Surface Low developing
Posted by JAC on 12/23/2009, 2:05 pm






MESOSCALE DISCUSSION 2270
  NWS STORM PREDICTION CENTER NORMAN OK
  1221 PM CST WED DEC 23 2009
 
  AREAS AFFECTED...ERN NEB...S/CNTRL IA...NRN IL...FAR SRN WI/MN
 
  CONCERNING...FREEZING RAIN
 
  VALID 231821Z - 232215Z
 
  FREEZING RAIN WITH RATES NEAR 0.05 INCH AN HOUR WILL CONTINUE TO
  SLOWLY SHIFT NWD WITH TIME...INITIALLY AFFECTING AREAS NEAR CHICAGO
  WWD THROUGH DAVENPORT AND INTO OMAHA.
 
  WV IMAGERY REFLECTS A SHORT WAVE TROUGH ROTATING THROUGH CNTRL KS
  AHEAD OF A LARGER TROUGH NOW MOVING EWD THROUGH E CNTRL NM...LEADING
  TO FAVORABLE VERTICAL MOTION SUPPORTING AN ONGOING BAND OF FREEZING
  RAIN ACROSS PORTIONS OF IL/IA/NEB. SURFACE PRESSURE FALLS NEAR 1
  MB/2 HR ARE OCCURRING AHEAD OF THIS UPPER DISTURBANCE...MAINLY
  ACROSS CNTRL IA/NRN MO...INDICATING THE SURFACE LOW ANALYZED NEAR
  SERN KS IS BEGINNING TO DEVELOP NWD/NEWD WITH TIME. 17Z ANALYSIS
  REFLECTS THAT THE FREEZING LINE HAS BEGUN TO SHIFT NWD AS THIS
  OCCURS...AND AS STRONG WARM ADVECTION SLOWLY WARMS TEMPERATURES BY A
  FEW DEGREES. VAD WIND PROFILE DATA FROM CHICAGO WWD INTO DAVENPORT
  AND OMAHA SHOW STRONG WARM ADVECTION/VEERING WINDS IN THE LOWEST
  2000 FT. THIS WARM LAYER/ADVECTION JUST ABOVE THE SURFACE WILL
  CONTINUE TO SUPPORT FREEZING RAIN WHERE SURFACE TEMPERATURES ARE
  NEAR OR BELOW FREEZING...AS GROUND TEMPERATURES REMAIN COLD. 0.75
  INCH PWAT OBSERVED ON GOES SATELLITE PWAT IMAGERY REFLECTS AMPLE
  MOISTURE TO ASSIST IN ACCUMULATION RATES OF NEAR 0.05 INCH AN HOUR
  OR GREATER.
 
  ..HURLBUT.. 12/23/2009
 
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Big Storm for Central CONUS - JAC, 12/23/2009, 7:48 am
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