Matt Molnar
2012-04-13, 09:08 PM
The National Weather Service is forecasting a significant tornado, hail and severe storm outbreak stretching from Oklahoma through Kansas, Nebraska and Iowa, more than 24 hours ahead of time. NWS has only issued such a dire prediction this far ahead of time once before, in April 2006. That time they were right: The next day, over 100 tornadoes killed a dozen people and damaged over 1,000 homes in the southeast.
The map below indicates the likelihood of severe weather impacting within 25 miles of any point within a shaded area.
http://www.spc.noaa.gov/products/outlook/day2probotlk_1730_any.gif
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT FRI APR 13 2012
VALID 141200Z - 151200Z
...THERE IS A HIGH RISK OF SVR TSTMS OVER ERN NEB AND FAR WRN IA...
...THERE IS A HIGH RISK OF SVR TSTMS FROM S CNTRL KS INTO W CNTRL
OK...
...THERE IS A MDT RISK OF SVR TSTMS FROM WRN OK INTO NEB AND IA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM NW TX NWD INTO SRN MN AND
WRN IL...
...SYNOPSIS...
A LARGE UPPER TROUGH WILL EXIST OVER THE WRN U.S. WITH UPPER LOW
CENTER NEAR THE FOUR CORNERS AREA AT 00Z...THEN CONTINUING INTO THE
CNTRL PLAINS BY SUN MORNING. AROUND THE BASE OF THIS TROUGH...A
MIDLEVEL JET CORE IN EXCESS OF 100 KT WILL BE NOSING INTO THE OK/TX
PANHANDLE BY 00Z...TIGHTENING FURTHER AS THE UPPER LOW ROTATES NEWD
ACROSS KS AND NEB. THIS BROAD BELT OF SWLY FLOW ALOFT WILL CREATE
FAVORABLE SHEAR FOR SEVERE WEATHER OVER A LARGE PART OF THE PLAINS.
AT THE SURFACE...A LOW WILL DEEPEN DURING THE DAY OVER ERN CO INTO
SWRN NEB...WITH THE 00Z DRYLINE POSITION ROUGHLY FROM CNTRL NEB NEAR
THE LOW SWD ACROSS KS AND INTO WRN OK AND NW TX. DURING THE
AFTERNOON AND EVENING...A WARM FRONT WILL EXTEND FROM THE LOW NEWD
ACROSS SERN SD INTO SRN MN.
SLY LOW LEVEL FLOW IN ANTICIPATION OF THE UPPER TROUGH WILL MAINTAIN
FAVORABLE MOISTURE TRAJECTORIES...WITH A NARROW AXIS OF MID 60S F
BOUNDARY LAYER DEWPOINTS EXTENDING FROM CNTRL TX ACROSS OK AND INTO
SRN KS AT 00Z. DEWPOINTS NEAR 60 F WILL BE POSSIBLE AS FAR N AS THE
WARM FRONT. COMBINED WITH COOL TEMPERATURES ALOFT...AMPLE
INSTABILITY WILL BE PRESENT FOR SEVERE STORMS FROM TX TO NEB.
...CNTRL NEB INTO WRN IA...
A STRONG SLY LOW LEVEL JET WILL HELP FORCE MORNING RAIN AND STORMS
OVER MUCH OF THE AREA...AND WILL ALSO ALLOW FOR DESTABILIZATION
DURING THE DAY BEHIND THIS INITIAL ACTIVITY. WITH THE SURFACE LOW
DEEPENING JUST TO THE W...AND A BROAD WARM FRONT AND/OR OUTFLOWS IN
PLACE...LOW LEVEL WINDS WILL REMAIN BACKED AND RH LEVELS SHOULD
REMAIN RELATIVELY SHELTERED AS WELL...PROVIDING A FAVORABLE AREA FOR
STRONG TORNADOES. CELLS WOULD LIKELY FORM OVER WRN SECTIONS OF THE
HIGH RISK AREA WHERE HEATING WILL STEEPEN LOW LEVEL LAPSE
RATES...THEN WOULD PROCEED RAPIDLY NEWD WITH AN INCREASING TORNADO
THREAT. VERY LARGE HAIL WILL ALSO BE LIKELY. THE NRN EXTENT OF THE
TORNADO THREAT WILL DEPEND ON THE ACTUAL LOCATION OF THE PRIMARY
BOUNDARIES.
...CNTRL KS...WRN AND CNTRL OK...NWRN TX...
SUBSTANTIAL UNCERTAINLY EXISTS IN REGARD TO STORM COVERAGE ALONG THE
DRYLINE DURING THE DAY FROM KS INTO OK AND NW TX. HOWEVER...HIGH END
SEVERE POTENTIAL EXISTS AND WILL MAINTAIN CATEGORICAL HIGH.
LOW CLOUDS AND SCATTERED SHOWERS ARE EXPECTED EARLY ON SAT...WITH
ONLY SLIGHT CAPPING IN PLACE EARLY. BREAKS IN THE CLOUDS AND HEATING
SHOULD QUICKLY ERODE MOST INHIBITION BY AFTERNOON...WHEN WITH
MODERATE INSTABILITY DEVELOPING WITH MUCAPE GENERALLY 2000-2500
J/KG.
STRONG HEATING AND STEEPENING OF LOW LEVEL LAPSE RATES WILL OCCUR
ALONG AND W OF THE DRYLINE. HOWEVER...CONVERGENCE WILL BE RELATIVELY
WEAK...WHICH MAY ACTUALLY HELP KEEP STORMS DISCRETE. FAVORABLY
ORIENTED DEEP LAYER SHEAR ALONG THE DRYLINE...AS WELL AS VEERING AND
INCREASING WINDS WITH HEIGHT WILL STRONGLY FAVOR SUPERCELLS.
THERMODYNAMIC PROFILES SHOULD BE SUFFICIENT FOR VERY LARGE
HAIL...AND LOW LEVEL SHEAR WILL FAVOR TORNADOES AS WELL. LAPSE RATES
ALOFT ARE MARGINAL FOR TYPICAL PLAINS VIOLENT TORNADO DAYS...BUT
SHEAR PROFILES WOULD CERTAINLY FAVOR A FEW STRONG TORNADOES.
CURRENT THINKING IS FOR ISOLATED TORNADIC SUPERCELLS WITH VERY LARGE
HAIL TO FORM ALONG THE DRYLINE...AND TO PROCEED NEWD ACROSS THE HIGH
RISK AREA LATE AFTERNOON INTO THE EVENING. THEN...THE PACIFIC FRONT
WILL MOVE IN FROM THE W...LIKELY RESULTING IN A SQUALL LINE CAPABLE
OF DAMAGING WINDS WITH EMBEDDED AREAS OF ROTATION CAPABLE OF DAMAGE.
FARTHER S INTO TX...DAYTIME DRYLINE ACTIVITY IS LESS LIKELY...WITH
THE MAIN SEVERE THREAT COMING FROM THE OVERNIGHT SQUALL LINE WITH
DAMAGING WINDS AND PERHAPS TORNADOES WITH SUPERCELLS EMBEDDED WITHIN
THE LINE.
..JEWELL.. 04/13/2012
The map below indicates the likelihood of severe weather impacting within 25 miles of any point within a shaded area.
http://www.spc.noaa.gov/products/outlook/day2probotlk_1730_any.gif
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT FRI APR 13 2012
VALID 141200Z - 151200Z
...THERE IS A HIGH RISK OF SVR TSTMS OVER ERN NEB AND FAR WRN IA...
...THERE IS A HIGH RISK OF SVR TSTMS FROM S CNTRL KS INTO W CNTRL
OK...
...THERE IS A MDT RISK OF SVR TSTMS FROM WRN OK INTO NEB AND IA...
...THERE IS A SLGT RISK OF SVR TSTMS FROM NW TX NWD INTO SRN MN AND
WRN IL...
...SYNOPSIS...
A LARGE UPPER TROUGH WILL EXIST OVER THE WRN U.S. WITH UPPER LOW
CENTER NEAR THE FOUR CORNERS AREA AT 00Z...THEN CONTINUING INTO THE
CNTRL PLAINS BY SUN MORNING. AROUND THE BASE OF THIS TROUGH...A
MIDLEVEL JET CORE IN EXCESS OF 100 KT WILL BE NOSING INTO THE OK/TX
PANHANDLE BY 00Z...TIGHTENING FURTHER AS THE UPPER LOW ROTATES NEWD
ACROSS KS AND NEB. THIS BROAD BELT OF SWLY FLOW ALOFT WILL CREATE
FAVORABLE SHEAR FOR SEVERE WEATHER OVER A LARGE PART OF THE PLAINS.
AT THE SURFACE...A LOW WILL DEEPEN DURING THE DAY OVER ERN CO INTO
SWRN NEB...WITH THE 00Z DRYLINE POSITION ROUGHLY FROM CNTRL NEB NEAR
THE LOW SWD ACROSS KS AND INTO WRN OK AND NW TX. DURING THE
AFTERNOON AND EVENING...A WARM FRONT WILL EXTEND FROM THE LOW NEWD
ACROSS SERN SD INTO SRN MN.
SLY LOW LEVEL FLOW IN ANTICIPATION OF THE UPPER TROUGH WILL MAINTAIN
FAVORABLE MOISTURE TRAJECTORIES...WITH A NARROW AXIS OF MID 60S F
BOUNDARY LAYER DEWPOINTS EXTENDING FROM CNTRL TX ACROSS OK AND INTO
SRN KS AT 00Z. DEWPOINTS NEAR 60 F WILL BE POSSIBLE AS FAR N AS THE
WARM FRONT. COMBINED WITH COOL TEMPERATURES ALOFT...AMPLE
INSTABILITY WILL BE PRESENT FOR SEVERE STORMS FROM TX TO NEB.
...CNTRL NEB INTO WRN IA...
A STRONG SLY LOW LEVEL JET WILL HELP FORCE MORNING RAIN AND STORMS
OVER MUCH OF THE AREA...AND WILL ALSO ALLOW FOR DESTABILIZATION
DURING THE DAY BEHIND THIS INITIAL ACTIVITY. WITH THE SURFACE LOW
DEEPENING JUST TO THE W...AND A BROAD WARM FRONT AND/OR OUTFLOWS IN
PLACE...LOW LEVEL WINDS WILL REMAIN BACKED AND RH LEVELS SHOULD
REMAIN RELATIVELY SHELTERED AS WELL...PROVIDING A FAVORABLE AREA FOR
STRONG TORNADOES. CELLS WOULD LIKELY FORM OVER WRN SECTIONS OF THE
HIGH RISK AREA WHERE HEATING WILL STEEPEN LOW LEVEL LAPSE
RATES...THEN WOULD PROCEED RAPIDLY NEWD WITH AN INCREASING TORNADO
THREAT. VERY LARGE HAIL WILL ALSO BE LIKELY. THE NRN EXTENT OF THE
TORNADO THREAT WILL DEPEND ON THE ACTUAL LOCATION OF THE PRIMARY
BOUNDARIES.
...CNTRL KS...WRN AND CNTRL OK...NWRN TX...
SUBSTANTIAL UNCERTAINLY EXISTS IN REGARD TO STORM COVERAGE ALONG THE
DRYLINE DURING THE DAY FROM KS INTO OK AND NW TX. HOWEVER...HIGH END
SEVERE POTENTIAL EXISTS AND WILL MAINTAIN CATEGORICAL HIGH.
LOW CLOUDS AND SCATTERED SHOWERS ARE EXPECTED EARLY ON SAT...WITH
ONLY SLIGHT CAPPING IN PLACE EARLY. BREAKS IN THE CLOUDS AND HEATING
SHOULD QUICKLY ERODE MOST INHIBITION BY AFTERNOON...WHEN WITH
MODERATE INSTABILITY DEVELOPING WITH MUCAPE GENERALLY 2000-2500
J/KG.
STRONG HEATING AND STEEPENING OF LOW LEVEL LAPSE RATES WILL OCCUR
ALONG AND W OF THE DRYLINE. HOWEVER...CONVERGENCE WILL BE RELATIVELY
WEAK...WHICH MAY ACTUALLY HELP KEEP STORMS DISCRETE. FAVORABLY
ORIENTED DEEP LAYER SHEAR ALONG THE DRYLINE...AS WELL AS VEERING AND
INCREASING WINDS WITH HEIGHT WILL STRONGLY FAVOR SUPERCELLS.
THERMODYNAMIC PROFILES SHOULD BE SUFFICIENT FOR VERY LARGE
HAIL...AND LOW LEVEL SHEAR WILL FAVOR TORNADOES AS WELL. LAPSE RATES
ALOFT ARE MARGINAL FOR TYPICAL PLAINS VIOLENT TORNADO DAYS...BUT
SHEAR PROFILES WOULD CERTAINLY FAVOR A FEW STRONG TORNADOES.
CURRENT THINKING IS FOR ISOLATED TORNADIC SUPERCELLS WITH VERY LARGE
HAIL TO FORM ALONG THE DRYLINE...AND TO PROCEED NEWD ACROSS THE HIGH
RISK AREA LATE AFTERNOON INTO THE EVENING. THEN...THE PACIFIC FRONT
WILL MOVE IN FROM THE W...LIKELY RESULTING IN A SQUALL LINE CAPABLE
OF DAMAGING WINDS WITH EMBEDDED AREAS OF ROTATION CAPABLE OF DAMAGE.
FARTHER S INTO TX...DAYTIME DRYLINE ACTIVITY IS LESS LIKELY...WITH
THE MAIN SEVERE THREAT COMING FROM THE OVERNIGHT SQUALL LINE WITH
DAMAGING WINDS AND PERHAPS TORNADOES WITH SUPERCELLS EMBEDDED WITHIN
THE LINE.
..JEWELL.. 04/13/2012