SPC DAY-1 CONVECTIVE OUTLOOK

08 Mar 1999 - 12:52:04 UTC 
disclaimer  "for information regarding the availability and timeliness of 
forecasts and products.

ZCZC MKCSWODY1 000
ACUS1 KMKC 081252
MKC AC 081252

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 081300Z - 091200Z

REF WW 75...VALID TIL 1800Z.

THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
PARTS OF EXTREME NORTHEAST TX...SOUTHERN AR...AND NORTHERN LA...TO
THE RIGHT OF A LINE FROM PBF GLH 55 WNW JAN HEZ ESF 55 S SHV 15 SW
GGG 25 ENE PRX 40 ESE PGO HOT PBF.

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM
25 SSW BPT ACT BWD 50 ENE ABI OKC TUL UMN UNO MKL HSV ANB TOI
20 ENE PNS.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM BLI SEA PDX MFR
60 NW UKI.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 SW GLS HOU CLL
50 NE JCT ABI LTS P28 CNK STJ UIN LUK 10 SE HTS AHN AQQ.

...OUTBREAK OF TORNADOES POSSIBLE TODAY OVER PARTS OF NORTHERN
LA/NORTHEAST TX/SOUTHERN AR...

LARGE PROGRESSIVE UPPER TROUGH OVER THE WESTERN STATES WILL MOVE
RAPIDLY EASTWARD TODAY INTO THE PLAINS AND MS VALLEY. WATER VAPOR
IMAGERY SHOWS TWO VORTICITY MAXIMA...ONE CURRENTLY OVER SOUTHEAST
CO AND A SECOND ALONG THE AZ/NM BORDER. THE FIRST SYSTEM IS
EXPECTED TO LIFT NORTHEASTWARD INTO THE MIDWEST STATES WHILE THE
OTHER FEATURE DRIVES EASTWARD ACROSS TX/OK AND INTO THE LOWER MS
VALLEY. THIS AREA WILL BE AT RISK OF SIGNIFICANT SEVERE
THUNDERSTORMS TODAY.

VERY STRONG SOUTHERLY LOW LEVEL JET /60-70 KT/ IS DEVELOPING ACROSS
CENTRAL TX AT THIS TIME. RAPID TRANSPORT OF GULF MOISTURE WILL
OCCUR THROUGH THE DAY INTO PARTS OF TX/OK/AR/LA. BY THIS
AFTERNOON...SURFACE DRYLINE IS EXPECTED TO EXTEND FROM LOW OVER
NORTHERN OK INTO EAST TX. WIDESPREAD CLOUD COVER WILL LIMIT
HEATING EAST OF DRYLINE...BUT SURFACE DEWPOINTS SHOULD RISE INTO
THE LOW 60S AS FAR NORTH AS SOUTHERN AR. RELATIVELY STEEP LAPSE
RATES AND LOW LEVEL DESTABILIZATION...ALONG WITH TEMPERATURES IN
THE MID 70S WEST OF DRYLINE...WILL RESULT IN AFTERNOON CAPE VALUES
OF 1500-2000 J/KG ACROSS THE ARKLATEX REGION.

AREA OF STRONG/SEVERE THUNDERSTORMS CURRENTLY OVER CENTRAL TX MAY
PERSIST THROUGH THE MORNING HOURS...WITH THREAT OF LARGE HAIL AND
DAMAGING WINDS. STORMS WILL HAVE A THREAT OF ISOLATED TORNADOES BY
LATE MORNING/EARLY AFTERNOON AS SURFACE-BASED INSTABILITY
INCREASES.

OTHER SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER
NORTHEAST TX/SOUTHEAST OK ALONG SURFACE DRYLINE BY MID AFTERNOON. 
EXTREMELY STRONG SHEAR PROFILES WILL BE PRESENT ACROSS THIS AREA
/SFC-6KM SHEAR EXCEEDING 60 KT AND 3KM HELICITY VALUES OF 600-900
M2/S2/ TO FAVOR RAPID DEVELOPMENT OF SUPERCELL STORMS. AREAL
COVERAGE OF INTENSE ACTIVITY WILL BE LIMITED ON THE NORTH/EAST/WEST
BY RATHER SMALL INSTABILITY AXIS...AND ON THE SOUTH BY AXIS OF
UPPER LEVEL JET. FORECAST CAPE VALUES ARE SLIGHTLY LOWER THAN
COMMONLY ASSOCIATED WITH TORNADO OUTBREAKS. HOWEVER...THE EXTREME
NATURE OF THE SHEAR PROFILES AND FAVORABLE TIMING OF SYSTEM LEND
SUFFICIENT CONFIDENCE IN FORECAST TO GO HIGH RISK OVER PARTS OF
SOUTHERN AR/EXTREME NORTHEAST TX...AND NORTHERN LA. A FEW STRONG
TORNADOES ARE POSSIBLE LATER TODAY OVER THE HIGH RISK AREA.

STORMS ARE EXPECTED TO SPREAD EASTWARD DURING THE EVENING INTO
PARTS OF TN/MS/AL. MORE STABLE SURFACE CONDITIONS SUGGEST A
DECREASED TORNADO THREAT IN THIS AREA. HOWEVER...ACTIVITY MAY
EVOLVE INTO SQUALL LINE PRODUCING DAMAGING WINDS AND HAIL.
 
..HART.. 03/08/99

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