Another Rough Day for SD & NE Today
Posted by JAC on 5/24/2010, 10:12 am




DAY 1 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  0744 AM CDT MON MAY 24 2010
 
  VALID 241300Z - 251200Z
 
  ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF WESTERN
  NEBRASKA....MUCH OF SOUTH DAKOTA...AND PARTS OF NORTH DAKOTA...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
  FROM ND AND MN SWD TO WEST TX...
 
  ...A SIGNIFICANT SEVERE WEATHER EPISODE APPEARS INCREASINGLY LIKELY
  ACROSS PARTS OF THE CENTRAL AND NORTHERN GREAT PLAINS TODAY...
 
  ...THUNDERSTORMS DEVELOPING ACROSS THESE AREAS THIS AFTERNOON WILL
  HAVE STRONG POTENTIAL TO PRODUCE TORNADOES...LARGE/DAMAGING
  HAIL...AND DESTRUCTIVE WINDS...
 
  ...SYNOPSIS...
  MORNING WATER VAPOR SATELLITE IMAGERY SHOWS A POTENT SHORT WAVE
  TROUGH OVER THE FOUR CORNERS AREA PIVOTING THROUGH THE BASE OF A
  LARGER SCALE TROUGH SYSTEM THAT HAS DOMINATED THE WRN STATES FOR
  SEVERAL DAYS. MODEL GUIDANCE IS VERY CONSISTENT WITH THE TRACK AND
  EVOLUTION OF THIS DISTURBANCE...TAKING THE SHORT WAVE AND ASSOCIATED
  75-80KT MID LEVEL JET STREAK RAPIDLY NEWD TO THE NEB PANHANDLE AREA
  BY 00Z THIS EVENING...AND THEN CLOSING OFF A 500MB LOW OVER NERN MT
  BY TUESDAY MORNING. INTENSE FORCING FOR UPWARD VERTICAL MOTION WILL
  OVERSPREAD THE CNTRL AND NRN HIGH PLAINS FROM LATE MORNING THROUGH
  THIS EVENING AS THE UPPER TROUGH TAKES ON A PRONOUNCED NEGATIVE TILT
  AND DRIVES SIGNIFICANT SURFACE CYCLOGENESIS.
 
  RESULTING SURFACE LOW WILL DEEPEN RAPIDLY WHILE TRACKING ALMOST DUE
  NORTH FROM NERN CO TO WRN ND THROUGH THIS EVENING. WARM
  FRONT...CURRENTLY SITUATED FROM NEB PNHDL TO ERN SD TO CNTRL
  MN...WILL RETREAT QUICKLY NWD ACROSS THE REST OF SD AND INTO ND BY
  EVENING. TRAILING DRY LINE WILL MAKE SOME PROGRESS EAST FROM ERN
  CO/NM THIS MORNING...INTO KS AND NEB THROUGH THE AFTERNOON...AND
  THEN PERHAPS SURGING EWD ACROSS NEB AND NRN KS LATER TODAY AS THE
  LOW INTENSIFIES TO THE NORTH.
 
  FARTHER SOUTH...DRY LINE ADVANCE WILL LIKELY BE SLOWER DUE TO LARGE
  MERIDIONAL COMPONENT TO THE DEEP-LAYER FLOW.
 
  ELSEWHERE...A BLOCKING ANTICYCLONE WILL TAKE FORM FROM THE GREAT
  LAKES TO NEW ENGLAND. SOUTH OF THE CLOSED ANTICYCLONE AT 500MB...A
  WEAK SHORT WAVE TROUGH TRACKING SOUTH ACROSS THE CAROLINAS WILL
  BECOME ABSORBED BY LARGER DEEP-LAYER CYCLONIC CIRCULATION DRIFTING
  SHOREWARD FROM THE ATLANTIC.
 
  ...CNTRL AND NRN PLAINS...
  AN EXTENSIVE AND VERY MOIST WARM SECTOR AIR MASS LIES IN WAIT ACROSS
  MUCH OF THE GREAT PLAINS THIS MORNING AHEAD OF THE HIGH PLAINS DRY
  LINE AND SOUTH OF THE AFOREMENTIONED WARM FRONT. PW VALUES OF 1.00
  TO 1.50 INCHES EXIST ACROSS THE REGION AND LATEST RAOBS DEPICT STEEP
  MID LEVEL LAPSE RATES AND MINIMAL INHIBITION/CAPPING IN PLACE.
 
  INSTABILITY WILL INCREASE RAPIDLY ACROSS THE REGION WITH EARLY
  DAYTIME HEATING AND EXPECT SBCAPE OF 1500-3000 J/KG WITHIN THE NEXT
  FEW HOURS. GIVEN THIS DEGREE OF DESTABILIZATION AND QUICK ARRIVAL OF
  STRONG HEIGHT FALLS EMERGING FROM THE SRN CNTRL
  ROCKIES...THUNDERSTORM DEVELOPMENT IS LIKELY TO BE WELL UNDERWAY BY
  18Z FROM CO/KS BORDER TO SERN WY AND PERHAPS NEB. STORMS WILL
  CONTINUE TO INCREASE IN COVERAGE AND INTENSITY AS COMBINATION OF
  CONTINUED DIURNAL DESTABILIZATION AND STRONG ASCENT ACT TO OVERCOME
  ANY REMAINING INHIBITION.
 
  STRENGTHENING DEEP-LAYER SLY FLOW ACROSS MUCH OF THE WARM SECTOR
  WITH MEAN WIND NEARING 60KT WILL CONTRIBUTE TO FAST STORM MOTIONS
  AND SUFFICIENT SHEAR FOR NEWD TRACKING SUPERCELLS. MAGNITUDE OF
  INSTABILITY AND SHEAR AHEAD OF THE DRYLINE FROM KS TO SRN NEB
  SUGGESTS THAT TORNADOES AND LARGE HAIL WILL ACCOMPANY THIS
  CONVECTION. THERE IS SOME INDICATION THAT COLD FRONT/DRY LINE SURGE
  INTO NRN KS AND SRN NEB BY EVENING MAY RESULT IN THE EVENTUAL
  DEVELOPMENT OF A BOWING SQUALL LINE WITH SUBSEQUENT INCREASE IN WIND
  DAMAGE POTENTIAL.
 
  GREATER TORNADO THREAT SHOULD EVOLVE NEAR THE WARM FRONT AND
  DEEPENING SURFACE LOW...FROM NWRN NEB ACROSS SD THIS AFTERNOON.
  AGAIN...MAGNITUDE OF THE OVERALL FLOW WILL RESULT IN VERY FAST STORM
  MOTIONS AROUND 50KT. LOW LEVEL HODOGRAPH CURVATURE AND INTENSE SHEAR
  COINCIDENT WITH SUCH A VOLATILE AIR MASS AND FORCING STRONGLY
  SUGGEST TORNADIC SUPERCELLS AND VERY LARGE HAIL. EXPECT THIS
  POTENTIAL TO EXPAND NWD INTO ND BY EVENING AS THE SURFACE LOW AND
  WARM FRONT INTENSIFY. A COUPLE OF STRONG AND POSSIBLY LONG-TRACK
  TORNADOES APPEAR POSSIBLE GIVEN THE FORECAST SCENARIO.
 
  ...SRN PLAINS...
  STORM DEVELOPMENT FROM OK/TX PNHDLS SWD TO THE RIO GRANDE MAY BE
  MORE SCATTERED THAN FARTHER NORTH. HOWEVER...IT APPEARS THAT FORCING
  FOR ASCENT ACCOMPANYING THE SHORT WAVE TROUGH WILL AT LEAST BRUSH
  SOME OF THIS AREA AND...IN COMBINATION WITH DEEP MIXING ON THE DRY
  LINE...A FEW TO SEVERAL ROBUST THUNDERSTORMS SHOULD ERUPT THROUGH
  THE AFTERNOON. SUPERCELL HAIL/WIND AND TORNADO POTENTIAL WILL EXIST
  WITH STORMS PRIMARILY ACROSS THE PNHDLS AND ADJACENT PARTS OF TX/OK.
  FARTHER SOUTH...GENERALLY WEAKER FLOW SUGGESTS MORE ORGANIZED
  MULTICELL STORMS WITH HAIL AND ISOLATED DAMAGING WIND GUSTS.
 
  ..CARBIN/ROGERS.. 05/24/2010
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Another Rough Day for SD & NE Today - JAC, 5/24/2010, 10:12 am
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