[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 160858
SWOMCD
SPC MCD 160857
KYZ000-TNZ000-INZ000-ALZ000-ILZ000-MSZ000-MOZ000-ARZ000-OKZ000-KSZ000-161500-

MESOSCALE DISCUSSION 0067
NWS STORM PREDICTION CENTER NORMAN OK
0257 AM CST MON FEB 16 2015

AREAS AFFECTED...NERN OK/SRN MO/SRN IL/SRN INDIANA/WRN AND CENTRAL
KY/WRN AND MIDDLE TN/AR/NRN MS/NWRN AL

CONCERNING...WINTER MIXED PRECIPITATION

VALID 160857Z - 161500Z

SUMMARY...A WIDESPREAD AREA OF WINTRY PRECIPITATION -- INCLUDING
HEAVY SNOW ACROSS MO/SRN IL/SRN INDIANA AND KY...MIXED PHASES ACROSS
NRN AR/FAR SERN MO AND PARTS OF NRN TN...AND MAINLY FREEZING RAIN
ACROSS CENTRAL AND SRN AR/NRN MS/NWRN AL AND INTO SRN TN -- WILL
CONTINUE THROUGH THIS MORNING.  HEAVY SNOW ACCUMULATIONS ARE LIKELY
ACROSS NRN PORTIONS OF THE DISCUSSION AREA...WITH SUBSTANTIAL
FREEZING RAIN ACCUMULATIONS OVER SRN PORTIONS OF THE AREA.

DISCUSSION...A STRONG LOW-LEVEL BAROCLINIC ZONE CONTINUES TO TIGHTEN
ACROSS THE SRN PLAINS/MID MS/TN VALLEY REGION EARLY THIS MORNING.
THIS BAROCLINIC ZONE LIES AT THE INTERSECT OF SURFACE HIGH PRESSURE
AND AN ASSOCIATED POLAR/ARCTIC AIRMASS SPILLING SEWD OUT OF CANADA
INTO THE PLAINS/MIDWEST/NERN STATES...WHILE PRONOUNCED ADVECTION OF
HIGHER THETA-E LOW-LEVEL AIR CONTINUES ACROSS TX/THE LOWER MS
VALLEY/GULF COASTAL STATES.

THIS BACKGROUND SCENARIO IS UNFOLDING DUE TO A BRIEF TRANSITIONAL
STAGE OF THE ERN U.S. LONG-WAVE TROUGH...AS A STRONG/SMALLER-SCALE
TROUGH/LOW MOVES OUT OF THE NERN U.S. INTO THE CANADIAN MARITIMES
AND A SECOND/REINFORCING TROUGH DIGS SEWD OUT OF CANADA AND ACROSS
THE NRN INTERMOUNTAIN REGION.  BETWEEN THESE TWO SYSTEMS...A BRIEFLY
MORE ZONAL/WLY FLOW FIELD ALOFT IS MANIFESTING OVER THE S CENTRAL
AND SERN CONUS.

AS THE WRN TROUGHING DIGS SEWD...SURFACE CYCLOGENESIS OVER THE S
CENTRAL U.S. ALONG THE AFOREMENTIONED BAROCLINIC ZONE IS YIELDING A
ZONE OF STRONG WARM ADVECTION -- DRIVING THE ISENTROPIC ASCENT AND
RESULTING WINTRY PRECIPITATION EVENT THAT IS ONGOING.  WHILE
MIXED-PHASE PRECIPITATION IS INDICATED ACROSS A SIZABLE PORTION OF
THE DISCUSSION AREA ATTM -- IN PART DUE TO CONVECTIVE NATURE OF THE
PRECIPITATION...CURRENT THINKING IS THAT THE BAND OF HEAVIEST
SNOWFALL -- WITH RATES OF 1-2" PER HOUR -- WILL OCCUR FROM NERN OK
ENEWD ACROSS NWRN AR AND SRN MO...AND EWD INTO SRN IL/WRN KY.  WITH
TIME...EWD EXPANSION OF THE HEAVY SNOW BAND IS EXPECTED TO
CONTINUE...SPREADING INTO SRN INDIANA AND CENTRAL/WRN KY WITH TIME.

FARTHER S -- A ZONE OF MIXED-PHASE PRECIPITATION WILL PERSIST --
MAINLY ACROSS NRN AR AND PARTS OF WRN TN.  HOWEVER...A TRANSITION TO
PRIMARILY SNOW IS EXPECTED TO GRADUALLY OCCUR LATER THIS MORNING
OVER WRN PORTIONS OF THIS AREA...I.E. NWRN AR...AS THE EVOLVING
SURFACE LOW -- AND PRECEDING ZONE OF STRONGEST WARM ADVECTION --
SHIFTS EWD OUT OF TX AND ACROSS THE LOWER MS VALLEY WITH TIME.
ACROSS SRN PORTIONS OF THE AREA -- INCLUDING PARTS OF CENTRAL AND
SRN AR/NRN MS/NWRN AL AND SRN TN...SUBSTANTIAL FREEZING RAIN
ACCUMULATIONS ARE EXPECTED TO CONTINUE.  WHILE ERN PORTIONS OF THE
AFOREMENTIONED AREA -- I.E. NERN MS/NWRN AL/SRN MIDDLE TN -- REMAIN
ABOVE FREEZING...DEWPOINTS IN THE SINGLE DIGITS SUGGEST SUBSTANTIAL
WET-BULB COOLING IS LIKELY -- SUPPORTING THE EXPECTATION THAT
FREEZING RAIN WILL PREDOMINATE ACROSS THESE AREAS INTO THE
MID-MORNING HOURS.

..GOSS/CORFIDI.. 02/16/2015

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

ATTN...WFO...MRX...JKL...ILN...LMK...OHX...IND...BMX...HUN...
PAH...MEG...JAN...LSX...LZK...SGF...SHV...TSA...ICT...

LAT...LON   34869487 35689629 36409657 36999603 38139163 38328983
            38438435 38108318 37068337 35908535 34468682 33988864
            33759199 34229402 34869487



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