MESO: Mesoscale Discussion 2017

ACUS11 KWNS 012241
SWOMCD
SPC MCD 012240
GAZ000-TNZ000-ALZ000-020015-

MESOSCALE DISCUSSION 2017
NWS STORM PREDICTION CENTER NORMAN OK
0540 PM CDT MON OCT 01 2012

AREAS AFFECTED...PARTS OF MIDDLE TN...NRN AL...AND NRN GA

CONCERNING...TORNADO WATCH 658...

VALID 012240Z - 020015Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 658 CONTINUES.

SUMMARY...RISK FOR ISOLATED TORNADOES CONTINUES LATE THIS
AFTERNOON/EARLY EVENING...MAINLY NEAR SURFACE FRONT ACROSS NORTH
GEORGIA...AND ACROSS PARTS OF MIDDLE/EASTERN TENNESSEE. THE NEED
FOR A NEW WATCH IS NOT ANTICIPATED TO THE NORTH...ACROSS
KENTUCKY...PROBABLY NOT TO THE EAST...ACROSS EASTERN TENNESSEE...BUT
TRENDS WILL CONTINUE BE MONITORED.

DISCUSSION...IN THE WARM SECTOR OF AN OCCLUDING SURFACE LOW
MIGRATING NORTHEASTWARD INTO MIDDLE TENNESSEE...LOW-LEVEL SHEAR
SUPPORTIVE OF POTENTIAL FOR SIGNIFICANT UPDRAFT ROTATION HAS BECOME
CONFINED TO A CORRIDOR ACROSS WEST CENTRAL/NORTHWEST
GEORGIA...INCLUDING THE ATLANTA METRO AREA. OTHERWISE...SHEAR
BENEATH 40+ KT SOUTHERLY 850 MB FLOW IS GENERALLY MAXIMIZED TO THE
COOL SIDE OF THE QUASI-STATIONARY FRONT ASSOCIATED WITH THE
LINGERING COLD WEDGE TO THE SOUTHEAST OF THE SOUTHERN
APPALACHIANS...WHERE TORNADIC POTENTIAL REMAINS UNCLEAR DUE TO WEAK
TO STABLE NEAR SURFACE LAPSE RATES.

MEANWHILE...SUBSTANTIVE THUNDERSTORM ACTIVITY GENERALLY REMAINS
CONFINED TO A CLUSTER JUST NORTHEAST OF THE SURFACE LOW...AIDED BY
MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION NOW SPREADING NORTHWARD
ACROSS MIDDLE TENNESSEE...TO THE EAST AND SOUTHEAST OF NASHVILLE.
THIS MAY BE BASED WITHIN A NARROWING TONGUE OF BOUNDARY LAYER BASED
INSTABILITY...WITH AT LEAST SOME TORNADIC POTENTIAL CONTINUING
ANOTHER COUPLE OF HOURS...BEFORE FORCING WEAKENS/SPREADS NORTHWARD
INTO THE LOWER OHIO VALLEY...AND THE BOUNDARY LAYER STABILIZES DUE
TO WEAK COLD ADVECTION AND BOUNDARY LAYER COOLING.

..KERR.. 10/01/2012

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

ATTN...WFO...CAE...GSP...MRX...FFC...OHX...BMX...HUN...

LAT...LON 36418537 35788493 34828472 34518410 34208302 33768244
33318364 33378439 32628502 32588554 34358572 35728622
36378634 36418537

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