SPC DAY-1 CONVECTIVE OUTLOOK

21 Jan 1999 - 05:51:23 UTC 
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ZCZC MKCSWODY1 000
ACUS1 KMKC 210551
MKC AC 210551

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 211200Z - 221200Z

THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
PARTS OF CENTRAL/EASTERN AR...NORTHEAST LA...NORTHERN MS...AND
WESTERN TN...TO THE RIGHT OF A LINE FROM ARG DYR 30 WNW MSL CBM 45
NE JAN MLU HOT ARG.

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM GLS
GGG PGO HRO MDH OWB BNA BHM MOB.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 45 E PSX TYR MKO SZL
PIA MIE CRW PSK SPA ATL PNS.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 WSW P28 CSM TCC
LVS ALS COS GCK 30 WSW P28.

STRONG UPPER JET MAX CURRENTLY OVER THE WESTERN STATES IS FORECAST
TO MOVE SOUTHEASTWARD INTO THE SOUTHERN ROCKIES BY THIS
AFTERNOON...WITH LARGE UPPER TROUGH RAPIDLY AMPLIFYING OVER THE
PLAINS. NOSE OF STRONG MID LEVEL WINDS WILL SPREAD INTO CENTRAL TX
BY 00Z...WITH SURFACE LOW DEEPENING OVER OK. SURFACE DRYLINE WILL
EXTEND SOUTHWARD ACROSS EAST TX...WITH WARM/HUMID AIRMASS ALREADY
IN PLACE TO THE EAST.

ISOLATED STRONG/SEVERE THUNDERSTORMS MAY BE ONGOING AT THE
BEGINNING OF THE PERIOD OVER SOUTHERN IL/WESTERN KY...WITH LARGE
HAIL BEING THE MAIN THREAT. THESE STORMS SHOULD SPREAD EASTWARD
ACROSS THE OH VALLEY DURING THE DAY IN REGION OF MODERATELY STRONG
WARM ADVECTION. HOWEVER...WEAKENING INSTABILITY WILL LIMIT
EASTWARD EXTENT OF SEVERE THREAT.

AIRMASS ALONG AND EAST OF DRYLINE OVER AR/LA WILL BE MODERATELY
UNSTABLE BY MID AFTERNOON WITH SURFACE-BASED CAPE VALUES OF 1500-
2000 J/KG. ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP IN THIS
AREA AND SPREAD RAPIDLY EAST-NORTHEASTWARD ACROSS WESTERN
TN/NORTHERN MS DURING THE EVENING. MODEL FORECAST SOUNDINGS SHOW
VERY STEEP MID LEVEL LAPSE RATES AND DRY AIR ALOFT...FAVORABLE FOR
LARGE HAIL AND DAMAGING WINDS. ALSO...STORM-RELATIVE HELICITY
/300-500 M2/S2/...MAGNITUDE OF DEEP LAYER SHEAR /SFC-6KM SHEAR OF
45-55 KNOTS/...AND STRENGTH OF MID LEVEL STORM-RELATIVE WINDS /20-
30 KNOTS/ INDICATE POTENTIAL FOR A FEW TORNADIC SUPERCELLS ACROSS
THE HIGH RISK AREA. GIVEN THE STRENGTH OF FORECAST SHEAR
MAGNITUDES AND THERMODYNAMIC PROFILES...ISOLATED SIGNIFICANT
TORNADOES ARE POSSIBLE TODAY OVER PARTS OF SOUTHEAST AR...NORTHEAST
LA...SOUTHWEST TN...AND NORTHERN AL.

ACTIVITY WILL LIKELY PERSIST THROUGHOUT THE NIGHT...SPREADING INTO
PORTIONS OF MIDDLE TN AND AL BY 22/12Z. DAMAGING WINDS AND HAIL
SHOULD BE THE MAIN THREAT BY THAT TIME.
 
..HART.. 01/21/99

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