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Mesoscale Discussion 80
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   MESOSCALE DISCUSSION 0080
   NWS STORM PREDICTION CENTER NORMAN OK
   0637 PM CST FRI FEB 20 2015

   AREAS AFFECTED...PORTIONS OF SRN/CNTRL/ERN MO...SRN IL...AND EXTREME
   WRN KY

   CONCERNING...WINTER MIXED PRECIPITATION 

   VALID 210037Z - 210630Z

   SUMMARY...AREAS OF FREEZING RAIN...POSSIBLY MIXED WITH SLEET...WILL
   CONTINUE TO EXPAND ACROSS THE AREA THIS EVENING INTO EARLY
   TONIGHT...WITH ICE ACCRETION RATES UPWARDS OF 0.05-0.10
   IN/HR...ESPECIALLY IN POCKETS OF CONVECTION.

   DISCUSSION...00Z REGIONAL WSR-88D MOSAIC AND ASOS/MPING REPORTS
   INDICATE AREAS OF FREEZING RAIN ARE BEGINNING TO SLOWLY EXPAND
   ACROSS THE OZARKS AND TO THE NORTHEAST. OVER THE NEXT SEVERAL
   HOURS...PCPN IS FORECAST TO CONTINUE TO INCREASE IN COVERAGE...AS
   ADIABATIC ASCENT/WARM AIR ADVECTION STRENGTHENS ON THE NOSE OF A
   60-KT LLJ /DEPICTED BY GROWING CYCLONICALLY LOOPED HODOGRAPHS IN
   FCST SOUNDING DATA/. ADDITIONALLY...23Z SFC OBSERVATIONS INDICATE
   PRES FALLS NEAR THE OH VALLEY OF AROUND 1 MB/HR...REFLECTING THE
   MASS-ASCENT RESPONSE FROM AN APPROACHING SHORTWAVE TROUGH ACROSS THE
   CENTRAL PLAINS...AS WELL AS INCREASING WAA ALOFT. FCST SOUNDING DATA
   INDICATE CONVECTIVE ELEMENTS/THUNDER ARE ALSO POSSIBLE...WITH WEAK
   ELEVATED BUOYANCY DEVELOPING THIS EVENING. UPSTREAM OBSERVATIONS
   /E.G. THE 17Z LMN SOUNDING AND CG LIGHTNING STRIKES ACROSS AR/
   SUPPORT THIS POTENTIAL...WITH STEEPER MID-LEVEL LAPSE RATES NOTED IN
   THE SOUNDING DATA. 

   THE AFOREMENTIONED STRENGTHENING WAA ALOFT WILL SUPPORT MAINLY FZRA
   ACROSS THE MCD AREA /AS EVIDENCED BY THE PROMINENT WARM NOSE ON THE
   00Z SGF SOUNDING/. HOWEVER...A DEEP ENOUGH SUB-FREEZING LAYER NEAR
   THE SFC WILL PROMOTE POCKETS OF ICE PELLETS AT TIMES /ESPECIALLY
   EARLIER THIS EVENING AND ACROSS NRN-ERN AREAS/. INDEED...MPING
   REPORTS AND DUAL-POL DATA /E.G. ZDR INDICATING POCKETS OF
   RE-FREEZING/ AGREE WITH THIS POTENTIAL. REGARDLESS...WITH A
   CONSIDERABLE INCREASE IN FORCING FOR ASCENT COMBINING WITH THE
   AFOREMENTIONED THERMODYNAMIC PROFILE...ICE ACCRETION RATES OF
   0.05-0.10 PER HR ARE FORECAST THIS EVENING...ESPECIALLY ACROSS
   PORTIONS OF THE OZARKS. THE HEAVIEST PCPN RATES WILL THEN SHIFT TO
   THE NORTH/EAST AFTER MIDNIGHT...AS ISENTROPIC ASCENT SUBSIDES ACROSS
   THE AREA.

   ..PICCA/EDWARDS.. 02/21/2015


   ATTN...WFO...PAH...ILX...LSX...SGF...EAX...

   LAT...LON   39369022 38638819 38038775 37258777 37148816 36918976
               36789181 36969343 37259382 37599391 38259385 38899335
               39269214 39369022 

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Page last modified: February 21, 2015
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