Freezing Line
Posted by JAC on 1/26/2011, 8:51 am




MESOSCALE DISCUSSION 0047
  NWS STORM PREDICTION CENTER NORMAN OK
  0630 AM CST WED JAN 26 2011
 
  AREAS AFFECTED...PORTIONS ERN OH...NRN WV...NWRN VA...SWRN/S-CENTRAL
  PA...NWRN MD INCLUDING PANHANDLE.
 
  CONCERNING...WINTER MIXED PRECIPITATION
 
  VALID 261230Z - 261700Z
 
  POTENTIAL SHOULD INCREASE THROUGH 18Z FOR MIXTURE OF MDT/ISOLD HVY
  SNOW AND FREEZING RAIN...WITH LIQUID EQUIVALENT RATES .1-.2
  INCH/HOUR...INVOF OH RIVER VALLEY FROM PKB AREA NEWD INTO WRN PA.
 
  PRECIP FARTHER SW ACROSS ERN KY...FAR WRN VA AND SWRN WV HAS BEEN
  OCCURRING AS RAIN IN CONVEYOR OF ELEVATED LOW-LEVEL WAA JUXTAPOSED
  WITH INCREASING LARGE-SCALE DCVA/ASCENT IN MIDLEVELS. THIS TREND
  SHOULD CONTINUE...YIELDING MIX OF PRECIP TYPES AS IT CROSSES NEAR-
  TO BELOW-FREEZING SFC AIR.  12Z SFC MESOANALYSIS REVEALS THERMAL
  AXIS NEAR TRI...CRW...MGW...LBE LINE...BRACKETED BY FREEZING LINE
  NEAR LEX...ZZV...30 E HLG...20 N LBE THEN BECOMING ERRATIC DEPENDING
  ON ELEVATION SWD AND SEWD ACROSS NWRN WV AND NWRN MD/PANHANDLE
  REGION.  WEAK CAA AND DEEP-LAYER COOLING SHOULD HELP TO SHUNT
  FREEZING LINE SEWD OVER OH RIVER AREA THROUGH FORENOON HOURS...WITH
  LOWER DEW POINTS SUGGESTING SOME WET-BULB COOLING ALSO TO OCCUR OVER
  ERN OH/SRN PA/NRN WV PANHANDLE REGION.  ALTHOUGH MUCH OF OH VALLEY
  OF WV/SERN OH IS JUST ABOVE FREEZING ATTM...SNOW IS LIKELY DUE TO
  COLUMNAR COOLING ASSOCIATED WITH APCHG SWATH OF DEEP-LAYER
  ASCENT...AS EVIDENT IN TIME SERIES OF FCST SOUNDINGS.  UNTIL THAT
  OCCURS...TEMPS IN SHALLOW LAYER ABOVE SFC MAY REMAIN WARM ENOUGH TO
  SUPPORT THREAT FOR FREEZING RAIN INITIALLY.  FARTHER SW INVOF VA/WV
  BORDER AND WRN MD...SUPERFREEZING LAYER MAY BE MAINTAINED ABOVE
  SFC...WITH FREEZING RAIN BEING MORE DOMINANT THAN
  SNOW...TRANSITIONING MORE TOWARD SNOW NWD OVER PA.
 
  ..EDWARDS.. 01/26/2011
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Thursday 1/27 System - JAC, 1/24/2011, 7:32 am
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