Apr-21-2005 1300 UTC Day 1 Convective Outlook
Updated: Thu Apr 21 14:52:10 UTC 2005
Categorical Graphic
20050421 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20050421 1300 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20050421 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20050421 1300 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 211243
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0743 AM CDT THU APR 21 2005
   
   VALID 211300Z - 221200Z
   
   THERE IS A MDT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM MDH 25
   NNE POF 35 WSW UNO 60 S HRO 25 NW TXK 15 SE DUA 50 E OKC 25 ESE PNC
   25 SW EMP 15 W MHK 25 WSW BIE 30 ESE LNK 45 W LWD 30 NW IRK 15 S UIN
   15 N ALN MDH.
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 30 E
   TPL 15 SW HDO 25 NE DRT 35 S SJT MWL 20 ESE OKC 10 NE ICT 10 W HSI
   25 W BUB 60 NE BUB 30 NE SUX 45 W ALO MMO 15 SSE LAF 45 N SDF 35 ESE
   OWB 30 ENE DYR 60 ENE LIT 25 SSE ELD 30 E TPL.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 SSE P07 50 ENE BGS
   30 W SPS 15 WNW OKC 30 SSW HUT MCK BFF 50 SW RAP 60 ESE REJ MBG RST
   10 NE BEH CMH ZZV MRB DOV 30 S ACY ...CONT... 35 E EWN 45 NW FLO 55
   SE MCN AQQ ...CONT... 30 NNE BVE 35 SE MCB 15 ESE HEZ 45 SW POE 35 N
   NIR LRD.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM EAT GEG 50 S S06 30
   NNE MQM 30 N JAC SLC 30 SSW ENV 4LW EUG 45 S OLM 45 SE SEA EAT.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 NNW SRQ VRB.
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF MO...ERN KS...ERN
   OK...NW AR AND A SMALL PART OF SE NEB...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER REMAINING PARTS OF THE
   CNTRL AND SRN PLNS...
   
   ...SYNOPSIS...
   MAJOR PATTERN CHANGE WILL OCCUR DURING THE NEXT 24-36 HRS AS STRONG
   IMPULSE NOW OVER NRN CO EJECTS E INTO THE CNTRL PLNS/MID MS VLY. AT
   THE SAME TIME...NRN STREAM SPEED MAX NOW OVER SASKATCHEWAN/MANITOBA 
   EXPECTED TO ACCELERATE SEWD...AMPLIFYING EXISTING TROUGH OVER THE
   GRT LKS.
   
   WHILE THE PLNS IMPULSE WILL LIKELY REMAIN VERY COMPACT...MID LEVEL
   W/WNWLY FLOW WILL NEVERTHELESS INCREASE SUBSTANTIALLY ACROSS MUCH OF
   THE CNTRL AND SRN PLNS AS LARGE SCALE PATTERN AMPLIFIES.  THIS WILL
   SERVE TO STRENGTHEN DEEP SHEAR OVER THE CNTRL U.S. THROUGH THE
   PERIOD...AND DRIVE COLD FRONT NOW OVER WRN KS E TO THE MID MS/LWR OH
   VLY REGION BY 12Z SATURDAY.  AT THE SAME TIME...SURFACE LOW NOW OVER
   N CNTRL KS SHOULD TRACK GENERALLY E ALONG WAVY WARM FRONT INTO CNTRL
   IL.
   
   ...LWR MO TO MID MS VLY...
   SEVERE THUNDERSTORMS EXPECTED TO DEVELOP BY EARLY AFTERNOON INVOF
   SURFACE LOW/TRIPLE POINT OVER SE NEB/NE KS AS DIURNAL HEATING
   FURTHER DESTABILIZES REGION OF LOW LEVEL MOISTURE INFLOW.  BOTH
   SATELLITE DATA AND MODEL GUIDANCE SUGGEST THAT MAIN AREA OF ASCENT
   ASSOCIATED WITH UPR IMPULSE WILL STILL BE W OF TRIPLE POINT AT THIS
   TIME.  RESULTING ABSENCE OF STRONG LINEAR FORCING...COUPLED WITH
   MODERATE /35-40 KT/ DEEP SWLY SHEAR AND STEEP MID LEVEL LAPSE
   RATES...SHOULD SUPPORT SUPERCELLS WITH A GOOD POTENTIAL FOR VERY
   LARGE HAIL /AVERAGE MLCAPE TO 2000 J PER KG/.
   
   THE STORMS SHOULD MOVE/DEVELOP ESE ALONG NEARLY STATIONARY WARM
   FRONT ACROSS NRN/CNTRL MO A BIT LATER IN THE DAY...WHERE ENHANCED
   LOW LEVEL VORTICITY INVOF BOUNDARY AND EXPECTED STORM MOTION ROUGHLY
   PARALLEL TO IT MAY PROMOTE LOW LEVEL MESOCYCLOGENESIS AND A FEW
   TORNADOES.  OTHER STRONG/SEVERE STORMS MAY DEVELOP IN POCKET OF
   SURFACE-BASED INSTABILITY AND CONVERGENCE NEAR OLD OUTFLOW BOUNDARY
   IN ERN MO BY EARLY AFTERNOON.  MERGING OF THIS ACTIVITY WITH THAT
   ARRIVING FROM THE WNW...ALONG WITH INCREASING LARGE SCALE
   ASCENT...WILL LIKELY LEAD TO CONSOLIDATION INTO SEVERAL CLUSTERS OF
   STORMS THAT WILL CARRY AN ATTENDANT THREAT FOR HAIL AND PERHAPS HIGH
   WIND E INTO IL TONIGHT.
   
   ...DRY LINE ERN KS/SW MO SWD INTO CNTRL AND NE TX...
   MORE WIDELY SCATTERED SUPERCELLS EXPECTED TO DEVELOP A BIT LATER IN
   THE DAY SWD ALONG DRY LINE INTO TX AS SURFACE HEATING OVERCOMES CAP
   NOW IN PLACE.  SATELLITE DATE SUGGEST THAT MUCH OF THIS CORRIDOR
   WILL INDEED EXPERIENCE STRONG HEATING. IN ADDITION... OUTFLOW FROM
   YESTERDAY'S DRY LINE ACTIVITY SEEMS TO BE CONFINED TO PARTS OF NRN
   OK/CNTRL KS.  COUPLED WITH INCREASING WLY FLOW ALOFT THAT WILL
   GRADUALLY LENGTHEN HODOGRAPHS AND KEEP DEEP SHEAR FAIRLY
   PERPENDICULAR TO DRY LINE...SETUP SHOULD SUPPORT A FEW LONG-LIVED
   SUPERCELLS.  FAIRLY MOIST BOUNDARY LAYER AND STEEP MID LEVEL LAPSE
   RATES WILL BE FAVORABLE FOR VERY LARGE HAIL AND POSSIBLY A COUPLE
   TORNADOES.
   
   ...VA/NC...
   A FEW STRONG DIURNAL STORMS MAY FORM IN ENVIRONMENT OF STEEP LOW TO
   MID LEVEL LAPSE RATES ALONG THE LEE SLOPES OF THE VA/NC
   MOUNTAINS...AND INVOF COLD FRONT/LEE TROUGH.  LIGHT TO MODERATE
   /20-25 KT/ LARGELY UNIDIRECTIONAL WNWLY MEAN FLOW MAY ALLOW FOR
   ORGANIZATION INTO SHORT BANDS...AND POSSIBLY A LIMITED THREAT FOR
   DAMAGING WIND AND MARGINALLY SEVERE HAIL.
   
   ..CORFIDI/TAYLOR.. 04/21/2005
   
   ...NOTICE...
   THE STATION RELATIVE POINTS IN THIS PRODUCT ARE NOW AVAILABLE
   SEPARATELY UNDER THE WMO HEADINGS WUUS01 PTSDY1...
   WUUS02 PTSDY2...WUUS03 PTSDY3.  THE INCLUSION OF POINTS
   IN THIS DISCUSSION WILL BE DISCONTINUED AFTER THE 2005
   CONVECTIVE SEASON.  A PUBLIC NOTIFICATION STATEMENT (PNS)
   WILL PROVIDE DETAILS ON THE TRANSITION.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z