[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 161510
SWOMCD
SPC MCD 161509
TNZ000-162015-

MESOSCALE DISCUSSION 0069
NWS STORM PREDICTION CENTER NORMAN OK
0909 AM CST MON FEB 16 2015

AREAS AFFECTED...A LARGE PART OF TN

CONCERNING...WINTER MIXED PRECIPITATION

VALID 161509Z - 162015Z

SUMMARY...FREEZING RAIN AND SLEET WILL CONTINUE SUPPORTING
SUBSTANTIAL ICING ACROSS MUCH OF TN INTO THE AFTERNOON...WITH THE
PRECIPITATION SPREADING EWD WITH TIME.

DISCUSSION...SFC OBSERVATIONS ARE INDICATING WIDESPREAD SLEET AND
FREEZING RAIN ASSOCIATED WITH A CONTINUOUS SHIELD OF PRECIPITATION
EXTENDING FROM THE MID-SOUTH REGION TO MIDDLE TN. WITH NQA AND OHX
VWPS DEPICTING NOTABLE VEERING OF WIND DIRECTION WITH HEIGHT IN THE
LOWER TROPOSPHERE...WAA IS STRONG ACROSS THE AREA. RELATED STRONG
ISENTROPIC ASCENT WILL CONTINUE IN PROXIMITY TO A LLJ THAT WILL
GRADUALLY SHIFT EWD INTO THE AFTERNOON...WITH THE
ASCENT/PRECIPITATION SPREADING TOWARD THE APPALACHIANS.

THE 12Z BNA RAOB SAMPLES AN ELEVATED WARM LAYER JUST ABOVE H85
SURMOUNTING DEEP SUB-FREEZING AIR...SUPPORTING SLEET.
HOWEVER...ELEVATED WAA-ENHANCED WARMING WILL ALSO HAVE A PROPENSITY
TO MELT DESCENDING HYDROMETEORS TO SUPPORT AREAS OF FREEZING RAIN
ACROSS THE REGION...AND LOCAL-AREA/UPSTREAM OBSERVATIONS SUGGEST
FREEZING RAIN RATES OF 0.05-0.10 INCH PER HOUR THIS MORNING. SLEET
ACCUMULATION RATES MAY REACH NEAR A QUARTER INCH PER HOUR.
SUBSTANTIAL ICING WILL LIKELY RESULT FROM THESE FREEZING RAIN/SLEET
RATES...ESPECIALLY IN ANY CONVECTIVE ELEMENTS.

SHORT-RANGE FORECAST SOUNDINGS DO INDICATE NEAR-SFC WARMING
SUPPORTING A TRANSITION TO PURE LIQUID RAIN ACROSS SRN PARTS OF
MIDDLE AND SERN TN THIS AFTERNOON. HOWEVER...OBSERVATIONS SHOW A
VERY DRY AIR MASS IN PLACE -- AS REPRESENTED BY SFC DEWPOINTS FROM
THE UPPER SINGLE DIGITS TO THE TEENS -- AND RELATED WET-BULB COOLING
MAY OFFSET SFC-LOW PRECEDING WAA AND VERY MODEST DIURNAL HEATING. AS
SUCH...IT IS POSSIBLE THAT FROZEN PRECIPITATION MAY PREDOMINATE
REGION-WIDE. ELSEWHERE...PRECIPITATION WILL BEGIN TAPERING OFF FROM
WEST TO EAST ACROSS PARTS OF THE MID-SOUTH BY MID-AFTERNOON...AS
LARGE-SCALE ASCENT SHIFTS EWD.

..COHEN.. 02/16/2015

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

ATTN...WFO...MRX...OHX...HUN...MEG...

LAT...LON   35768956 36248858 36548687 36538493 36498293 35798364
            35158521 35048822 35089005 35768956



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