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Mesoscale Discussion 177
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   MESOSCALE DISCUSSION 0177
   NWS STORM PREDICTION CENTER NORMAN OK
   0350 PM CDT WED APR 01 2015

   AREAS AFFECTED...NRN KS...CNTRL/ERN NEB...FAR SERN SD...NWRN
   IA...SWRN MN

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 012050Z - 012245Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...THE POTENTIAL FOR WIDESPREAD TSTM INITIATION IS BEING
   MONITORED ALONG A COLD FRONT... WHICH MAY OCCUR WITHIN THE NEXT 1-2
   HRS. DESPITE A MARGINAL THERMODYNAMIC ENVIRONMENT...THE POTENTIAL
   WILL EXIST FOR STRONG-SVR WIND GUSTS AND INSTANCES OF LARGE HAIL.
   TRENDS ARE BEING MONITORED FOR A POSSIBLE WW.

   DISCUSSION...WEAK CU DEVELOPMENT HAS RECENTLY BEEN NOTED BENEATH
   SCATTERED MID-HIGH LEVEL CLOUDS ACROSS NERN NEB INTO SERN SD...ALONG
   A SEWD PROGRESSING COLD FRONT WHICH EXTENDS SWWD TO A SFC LOW OVER
   NWRN KS. A FEW LIGHTNING STRIKES HAVE ALSO BEEN NOTED IN ASSOCIATION
   WITH CONVECTION DEVELOPING NEAR A WEAK SFC LOW OVER NWRN KS. TRENDS
   IN SFC OBS SHOW WEAK LOW-LEVEL MOIST ADVECTION BEING OFFSET BY DEEP
   BOUNDARY-LAYER MIXING...WITH DEW POINTS ONLY IN THE UPPER 30S TO MID
   40S F AHEAD OF THE COLD FRONT. ALSO OF NOTE...MODEL GUIDANCE HAS HAD
   DIFFICULTY ACCURATELY DEPICTING THE MAGNITUDE OF BOUNDARY-LAYER
   MOISTURE...WITH THE NAM AND GFS TOO MOIST...AND THE RAP TOO DRY. 

   LATEST THINKING IS THAT WIDESPREAD CONVECTIVE INITIATION COULD OCCUR
   BY 23Z AS WEAK ASCENT/MIDLEVEL HEIGHT FALLS ALONG THE SRN PERIPHERY
   OF A NRN ROCKIES/PLAINS SHORTWAVE OVERSPREADS THE AREA. DESPITE
   MEAGER BOUNDARY-LAYER MOISTURE...VERY STEEP MIDLEVEL LAPSE RATES
   /OVER 8 C/KM/ ARE STILL YIELDING MLCAPE VALUES OF 500-800 J/KG.
   GIVEN THE HIGH-BASED NATURE OF CONVECTION...COMBINED WITH 20-30 KT
   OF AMBIENT LOW-LEVEL FLOW...STRONG TO SVR WIND GUSTS SHOULD BE THE
   PRIMARY THREAT. HAIL MAY ALSO ACCOMPANY MORE ROBUST DISCRETE
   DEVELOPMENT INITIALLY...BUT THE DEGREE OF LOW-LEVEL FRONTAL FORCING
   SHOULD EVENTUALLY RESULT IN CONSOLIDATION INTO A MORE LINEAR MODE. 

   TRENDS WILL CONTINUE TO BE MONITORED FOR SIGNS OF INCREASING TSTM
   DEVELOPMENT...WHICH COULD PROMPT ISSUANCE OF A WW...POSSIBLY BY 23Z.

   ..ROGERS/HART.. 04/01/2015


   ATTN...WFO...MPX...DMX...FSD...OAX...TOP...GID...LBF...DDC...
   GLD...

   LAT...LON   43979413 41689524 40039774 38920031 38730102 38890136
               39660060 41739857 43599668 44549630 44849559 44659496
               43979413 

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Page last modified: April 01, 2015
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