN NEB BEFORE CURVING SEWD THROUGH CNTRL IA INTO CNTRL IL/SRN IND. AIDED BY CONVECTIVE OUTFLOW AND THE DEVELOPMENT OF A FRONTAL WAVE...THIS BOUNDARY IS EXPECTED TO INTENSIFY TODAY ACROSS THE MID-MO VALLEY...TO THE W OF A WEAK COLD FRONT WHICH WILL BE REINFORCED TONIGHT BY A PACIFIC FRONT MOVING OUT OF THE ROCKIES. ...NRN PLAINS/UPPER MS VALLEY INTO MID AND LOWER MO VALLEY... ELEVATED SUPERCELLS ARE ONGOING THIS MORNING OVER SERN SD/SWRN MN WITHIN THE EXIT REGION OF 20-30 KT LLJ WHERE WAA AND ISENTROPIC ASCENT ARE BEING ENHANCED. 12Z OAX SOUNDING IS LIKELY A PROXY FOR THE INFLOW AIR MASS THAT IS BEING LIFTED ABOVE COMPOSITE BOUNDARY...FEATURING A MOIST BOUNDARY LAYER AND STEEP MIDLEVEL LAPSE RATES WITH MUCAPE OF 2000-3000 J/KG. GIVEN THE GRADUAL INTENSIFICATION AND BROADENING OF THE LLJ TODAY...EXPECT ONGOING ELEVATED STORMS TO PERSIST ACROSS PORTIONS OF SRN MN WITH A CONTINUED RISK FOR LARGE HAIL. BASED ON LATEST SURFACE OBSERVATIONS...IT APPEARS ACTIVE COLD POOL ASSOCIATED WITH SD STORMS MAY DISPLACE EFFECTIVE SURFACE BOUNDARY A BIT FARTHER TO THE S INTO NRN NEB THAN MODEL GUIDANCE SUGGESTS. TO THE S OF THIS BOUNDARY...THE EROSION OF LOW CLOUDS WILL ALLOW FOR STRONG DIABATIC HEATING TO OCCUR. WHEN COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE MID 60S-LOWER 70S AND THE STEEP MIDLEVEL LAPSE RATES...EXPECT AFTERNOON MLCAPE VALUES TO APPROACH 2500-3500 J/KG. PERSISTENT LOW-LEVEL WAA...CONVERGENCE ALONG THE FRONT AND WEAK MIDLEVEL HEIGHT FALLS ARE EXPECTED TO CONTRIBUTE TO SURFACE-BASED TSTM DEVELOPMENT THIS AFTERNOON OVER THE MID-MO VALLEY WITHIN A KINEMATIC ENVIRONMENT CHARACTERIZED BY A VERTICALLY VEERING WIND PROFILE AND STEADILY STRENGTHENING LOW AND DEEP-LAYER SHEAR. AS SUCH...SETUP WILL BE QUITE CONDUCIVE TO SUPERCELL EVOLUTION WITH AN ATTENDANT RISK FOR TORNADOES...VERY LARGE HAIL AND DAMAGING WINDS. UPSCALE GROWTH OF STORMS INTO AN MCS OR TWO APPEARS LIKELY TONIGHT WITH A CONTINUED THREAT FOR DAMAGING WINDS AND HAIL. ...CAROLINAS THIS AFTERNOON/EVENING... SEWD PROGRESSION OF MIDLEVEL IMPULSE MENTIONED IN SYNOPSIS WILL COMBINE WITH LOW-LEVEL UPLIFT ALONG LEE TROUGH AND DEVELOPING SEA BREEZE BOUNDARIES TO GIVE RISE TO SCATTERED TSTMS THIS AFTERNOON. MODIFICATION OF 12Z CHS/MHX SOUNDINGS FOR SURFACE TEMPERATURES IN THE MID-UPPER 80S YIELDS SBCAPE VALUES OF 2000-2500 J/KG WITH LITTLE OR NO INHIBITION. WHEN COUPLED WITH 30-35 KT OF DEEP NWLY SHEAR...SETUP WILL SUPPORT MULTICELLS AND LINE SEGMENTS CAPABLE OF DAMAGING WINDS AND HAIL INTO THIS EVENING. ...LOWER MS VALLEY INTO GA THIS AFTERNOON/EVENING... VISIBLE SATELLITE AND SURFACE OBSERVATIONS SHOW A WELL-DEFINED OUTFLOW BOUNDARY ADVANCING SWD/SWWD THROUGH WRN TN AND NRN PARTS OF AL/GA. THIS FEATURE AND SLOW EWD MOVEMENT OF SHORTWAVE TROUGH INTO THE LOWER MS VALLEY SHOULD SUPPORT WIDELY SCATTERED TSTM DEVELOPMENT LATER TODAY. 12Z REGIONAL SOUNDINGS SHOW THE PRESENCE OF MIDLEVEL LAPSE RATES OF 7.5-8.5 C/KM ATOP A MOIST BOUNDARY LAYER WHICH WILL CONTRIBUTE TO MODERATE-STRONG AFTERNOON INSTABILITY. THOUGH VERTICAL SHEAR WILL REMAIN WEAK...THE THERMODYNAMIC ENVIRONMENT WILL PROMOTE VIGOROUS UP/DOWNDRAFTS CAPABLE OF SEVERE HAIL AND DAMAGING WINDS. ...SRN PLAINS THIS AFTERNOON/EVENING... IN THE ABSENCE OF APPRECIABLE LARGE-SCALE FORCING FOR ASCENT...STRONG DAYTIME HEATING AND A DEEPENING DRYLINE CIRCULATION MAY FOSTER ISOLATED-WIDELY SCATTERED TSTM DEVELOPMENT AGAIN THIS AFTERNOON. HERE...THE COMBINATION OF VERY STEEP LAPSE RATES...MLCAPE OF 2000-3000+ J/KG AND AROUND 30 KT OF DEEP NWLY SHEAR WILL SUPPORT SUPERCELL STORM MODES WITH A RISK FOR LARGE HAIL AND DAMAGING WIND GUSTS. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z

MD0712


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MESOSCALE DISCUSSION 0712 NWS STORM PREDICTION CENTER NORMAN OK 0950 AM CDT SAT MAY 05 2012 AREAS AFFECTED...CNTRL/SERN SD...SWRN MN...NWRN IA CONCERNING...SEVERE THUNDERSTORM WATCH 247... VALID 051450Z - 051545Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 247 CONTINUES. SUMMARY...HAIL REMAINS LIKELY WITH MCS ACTIVITY AS IT SPREADS ACROSS CNTRL/SERN SD INTO THE UPPER MS VALLEY. NEW SEVERE THUNDERSTORM WATCH WILL LIKELY BE REQUIRED INTO PORTIONS OF SRN MN IN THE NEXT HOUR. DISCUSSION...TWO MCS CLUSTERS HAVE EVOLVED ACROSS SD THIS MORNING. THE LEAD MCS IS SPREADING EWD ACROSS CNTRL PORTIONS OF WW247 AND EXHIBITS SEVERAL STOUT UPDRAFTS THAT ARE LIKELY PRODUCING VERY LARGE HAIL OVER MCCOOK AND DAVISON COUNTIES. THE SECOND MCS WILL SOON SPREAD INTO THE WRN PARTS OF THE WATCH. THIS ACTIVITY HAS EVOLVED WITHIN A ZONE OF FAVORABLE LOW LEVEL WARM ADVECTION AND THE LIKELIHOOD OF MCS MAINTENANCE IS HIGH GIVEN THAT THE LLJ SHOULD STRENGTHEN ACROSS SERN SD INTO THE EARLY AFTERNOON HOURS. WITH TIME SEVERE ELEVATED STORMS SHOULD PROGRESS INTO SWRN MN...PERHAPS DEVELOPING INTO THE EXTREME NWRN PARTS OF IA. ..DARROW.. 05/05/2012 ATTN...WFO...MPX...DMX...FSD...ABR...UNR... LAT...LON 44709978 44739402 43499427 43329971 44709978



MD0714


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MD0714 Text


MESOSCALE DISCUSSION 0714 NWS STORM PREDICTION CENTER NORMAN OK 0209 PM CDT SAT MAY 05 2012 AREAS AFFECTED...CNTRL/NERN NEB...SERN SD...NWRN IA CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 051909Z - 052045Z PROBABILITY OF WATCH ISSUANCE...95 PERCENT SUMMARY...TORNADO WATCH WILL BE NEEDED TO ADDRESS THE DEVELOPING SEVERE THREAT FROM CNTRL/NERN NEB...NEWD INTO NWRN IA. THIS WATCH WILL LIKELY BE ISSUED BY 21Z. DISCUSSION...EARLY MORNING MCS ACTIVITY THAT SPREAD ACROSS SD INTO MN HAS REINFORCED A BOUNDARY THAT CURRENTLY EXTENDS FROM CNTRL NEB INTO THE NWRN CORNER OF IA. WHILE THIS BOUNDARY MAY CONTINUE TO SAG SWD ACROSS PARTS OF NRN IA...STRONG HEATING OVER NEB WILL LIKELY PREVENT ANY FURTHER SWD PUSH ACROSS THE CNTRL PLAINS. WARM SECTOR CU FIELD APPEARS TO BE EXPANDING AND CHANGING CHARACTER ACROSS NERN NEB INTO NWRN IA PER DEEPENING BOUNDARY LAYER. IN ALL LIKELIHOOD THUNDERSTORMS WILL EVOLVE ALONG THE WIND SHIFT INITIALLY ACROSS NEB AS LOW LEVEL LAPSE RATES ARE SOMEWHAT STEEPER ACROSS THIS REGION. NEEDLESS TO SAY EXTREME INSTABILITY...SBCAPE IN EXCESS OF 4000 J/KG...AND DEEP LAYER SHEAR MORE THAN ADEQUATE TO SUPPORT ROTATING UPDRAFTS...WILL PROVE CONDUCIVE FOR SUPERCELLS...POTENTIALLY TORNADIC. VERY LARGE HAIL IS ALSO POSSIBLE WITH THIS ACTIVITY AND A WATCH WILL BE ISSUED BY 21Z. ..DARROW.. 05/05/2012 ATTN...WFO...DMX...FSD...OAX...GID...LBF... LAT...LON 41259972 42769775 43189498 42339381 41469641 40599852 41259972



MD0716


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MD0716 Text


MESOSCALE DISCUSSION 0716 NWS STORM PREDICTION CENTER NORMAN OK 0352 PM CDT SAT MAY 05 2012 AREAS AFFECTED...CNTRL-NERN NEB / SERN SD / NWRN IA CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY VALID 052052Z - 052215Z PROBABILITY OF WATCH ISSUANCE...95 PERCENT SUMMARY...SUPERCELLS CAPABLE OF TORNADOES...VERY LARGE HAIL...AND DAMAGING WIND GUSTS ARE EXPECTED TO DEVELOP PRIOR TO 00Z...REQUIRING A TORNADO WATCH. DISCUSSION...20Z SURFACE ANALYSIS SHOWED A SURFACE LOW W OF MCK WITH AN ASSOCIATED STATIONARY BOUNDARY EXTENDING NEWD TO N OF OFK AND SUX BEFORE CURVING SEWD THROUGH CNTRL IA. AIR MASS ALONG AND S OF THIS BOUNDARY HAS WARMED INTO THE UPPER 80S-LOWER 90S AND WHEN COUPLED WITH DEWPOINTS IN THE MID-UPPER 60S...IS RESULTING IN MLCAPE VALUES OF 3000-4000 J/KG AND A WEAKENING CAP. THOUGH LOW-LEVEL WAA PERSISTS...MIDLEVEL HEIGHTS APPEAR TO BE STILL SLIGHTLY RISING AHEAD OF NRN ROCKIES UPPER TROUGH. AS SUCH...IT NOW APPEARS THAT STORM INITIATION MAY BE DELAYED TO CLOSER TO 00Z WHEN CONVERGENCE INCREASES IN THE EXIT REGION OF A STRENGTHENING LLJ. PRONOUNCED VEERING OF WINDS WITH HEIGHT AND STRENGTHENING LOW AND DEEP-LAYER SHEAR WILL SUPPORT THE RAPID EVOLUTION OF STORMS INTO SUPERCELLS WITH AN ASSOCIATED THREAT FOR TORNADOES...VERY LARGE HAIL AND DAMAGING WINDS. A TORNADO WATCH WILL BE REQUIRED PRIOR TO 00Z. ..MEAD.. 05/05/2012 ATTN...WFO...DMX...FSD...OAX...GID...LBF... LAT...LON 41249982 42219894 43039777 43359680 43329541 42789444 42339413 42039440 41989545 41919662 41379858 41069937 41099965 41249982



MD0721


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MD0721 Text


MESOSCALE DISCUSSION 0721 NWS STORM PREDICTION CENTER NORMAN OK 0621 PM CDT SAT MAY 05 2012 AREAS AFFECTED...PARTS OF N CNTRL NEB...SERN SD...SWRN MN...NWRN IA CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 052321Z - 060045Z PROBABILITY OF WATCH ISSUANCE...95 PERCENT SUMMARY...SEVERE STORMS ARE EXPECTED TO RAPIDLY INCREASE IN NUMBER AND INTENSITY EARLY THIS EVENING...WITH A RISK FOR LARGE HAIL THE PRIMARY INITIAL THREAT THROUGH 01-03Z. DISCUSSION...ISOLATED VIGOROUS CONVECTIVE DEVELOPMENT ALREADY APPEARS UNDERWAY ACROSS SOUTHEASTERN SOUTH DAKOTA...NORTH OF A FAIRLY SHARP SURFACE FRONTAL ZONE THAT HAS ADVANCED SOUTH OF BROKEN BOW AND NORTH PLATTE...WHILE REMAINING QUASI-STATIONARY NORTH OF NORFOLK THROUGH THE SIOUX CITY AREA...ON INTO CENTRAL IOWA. THIS IS BEING SUPPORTED BY LOW-LEVEL WARM ADVECTION...AND LIFT OF MOIST PARCELS TO LEVELS OF FREE CONVECTION...ABOVE THE FIRMLY ENTRENCHED COOL/STABLE NEAR SURFACE LAYER. EVEN TO THE NORTH OF THE FRONT...ACROSS MUCH SOUTHERN/EASTERN SOUTH DAKOTA...WARM ELEVATED MIXED LAYER AIR HAS BEEN TENDING TO INHIBIT CONVECTIVE DEVELOPMENT. HOWEVER...INHIBITION APPEARS LIKELY TO WEAKEN BY THE 01-03Z TIME FRAME...IF NOT BEFORE...AIDED BY INCREASING LARGE-SCALE MID-LEVEL FORCING DOWNSTREAM OF THE UPPER TROUGH LIFTING ACROSS THE NORTHERN ROCKIES...PERHAPS AIDED BY RADIATIVE PROCESSES. AS THIS OCCURS...A RAPID INCREASING IN STORM DEVELOPMENT APPEARS LIKELY IN THE PRESENCE OF STRONG CONVECTIVE LAYER SHEAR AND MOST UNSTABLE CAPE UP TO 2000-4000 J/KG. LARGE HAIL SHOULD BE THE PRIMARY THREAT INITIALLY...BEFORE ACTIVITY BEGINS TO CONSOLIDATE LATER THIS EVENING. ..KERR/THOMPSON.. 05/05/2012 ATTN...WFO...FSD...OAX...ABR...LBF...UNR... LAT...LON 43509963 44429835 44509750 44289650 43219635 42759849 42159953 41690083 43509963