MCS thru upper MS-Valley this afternoon
Posted by JAC on 4/30/2010, 1:16 pm




...MID TO UPPER MS VALLEY/OZARKS...
  AN MCS CURRENTLY OVER NCNTRL MO WILL CONTINUE ENEWD INTO NCNTRL IL
  THIS AFTERNOON. A BROAD LOW-LEVEL JET SOUTH OF THE MCS ACROSS SCNTRL
  MO AND AR WILL RESULT IN STRONG MOISTURE ADVECTION. EXPECT MODERATE
  DESTABILIZATION ACROSS MUCH OF MO AND AR BY LATE THIS AFTERNOON AS
  SFC DEWPOINTS INCREASE INTO THE MID 60S F. MODEL FORECASTS ARE IN
  GOOD AGREEMENT...INITIATING NUMEROUS SFC-BASED THUNDERSTORMS ALONG
  THE WRN EDGE OF A WELL-DEVELOPED LOW-LEVEL JET FROM ECNTRL MO SSWWD
  INTO THE ARKLATEX. THE SHEAR ENVIRONMENT ALONG THIS CORRIDOR WITH
  0-6 KM SHEAR VALUES AROUND 50 KT SHOULD BE FAVORABLE FOR NUMEROUS
  SEVERE STORMS INCLUDING SUPERCELLS AND ORGANIZED BOWING
  LINE-SEGMENTS. A SIGNIFICANT SEVERE WEATHER EVENT WILL BE POSSIBLE
  ACROSS THE MODERATE RISK AREA THIS AFTERNOON THROUGH TONIGHT.
 
  THE CURRENT THINKING IS THAT THE LINE OF STORMS IN NW MO WILL BECOME
  INCREASINGLY ORGANIZED MOVING ENEWD ACROSS NRN MO AND SE IA THIS
  AFTERNOON INTO WRN IL EARLY THIS EVENING. A LINEAR MCS IS EXPECTED
  WITH THE STORMS MOVING INTO INCREASING LOW-LEVEL FLOW WHERE FORECAST
  SOUNDINGS SHOW ABOUT 50 KT AT 850 MB LATE THIS AFTERNOON. THIS ALONG
  WITH INCREASING LARGE-SCALE ASCENT DUE TO A UPPER-LEVEL SYSTEM TO
  THE NORTHWEST AND STRENGTHENING MID-LEVEL FLOW ASSOCIATED WITH THE
  RIGHT ENTRANCE REGION OF A 90 TO 100 KT MID-LEVEL JET WILL LIKELY
  PROMOTE STRONG LINEAR DEVELOPMENT FROM WRN IL SWD ACROSS ECNTRL MO
  EARLY THIS EVENING WHERE THE WIND DAMAGE THREAT SHOULD BECOME
  ENHANCED. TORNADOES AND LARGE HAIL WILL ALSO BE POSSIBLE ESPECIALLY
  WITH SUPERCELLS EMBEDDED IN THE LINE. A 45 PERCENT WIND DAMAGE
  PROBABILITY HAS BEEN ADDED FROM NRN IL SWWD ACROSS MOST OF ECNTRL
  MO.
 
  FURTHER SOUTH ACROSS SERN MO AND AR...MODEL FORECASTS ARE IN GOOD
  AGREEMENT...DEVELOPING NUMEROUS THUNDERSTORMS ALONG THE INSTABILITY
  AXIS. THE ENVIRONMENT SHOULD BE CHARACTERIZED BY MODERATE
  INSTABILITY AND STRONG DEEP LAYER SHEAR ESPECIALLY NORTH OF LITTLE
  ROCK WHERE INTENSE SUPERCELL DEVELOPMENT IS POSSIBLE BY EARLY THIS
  EVENING. IN NRN AR...LARGE-SCALE ASCENT IS FORECAST TO BE WEAKER
  THAN AREAS TO THE NORTH WHICH SHOULD HELP THE SUPERCELLS REMAIN
  DISCRETE BUT THE STORMS MAY BE MORE ISOLATED AS WELL. IN
  ADDITION...FORECAST SOUNDINGS ACROSS CNTRL AND NRN AR SHOW SFC WINDS
  BACKED TO THE SOUTH SOUTHEAST WHICH COMBINED WITH LOW LCL HEIGHTS
  COULD BE FAVORABLE FOR AN ISOLATED STRONG TORNADO. THE MORE DOMINANT
  SUPERCELL STRUCTURES SHOULD BE CAPABLE OF PRODUCING TORNADOES AND
  POSSIBLY VERY LARGE HAIL. THE THREAT FOR VERY LARGE HAIL SHOULD
  EXIST ACROSS AR SWWD INTO NE TX WHERE MODERATE TO STRONG INSTABILITY
  IS FORECAST.
 
  ..BROYLES/STOPPKOTTE.. 04/30/2010



PUBLIC SEVERE WEATHER OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1201 PM CDT FRI APR 30 2010
 
  ...SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF THE MID TO UPPER
  MISSISSIPPI VALLEY LATER TODAY AND TONIGHT...
 
  THE NWS STORM PREDICTION CENTER IN NORMAN OKLAHOMA IS FORECASTING
  THE DEVELOPMENT OF WIDESPREAD DAMAGING WINDS OVER PARTS OF THE MID
  TO UPPER MS VALLEY LATER TODAY AND TONIGHT.
 
  THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE
 
         FAR EASTERN IOWA
         ILLINOIS
         EASTERN AND SOUTH-CENTRAL MISSOURI
 
  ELSEWHERE...SEVERE STORMS ARE POSSIBLE FROM THE UPPER MIDWEST
  SOUTHWESTWARD ACROSS THE MID-MISSISSIPPI VALLEY...OZARKS INTO THE
  EASTERN PART OF THE SOUTHERN PLAINS.
 
  LOW-LEVEL MOISTURE WILL INCREASE NORTH NORTHEASTWARD ACROSS THE
  MODERATE RISK AREA IN RESPONSE TO A STRONG LOW-LEVEL JET OVER THE
  MID-MISSISSIPPI VALLEY. LIFT WILL ALSO INCREASE ACROSS THE MODERATE
  RISK AREA. THESE FACTORS ALONG WITH MODERATE INSTABILITY AND STRONG
  DEEP LAYER SHEAR PROFILES WILL BE SUPPORTIVE A WIDESPREAD SEVERE
  THREAT TODAY THROUGH TONIGHT. THE GREATEST POTENTIAL FOR WIND DAMAGE
  WILL EXIST FROM FAR EASTERN IOWA AND NORTHERN ILLINOIS SOUTH
  SOUTHWESTWARD ACROSS CENTRAL AND EASTERN MISSOURI. TORNADOES AND
  LARGE HAIL WILL ALSO BE POSSIBLE AS STORMS DEVELOP ALONG THIS
  CORRIDOR. IN ADDITION...A THREAT FOR ISOLATED STRONG TORNADOES MAY
  OCCUR IN EASTERN MISSOURI SOUTHWESTWARD TO CENTRAL ARKANSAS.
 
 
  ..BROYLES.. 04/30/2010






MESOSCALE DISCUSSION 0420
  NWS STORM PREDICTION CENTER NORMAN OK
  1201 PM CDT FRI APR 30 2010
 
  AREAS AFFECTED...SERN MN...NERN IA...WRN WI...WRN U.P. MI
 
  CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
 
  VALID 301701Z - 301730Z
 
  CONVECTION IS GRADUALLY INCREASING ALONG LEADING SURGE OF MOIST
  PLUME OVER IA.  AIRMASS IS DESTABILIZING DOWNSTREAM ACROSS MUCH OF
  NERN IA/SERN MN/WI WHERE DEW POINTS ARE RISING THROUGH THE 50S AND
  BOUNDARY LAYER IS WARMING/DEEPENING.  ALTHOUGH MUCH OF THE
  CONVECTION IS CURRENTLY ELEVATED OVER IA...IT APPEARS WITH CONTINUED
  HEATING THERE WILL BE A TENDENCY FOR UPDRAFTS TO ROOT INTO THE
  BOUNDARY LAYER...POSSIBLY NEAR-SFC BASED OVER THE NEXT FEW HOURS.
  ONE VERY FAST-MOVING NW-SE ORIENTED BOW-TYPE STRUCTURE IS RACING
  NEWD ACROSS GRUNDY/BLACK HAWK COUNTY IA AT ROUGHLY 60-65KT.
  DAMAGING WIND THREAT IS INCREASING WITH THESE BOW STRUCTURES AND A
  WW WILL BE ISSUED SOON.
 
  ..DARROW.. 04/30/2010
 



 




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Next possible severe event 4/29 to 4/30 Southern Plains - JAC, 4/26/2010, 12:42 pm
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