[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 120800
SWOMCD
SPC MCD 120800
KYZ000-INZ000-TNZ000-ALZ000-ILZ000-MSZ000-MOZ000-ARZ000-121300-

Mesoscale Discussion 0020
NWS Storm Prediction Center Norman OK
0200 AM CST Fri Jan 12 2018

Areas affected...Southwest IN...southeast IL...western
KY...southeast MO...western TN...extreme eastern AR...northern
MS...and extreme northwest AL

Concerning...Freezing rain

Valid 120800Z - 121300Z

SUMMARY...Rain will change to freezing rain (rates up to 0.10
inch/hour) across the discussion area, as surface temperatures fall
below 32 F with the passage of a sharp cold front.  Higher freezing
rain rates (around 0.20 inch/hour) will be possible with showers,
with freezing rain persisting the longest across the Mid-South
(northern MS into southwest TN).  Sleet should become the dominant
precipitation type between 09-12Z across the rest of the discussion
area.

DISCUSSION...Trends in surface analyses indicated a sharp cold will
continue to advance to the east across the lower OH/TN/MS Valleys
during the rest of the overnight to the early morning.  Given the
structure of this front, the vertical-thermodynamic profile in the
lower troposphere will have sub-freezing temperatures below 900 mb
with the frontal passage, and a warm nose persisting between 700-900
mb per trends in upstream raobs and forecast soundings.  This will
result in ongoing rain changing to freezing rain within 1-2 hours in
the wake of the cold front.  Strong height falls and DPVA attendant
to a progressive shortwave trough taking on a negative tilt across
the lower MS/TN Valleys will sustain the swath of precipitation and
showers developing and spreading from southwest to northeast through
at least 12-13Z.

Meanwhile, recent trends across the western extent of the
precipitation shield in parts of southeast MO and southern IL
indicated a reduction of the warm nose, such that sleet has become
the predominant precipitation type.  Given the continued potential
for embedded convection, the areas that change to sleet should have
rates sufficient for accumulation, as the vertical-thermodynamic
profile cools.

..Peters.. 01/12/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LMK...OHX...IND...HUN...PAH...MEG...JAN...LZK...

LAT...LON   34178838 33929036 33439110 33839155 34459125 34459125
            36828951 38608758 38458645 38338557 38358501 37228608
            36598666 34728765 34178838
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