Moving into the Piedmont
Posted by JAC on 1/29/2010, 9:38 pm


MESOSCALE DISCUSSION 0088
  NWS STORM PREDICTION CENTER NORMAN OK
  0806 PM CST FRI JAN 29 2010
 
  AREAS AFFECTED...ERN TN / FAR NRN GA / UPSTATE SC / WRN NC AND PARTS
  OF THE NC PIEDMONT
 
  CONCERNING...WINTER MIXED PRECIPITATION
 
  VALID 300206Z - 300600Z
 
  INCREASING FROZEN PRECIP RATES ARE EXPECTED THIS EVENING AND
  ESPECIALLY INTO THE LATE NIGHT HOURS ACROSS THE SRN APPALACHIANS AND
  THE CAROLINA PIEDMONT VICINITY.  SNOWFALL RATES OVER THE HIGHER
  TERRAIN WILL PROBABLY REACH 1 INCH/HR THRU MIDNIGHT AND INCREASE
  THEREAFTER...POTENTIALLY NEARING 2 INCHES/HR IN LOCALIZED AREAS.  A
  PLETHORA OF SLEET/FREEZING RAIN WILL BEGIN TO YIELD SIGNIFICANT
  ICING ACCUMULATIONS WITH FREEZING RAIN RATES EXCEEDING 0.10 INCH/HR
  OVER SRN PORTIONS OF THE DISCUSSION AREA BY 06-09Z.
 
  CLOSED UPPER LOW OVER THE SRN PLAINS THIS EVENING WILL OPEN AND
  BEGIN TO SLIDE EWD TOWARDS THE LOWER MS VALLEY.  AS THIS OCCURS A
  LOW LEVEL CYCLONE NEAR THE MOUTH OF THE MS WILL MOVE NEWD INTO CNTRL
  AL...AND THIS WILL AID IN DRAWING GREATER MOISTURE NEWD /I.E. PRECIP
  WATER VALUES IN EXCESS OF ONE INCH PER COMPOSITE 00Z BMX-FFC RAOB/
  OVER A LOW LEVEL COLD AIR DOME E OF THE SMOKIES.  AS THIS
  OCCURS...THE COUPLING OF AN UPSTREAM AND DOWNSTREAM UPPER SPEED
  MAXIMA WILL FOCUS THE LEFT FRONT QUADRANT OF AN INTENSIFYING
  SUPTROPICAL JET OVER THE NRN GULF COAST STATES WITH THE RIGHT REAR
  QUADRANT OF A MID-ATLANTIC/NERN US UPPER JET...OVER THE REGION.
  THIS WILL FAVOR VIGOROUS LARGE SCALE ASCENT OVER THE SRN
  APPALACHIANS/PIEDMONT LATE THIS EVENING AND TOWARDS DAYBREAK
  SATURDAY.
 
  STRONG LOW LEVEL WAA THIS EVENING HAS RESULTED IN SURFACE TEMPS
  GRADUALLY WARMING ACROSS NRN AL/SRN MIDDLE TN THE PAST FEW
  HOURS...WHEREAS WET BULB COOLING IS CONTRIBUTING TO DECREASING
  SURFACE TEMPS ACROSS NC/SC.  00Z GSO RAOB AND AREA FORECAST
  SOUNDINGS E OF THE MTNS INITIALLY SHOW A DEEP ISOTHERMAL LAYER.
  HOWEVER...AS STRONG LOW LEVEL WAA FOCUSES ON THE REGION...THE H85-H7
  LAYER WILL WARM AOA 0 DEG C FAVORING A TRANSITION FROM PRIMARILY
  SNOW TO SLEET/FREEZING RAIN GENERALLY S OF I-40 /INCLUDING THE
  SMOKIES/ BY 09Z.  THE HIGHER ELEVATIONS ARE LIKELY TO EXPERIENCE
  APPRECIABLE SNOWFALL RATES FURTHER N OVER NWRN NC AS LARGE SCALE
  ASCENT AND UPSLOPE LEAD TO 1-2 INCH/HR RATES.  LATEST MODEL GUIDANCE
  SUGGESTS LIQUID EQUIVALENT SLEET/FREEZING RAIN RATES WILL GRADUALLY
  INCREASE THROUGH 09Z WITH 0.10 TO 0.15 INCH/HR POSSIBLE.
 
  ..SMITH.. 01/30/2010
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Major Winter Storm: OK to VA - JAC, 1/28/2010, 7:04 am
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