[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 201740
SWOMCD
SPC MCD 201739 
TNZ000-ALZ000-MSZ000-201945-

MESOSCALE DISCUSSION 2057
NWS STORM PREDICTION CENTER NORMAN OK
1239 PM CDT FRI AUG 20 2004

AREAS AFFECTED...PORTIONS NERN MS...NRN AL...MIDDLE TN

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 201739Z - 201945Z

THERE IS INCREASING CONCERN FOR SEVERE TSTM POTENTIAL ACROSS THIS
REGION SFC-BASED CONVECTION CONTINUES TO EXPAND IN COVERAGE AND
STRENGTHEN OVER NEXT 2-3 HOURS.  BEST JUXTAPOSITION OF VERTICAL
SHEAR AND INSTABILITY SHOULD BE FROM NERN MS ENEWD ACROSS EXTREME
NRN AL AND SRN-MIDDLE TN.

SFC ANALYSIS SHOWS OUTFLOW BOUNDARY FROM EARLIER CONVECTIVE CLUSTER
EXTENDS FROM NEAR TYS WSWWD ACROSS SRN TN TO ROUGHLY 20 SE MKL.  AIR
MASS ALONG AND S OF THIS BOUNDARY HAS BECOME FAVORABLY UNSTABLE AND
VIRTUALLY UNCAPPED...WITH 70S F SFC DEW POINTS CONTRIBUTING TO
MLCAPES 1500-2000 J/KG.  VERTICAL SHEAR SHOULD BE MAXIMIZED ALONG
AND JUST N OF OUTFLOW BOUNDARY...WHERE SFC-BASED INSTABILITY SHOULD
DEVELOP GIVEN CONTINUED HEATING NEXT 2-3 HOURS.  REGION IS LOCATED
UNDER ENHANCED BELT OF MIDLEVEL SWLY FLOW -- I.E. 30-40 KT PER
REGIONAL VWP DATA.  THIS ALONG WITH MORE SLY COMPONENT TO SFC FLOW
NEAR BOUNDARY CONTRIBUTES TO 100-200 J/KG SRH IN LOWEST 1 KM
LAYER...BASED ON RUC FCST SOUNDINGS AND ON INTERPOLATIONS BETWEEN
VWPS AT BNA AND IN NRN AL.  DEEP-LAYER SHEAR IS MARGINAL FOR
SUPERCELLS AT 25-35 KT BUT BOUNDARY INTERACTIONS MAY ENHANCE THREAT
ON SMALL SCALES.  ALSO...LINE SEGMENTS AND BOWS MAY FORM WITH
DAMAGING GUSTS POSSIBLE.

..EDWARDS.. 08/20/2004

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

ATTN...WFO...MRX...OHX...BMX...HUN...MEG...JAN...

33458963 35138850 35868808 36048667 35758511 35418532
34998567 34138650 33538792 33338854 33258933 

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