Apr 29, 2013 2000 UTC Day 1 Convective Outlook
Updated: Mon Apr 29 19:54:34 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130429 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130429 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20130429 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20130429 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 32,081 2,008,539 Des Moines, IA...Cedar Rapids, IA...Platteville, WI...Tripoli, IA...
   SPC AC 291951
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0251 PM CDT MON APR 29 2013
   
   VALID 292000Z - 301200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF IA AND ADJACENT
   AREAS...
   
   ...DISCUSSION...
   THE OVERALL FORECAST CURRENTLY APPEARS ON TRACK...THOUGH A FEW MINOR
   TWEAKS HAVE BEEN INCLUDED THIS FORECAST.  IN THE SOUTHEAST...5%
   HAIL/WIND PROBABILITY HAS BEEN EXPANDED NWD FROM FL TO INCLUDE THE
   GA/SC COASTAL AREAS.  HERE...FAIRLY WIDESPREAD STORMS HAVE DEVELOPED
   WITHIN AN ENVIRONMENT FEATURING 500 TO 1500 J/KG MIXED-LAYER CAPE. 
   GIVEN AMPLE BACKGROUND SHEAR FOR MULTICELL ORGANIZATION...AN
   OCCASIONAL HAIL/WIND REPORT REACHING SEVERE CRITERIA WILL REMAIN
   POSSIBLE OVER THE NEXT FEW HOURS.
   
   FARTHER W OVER S TX...5% WIND/HAIL PROBABILITIES HAVE BEEN EXPANDED
   INTO THE MIDDLE TX COASTAL PLAIN...WITH 2% TORNADO PROBABILITY ALSO
   ADDED TO THIS AREA.  WITH A MOIST/MODESTLY UNSTABLE AIRMASS IN PLACE
   IN COMBINATION WITH MID-LEVEL FLOW SUPPORTIVE OF SOME UPDRAFT
   ORGANIZATION/WEAK ROTATION...A NWD EXPANSION OF PROBABILITIES AHEAD
   OF THE WEAK UPPER CIRCULATION CENTER INVOF DRT APPEARS JUSTIFIED.
   
   OTHERWISE...ISOLATED STORM DEVELOPMENT REMAINS POSSIBLE ACROSS THE
   IA VICINITY LATER THIS AFTERNOON/EVENING...WITH NO APPRECIABLE
   CHANGES REQUIRED IN THIS AREA.
   
   ..GOSS.. 04/29/2013
   
   .PREV DISCUSSION... /ISSUED 1122 AM CDT MON APR 29 2013/
   
   ...IA...
   WATER VAPOR LOOPS SHOW A FAST-MOVING SHORTWAVE TROUGH OVER WESTERN
   NEB.  THIS FEATURE WILL TRACK EASTWARD ACROSS THE NORTHERN/CENTRAL
   PLAINS TODAY AND HELP TO INITIATE SCATTERED THUNDERSTORMS ALONG A
   COLD FRONT OVER IA THIS EVENING.  12Z MODEL SOLUTIONS ARE SHOWING
   MORE CONSISTENCY IN TIMING AND LOCATION OF INITIATION OVER SOUTHWEST
   IA AROUND DUSK...WITH STORMS BUILDING NORTHEASTWARD THROUGH THE
   EVENING HOURS.  VERTICAL SHEAR PROFILES WILL SUPPORT SUPERCELLS
   CAPABLE OF LARGE HAIL AND DAMAGING WINDS.
   
   ...KS/MO/NEB...
   CONSIDERABLE UNCERTAINTY REMAINS REGARDING THE SOUTHWEST EXTENT OF
   CONVECTIVE INITIATION THIS EVENING.  FEW MODEL SOLUTIONS INDICATE
   STORMS FARTHER SOUTHWEST THAN THE MO RIVER THIS EVENING.  ALSO...
   SEVERAL MODELS APPEARS TO CONTINUE TO SUFFER FROM OVER-FORECASTED
   LOW LEVEL MOISTURE CONTENT.  NAM SOLUTIONS SHOW DEWPOINTS CLIMBING
   INTO THE MID/UPPER 60S BY LATE AFTERNOON OVER WESTERN MO.  IT IS
   BELIEVED THAT THOSE VALUES ARE 5-10 DEGREES TOO WARM.  THE LESSENED
   MOISTURE COULD POTENTIALLY INCREASE CAP STRENGTH...RAISE LCL
   HEIGHTS...AND DECREASE INITIATION POTENTIAL.  FOR THESE
   REASONS...HAVE MAINTAINED ONLY LOW SEVERE PROBS AS FAR SOUTHWEST AS
   CNK.  IN THE EVENT THAT STORMS CAN FORM...LARGE HAIL AND DAMAGING
   WINDS WOULD BE A CONCERN.
   
   ...DEEP SOUTH TX...
   LOW LEVEL MOISTURE IS RETURNING ACROSS DEEP SOUTH TX WITH DEWPOINTS
   NEAR 70F.  WATER VAPOR LOOPS SHOW A COMPACT UPPER SHORTWAVE TROUGH
   NEAR DRT WHICH MAY AFFECT THE REGION AROUND PEAK HEATING.  IF THIS
   OCCURS...SCATTERED STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE. 
   LOW LEVEL SHEAR IS WEAK...BUT SUFFICIENT DEEP LAYER SHEAR WOULD
   PROMOTE SUPERCELL STRUCTURES CAPABLE OF HAIL AND LOCALLY DAMAGING
   WINDS.
   
   ...FL...
   SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF THE FL PENINSULA
   THIS AFTERNOON AND EARLY EVENING.  A COMBINATION OF STRONG DAYTIME
   HEATING...COOL TEMPERATURES ALOFT...AND SUFFICIENT MOISTURE WILL
   RESULT IN ROBUST UPDRAFTS CAPABLE OF LOCALLY DAMAGING WINDS AND
   HAIL.
   
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