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Mesoscale Discussion 510
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   MESOSCALE DISCUSSION 0510
   NWS STORM PREDICTION CENTER NORMAN OK
   0228 PM CDT WED MAY 07 2014

   AREAS AFFECTED...ERN SOUTH DAKOTA...SWRN MINNESOTA AND ADJACENT NW
   IOWA

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 071928Z - 072130Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...THE RISK FOR AT LEAST MARGINALLY SEVERE HAIL MAY ACCOMPANY
   VIGOROUS STORMS ACROSS PARTS OF EASTERN SOUTH DAKOTA INTO WEST
   CENTRAL MINNESOTA DURING THE NEXT COUPLE OF HOURS.  STRONGER STORM
   DEVELOPMENT APPEARS POSSIBLE ACROSS NORTHWESTERN IOWA INTO
   SOUTHWESTERN MINNESOTA TOWARD THE 22-00Z TIME FRAME...WHEN A WATCH
   COULD BECOME NECESSARY.

   DISCUSSION...VERY WARM ELEVATED MIXED LAYER AIR ADVECTING NORTHEAST
   OF THE MID MISSOURI VALLEY IS CAPPING A POTENTIALLY UNSTABLE
   BOUNDARY LAYER ENVIRONMENT IN THE WARM SECTOR OF A REMNANT FRONTAL
   WAVE NEAR/SOUTH AND WEST OF THE SIOUX FALLS/SIOUX CITY AREA. 
   HOWEVER...ON THE EDGE OF STRONGER CAPPING...WITHIN THE 700 MB
   THERMAL GRADIENT ARCING ROUGHLY ALONG A LINE THROUGH MITCHELL SD/
   WATERTOWN SD AND ALEXANDRIA MN...VIGOROUS THUNDERSTORM DEVELOPMENT
   IS UNDERWAY.  THIS IS TO THE COOL SIDE OF THE SURFACE FRONTAL
   ZONE...BUT ELEVATED MOISTURE RETURN ON SOUTHERLY FLOW BENEATH STEEP
   MID-LEVEL LAPSE RATES IS CONTRIBUTING TO MODERATE CAPE.  AND
   VERTICAL SHEAR IN THE CLOUD BEARING LAYER IS STRONG...IN ASSOCIATION
   WITH A 50+ KT SOUTH SOUTHWESTERLY 500 MB JET STREAK NOSING
   NORTHEASTWARD ACROSS THE EASTERN DAKOTAS.

   ALTHOUGH AT LEAST A MARGINAL SEVERE HAIL THREAT PROBABLY ACCOMPANIES
   THIS CONVECTION...SUPPORTING LARGE-SCALE FORCING APPEARS TRANSIENT
   IN NATURE...AND IT REMAINS UNCLEAR HOW LONG CURRENT ACTIVITY WILL
   MAINTAIN INTENSITY.  AT LEAST SOMEWHAT MORE SUBSTANTIVE SEVERE
   WEATHER POTENTIAL MAY HOLD OFF UNTIL THE 22-00Z TIME FRAME...WHEN
   MODELS...INCLUDING THE RAPID REFRESH... SUGGEST ANOTHER SUBTLE
   NORTHEASTWARD PROGRESSING MID-LEVEL IMPULSE MAY CONTRIBUTE TO STORM
   DEVELOPMENT IN CLOSER PROXIMITY TO THE SURFACE FRONT...ACROSS PARTS
   OF NORTHWESTERN IOWA/SOUTHWESTERN MINNESOTA.

   ..KERR/HART.. 05/07/2014


   ATTN...WFO...MPX...DMX...FGF...FSD...ABR...

   LAT...LON   44609804 45879657 45779475 44909573 44099444 43069448
               43099586 43549806 44609804 

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Page last modified: May 07, 2014
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