000
ACUS11 KWNS 060840
SWOMCD
SPC MCD 060839
KYZ000-INZ000-ILZ000-061315-

MESOSCALE DISCUSSION 2063
NWS STORM PREDICTION CENTER NORMAN OK
0239 AM CST FRI DEC 06 2013

AREAS AFFECTED...PORTIONS OF WRN KY...SRN INDIANA...SRN IL

CONCERNING...WINTER MIXED PRECIPITATION

VALID 060839Z - 061315Z

SUMMARY...WINTER MIXED PRECIPITATION WILL CONTINUE THROUGH THE
PRE-DAWN HOURS ACROSS THE LOWER/MIDDLE OHIO VALLEY REGION.

DISCUSSION...THE ONGOING SHIELD OF WIDESPREAD PRECIPITATION FROM THE
CONFLUENCE OF THE OH AND MS RIVERS NEWD TO NEAR CINCINNATI IS LIKELY
LINKED TO ASCENT ENCOURAGED BY A SUBTLE PERTURBATION EMBEDDED WITHIN
THE EXTENSIVE SW/NE-ORIENTED...ELEVATED WARM CONVEYOR STRUCTURE
OVERLYING THE REGION. LZK 2-2.5-KM VWP DATA SUGGESTS VEERING OF THE
FLOW WITHIN THIS LAYER IN THE 0330-0530 UTC TIME FRAME...AND THIS
FEATURE IS PROBABLY ENHANCING WINTER MIXED PRECIP ACROSS THE MCD
AREA AT PRESENT. IN THE WAKE OF THE PERTURBATION...MINOR SUBSIDENCE
MAY YIELD A TEMPORARY LESSENING OF THE COVERAGE AND INTENSITY OF
PRECIPITATION FROM SW TO NE AFTER 0930Z...THOUGH AT LEAST SCATTERED
LIGHT TO MODERATE PRECIP SHOULD CONTINUE AREA-WIDE DURING THE
PRE-DAWN HOURS.

SFC OBSERVATIONS PLACE THE 32F ISOTHERM RUNNING FROM JUST S OF
CINCINNATI TO NEAR LOUISVILLE TO NEAR DYERSBURG TN. A MODEST COLD
ADVECTION REGIME ANALYZED AT THE SFC AND WET BULB EFFECTS IN THE SFC
LAYER WILL HAVE A TENDENCY TO GRADUALLY EDGE THIS ISOTHERM SWD/SEWD
DURING THE NEXT SEVERAL HOURS. BEHIND THE FREEZING LINE...AREAS OF
FREEZING RAIN AND SLEET WILL BE LIKELY OWING TO COMPLETE/PARTIAL
MELTING OF HYDROMETEORS WITHIN THE 850-700-MB LAYER. THE LOUISVILLE
KY GOES SOUNDING SAMPLES TEMPS AROUND 2-4C IN THIS LAYER...WHICH
WILL LIKELY MAINTAIN THE MIXED PRECIPITATION MODE. COOLING ALOFT
WITH NWWD DISPLACEMENT ACROSS THE MCD AREA WILL SUPPORT A
PREDOMINANCE OF SLEET AND SNOW WITH NWWD DISPLACEMENT FROM THE OHIO
RIVER...WHILE FREEZING RAIN REMAINS MORE LIKELY IN CLOSER PROXIMITY
TO THE FREEZING LINE. THESE CONDITIONS ARE AFFIRMED BY RECENT
OBSERVATIONS FROM THE NSSL PRECIPITATION IDENTIFICATION NEAR THE
GROUND /PING/ PROJECT. LITTLE SUBSTANTIAL CHANGE TO THE OVERALL
THERMODYNAMIC STRATIFICATION SHOULD MAINTAIN A SIMILAR SPATIAL
PRECIP TYPE DISTRIBUTION THROUGH THE PRE-DAWN HOURS.

FREEZING RAIN RATES OF 0.05-0.10 INCH PER HOUR WILL BE
POSSIBLE...WITH THE GREATEST POTENTIAL FOR THE MOST SUBSTANTIAL
ICING EXISTING ONE OR TWO COUNTIES EITHER SIDE OF THE OHIO RIVER.
SLEET ACCUMULATIONS WILL ALSO BE POSSIBLE...WITH RATES POTENTIALLY
REACHING AROUND ONE-QUARTER INCH PER HOUR.

..COHEN.. 12/06/2013

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ILN...LMK...IND...PAH...

LAT...LON   36688875 37098917 37588897 38168776 38788606 39088514
            39018449 38398470 37238695 36688875