Sep 22, 2015 1300 UTC Day 1 Convective Outlook
Updated: Tue Sep 22 12:50:08 UTC 2015 (20150922 1300Z Day 1 shapefile | 20150922 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150922 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 50,174 826,657 Sioux Falls, SD...Aberdeen, SD...Watertown, SD...Willmar, MN...Brookings, SD...
Probabilistic Tornado Graphic
20150922 1300 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.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20150922 1300 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.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20150922 1300 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.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 50,208 826,593 Sioux Falls, SD...Aberdeen, SD...Watertown, SD...Willmar, MN...Brookings, SD...
   SPC AC 221250

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0750 AM CDT TUE SEP 22 2015

   VALID 221300Z - 231200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS TONIGHT FOR ERN SD...SE
   ND...AND SW MN...

   ...SUMMARY...
   THUNDERSTORMS WILL DEVELOP TONIGHT ACROSS EASTERN SOUTH
   DAKOTA...SOUTHWESTERN MINNESOTA...AND SOUTHEASTERN NORTH
   DAKOTA...AND A FEW OF THE STORMS COULD PRODUCE MARGINALLY SEVERE
   HAIL.

   ...SYNOPSIS...
   IN THE WAKE OF A MIDLEVEL SHORTWAVE TROUGH OVER WRN ONTARIO...A
   SURFACE COLD FRONT WILL DRIFT SEWD ACROSS MN/IA/NEB AND THEN STALL
   NEAR THE NEB/KS BORDER THIS AFTERNOON.  THE BOUNDARY WILL THEN BEGIN
   TO MOVE NWD AS A WARM FRONT TONIGHT...IN RESPONSE TO WEAK LEE
   CYCLOGENESIS ACROSS THE CENTRAL/NRN HIGH PLAINS.  FARTHER S...A
   SERIES OF VORTICITY MAXIMA WILL MOVE NEWD FROM THE FOUR CORNERS TO
   THE CENTRAL HIGH PLAINS...ALONG WITH THE MIDLEVEL REMNANTS OF A
   TROPICAL MOISTURE PLUME EMANATING FROM THE ERN PACIFIC.

   SCATTERED THUNDERSTORMS ARE EXPECTED WITHIN THE MOISTURE PLUME
   ACROSS AZ/NM INTO SE CO TODAY...AND THE STORMS WILL PERSIST WELL
   INTO THE OVERNIGHT HOURS FROM ERN NM INTO ERN CO ALONG A WEAK LEE
   TROUGH AND IN THE ZONE OF ASCENT IMMEDIATELY DOWNSTREAM FROM THE
   SERIES OF VORTICITY MAXIMA.  OTHER SCATTERED THUNDERSTORMS ARE ALSO
   EXPECTED THIS AFTERNOON ACROSS S FL AND NEAR THE NE GULF COAST IN
   ASSOCIATION WITH A WEAK MIDLEVEL TROUGH. 

   ...ERN SD/SE ND/SW MN TONIGHT...
   A SEPARATE AREA OF ELEVATED THUNDERSTORMS WILL FORM AS EARLY AS LATE
   EVENING ACROSS NE NEB...WITH CONVECTION EXPECTED TO SPREAD NWD TO
   ERN SD/SW MN LATE TONIGHT.  THE CONVECTION WILL BE SUPPORTED BY WAA
   WITH A 30-40 KT LLJ...ON THE NE EDGE OF A REMNANT EML PLUME.  GIVEN
   BOUNDARY LAYER DEWPOINTS IN THE MID 60S IN THE PLAINS WARM SECTOR
   AND THE STEEP MIDLEVEL LAPSE RATES...MUCAPE WILL LIKELY REACH THE
   1500-2000 J/KG RANGE.  MEANWHILE...THE WAA REGIME AND WLY FLOW ALOFT
   WILL CONTRIBUTE TO SUFFICIENT EFFECTIVE BULK SHEAR FOR AT LEAST SOME
   RISK FOR ELEVATED SUPERCELLS.  GIVEN THE ELEVATED NATURE OF THE
   CONVECTION...ISOLATED LARGE HAIL WILL BE THE MAIN CONCERN TONIGHT.

   ..THOMPSON.. 09/22/2015

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