[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 100202
SWOMCD
SPC MCD 100202
TNZ000-KYZ000-MOZ000-ARZ000-MSZ000-100300-

MESOSCALE DISCUSSION 2143
NWS STORM PREDICTION CENTER NORMAN OK
0802 PM CST SUN DEC 09 2012

AREAS AFFECTED...ERN AR THROUGH WRN TN AND SWRN KY

CONCERNING...TORNADO WATCH 677...

VALID 100202Z - 100300Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 677 CONTINUES.

SUMMARY...TORNADO WATCH 677 IS SCHEDULED TO EXPIRE AT 03Z. THE
TORNADO THREAT IS EXPECTED TO GRADUALLY DECREASE THROUGH
EVENING...BUT A NON ZERO TORNADO OR SEVERE THREAT WILL PERSIST
THROUGH 05Z FROM ERN AR INTO WRN TN. AS A RESULT...DEPENDING ON
CONVECTIVE TRENDS...WW 677 COULD BE LOCALLY EXTENDED IN TIME AND
SPACE TO INCLUDE A PORTION OF WRN TN. SPC WILL CONTACT AFFECTED
OFFICES SOON TO DISCUSS THE COURSE OF ACTION REGARDING THE
EXPIRATION OF WW 677.

DISCUSSION...STORMS HAVE EVOLVED INTO A PREDOMINANT LINEAR MODE FROM
SWRN KY THROUGH ERN AR. TRENDS IN CONVECTIVE MODE...A STABILIZING
BOUNDARY LAYER...INCREASINGLY MARGINAL INSTABILITY...AND A TENDENCY
FOR THE LLJ TO GRADUALLY SHIFT EAST OF THE SFC MOIST AXIS SUGGEST
THE TORNADO THREAT SHOULD GRADUALLY DECREASE WITH TIME.
HOWEVER...LATEST VWP DATA FROM MEMPHIS STILL SHOW STRONG LOW LEVEL
SHEAR WITH 0-1 KM STORM RELATIVE HELICITY AROUND 250 M2/S2. GIVEN
THE FAVORABLE SHEAR ENVIRONMENT...EMBEDDED SUPERCELLS AND A TORNADO
OR TWO CANNOT BE COMPLETELY RULED OUT NEXT 2-3 HOURS AS ACTIVITY
CONTINUES THROUGH THE REMAINDER OF THE WEAK INSTABILITY AXIS.

OTHERWISE...STORMS DEVELOPING FARTHER EAST WITHIN WARM ADVECTION
REGIME OVER WRN TN ARE MORE DISCRETE IN CHARACTER...BUT ARE WITHIN A
WEAK INSTABILITY ENVIRONMENT AND APPEAR TO BE AT LEAST SLIGHTLY
ELEVATED.

..DIAL.. 12/10/2012

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

ATTN...WFO...PAH...MEG...LZK...

LAT...LON   34319237 35709026 36828848 36148845 35138934 34989022
            34239099 34319237



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