[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 160018
SWOMCD
SPC MCD 160018
VAZ000-TNZ000-KYZ000-INZ000-ILZ000-160415-

MESOSCALE DISCUSSION 2129
NWS STORM PREDICTION CENTER NORMAN OK
0618 PM CST WED DEC 15 2010

AREAS AFFECTED...PARTS OF SRN IL / SRN IND / WRN-CNTRL KY / NRN TN

CONCERNING...FREEZING RAIN

VALID 160018Z - 160415Z

WINTER MIXED PRECIPITATION PRIMARILY IN THE FORM OF FREEZING RAIN
EXCEPT FOR PORTIONS NEAR KENTUCKIANA AND N-CNTRL KY WHERE A MIX OF
PRECIP TYPES WILL BEGIN TO OCCUR LATE THIS EVENING INTO THE
OVERNIGHT HOURS.  HOURLY FREEZING RAIN RATES MAY APPROACH 0.05-0.10
INCH BY 06Z ACROSS PARTS OF CNTRL KY.

SURFACE ANALYSIS PLACES A CYCLONE OVER THE SRN PLAINS WITH HIGH
PRESSURE LOCATED ACROSS THE MIDDLE OH RIVER VALLEY.  AS THE SRN
PLAINS SURFACE LOW DEVELOPS NE TOWARDS THE LOWER OH VALLEY LATE
TONIGHT...A BROAD ZONE OF INCREASING ISENTROPIC LIFT /AIDED BY 50+
KT SWLY LLJ/ WILL HELP IN FOCUSING LARGE SCALE FORCING FOR ASCENT
ACROSS THE REGION ATOP A SLOW TO MODIFY COLD DOME.  SURFACE TEMPS
ACROSS THE REGION ARE GENERALLY IN THE MID 20S TO NEAR 30 DEG F WITH
DEWPOINTS 10-20 DEG F.  THIS WILL ALLOW WET BULB EFFECTS TO
INITIALLY COOL THE SURFACE BEFORE WARMING TEMPS OVER WRN TN ADVECT
NEWD INTO PORTIONS OF WRN KY AND PARTS OF MIDDLE TN LATE...LEADING
TO SOME CHANGEOVER FROM FREEZING RAIN TO RAIN.

AN INFLUX OF RICHER MOISTURE CHARACTERIZED BY PW VALUES 0.5-0.75
INCH IS NOW SPREADING INTO THE REGION.  00Z BNA RAOB SHOWS AN
APPRECIABLE WARM LAYER /4 DEG C AT 825 MB/ FAVORING FREEZING RAIN.
FORECAST SOUNDINGS SHOW THE LOW-MID LEVELS GRADUALLY COMING TO
SATURATION IN THE 02-04Z TIMEFRAME ACROSS KY AND ADJACENT STATES.
THIS WILL PROBABLY YIELD INITIALLY LIGHT FREEZING RAIN/SLEET RATES
THROUGH 03Z.  MODEL GUIDANCE INDICATES THAT SOME POTENTIAL EXISTS
FOR SLANTWISE CONVECTION ACROSS THE AREA...ESPECIALLY TOWARDS 06Z
AND THEREAFTER--ACTING TO ENHANCE PRECIP RATES.  THE HEAVIER RATES
/0.05-0.10 INCH PER HOUR/ ARE EXPECTED TO BEGIN TO DEVELOP IN THE
03-06Z PERIOD.

..SMITH.. 12/16/2010

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

ATTN...WFO...MRX...JKL...LMK...OHX...IND...PAH...ILX...LSX...

LAT...LON   35818424 36328667 37728950 38538960 39028904 39068774
            38158497 37058364 36298353 35818424


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