SPC DAY-1 CONVECTIVE OUTLOOK

04 May 1999 - 12:23:47 UTC 
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ZCZC MKCSWODY1 000
ACUS1 KMKC 041223
MKC AC 041223

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 041300Z - 051200Z

REF WW NUMBER 0206...VALID TIL 01600Z
REF WW NUMBER 0207...VALID TIL 01600Z

THERE IS A HIGH RISK OF SVR TSTMS OVER PORTIONS NERN TX...SERN
OK...SWRN AR...AND NWRN LA...TO THE RIGHT OF A LINE FROM
50 NW POE 50 WNW LFK 55 ENE ACT 15 ENE DAL 25 S DUA 30 SSE MLC
15 S PGO 30 ESE HOT 10 S PBF 25 NE MLU 35 SW MLU 35 N POE
50 NW POE.

SURROUNDING THE HIGH RISK...THERE IS A MDT RISK OF SVR TSTMS OVER
ERN OK...MUCH OF AR...N-CENTRAL/NERN TX...NRN LA AND EXTREME NWR
MS...TO THE RIGHT OF A LINE FROM 10 NNE POE 45 N CLL ACT 15 SW FTW
30 WSW ADM 45 ENE OKC 30 W BVO 10 E BVO 25 ENE FYV 35 SW ARG 25 WSW
MEM 15 W GWO 30 N HEZ 10 WSW ESF 15 WSW ESF 10 NNE POE.

OUTSIDE THE MDT AND HIGH RISKS...THERE IS A SLGT RISK OF SVR TSTMS
TO THE RIGHT OF A LINE FROM 25 NW LCH 30 S AUS 25 W HDO 40 ENE DRT
50 NNE DRT 20 SSE SJT 45 W END P28 45 ENE DDC 60 WSW HLC 40 SW MCK
20 E LBF 50 WSW YKN 30 E 3SE 20 E DBQ 25 SSE MMO 35 SSW HUF 15 SSE
CKV 40 NE CBM 30 WNW LUL 30 NNE LFT 25 NW LCH.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 55 NNW ELO
15 ESE RHI 25 E SBN 40 ESE LUK 25 NNE TYS 30 SSE RMG 35 E BVE
...CONT... 40 SW GLS 55 NW LRD ...CONT... 20 WNW DRT 25 WSW LTS
35 ESE GAG 45 NE GAG 50 S DDC 25 WSW LBL 45 SW CAO 15 NW LVS
35 N 4SL 20 WSW MTJ 20 ENE VEL 50 E JAC 25 W COD 30 NE COD
25 W SHR 40 S SHR 30 ENE CPR 35 SE 4DG 25 NNW BFF 30 SSE CDR
50 SW PHP 45 N PHP 30 NE Y22 80 NE ISN.

REGIONAL OUTBREAK OF TORNADIC SUPERCELLS POSSIBLE FROM N-CENTRAL TX
EWD ACROSS NRN LA AND NEWD TOWARD OZARKS. SOME STRONG-VIOLENT
TORNADOES POSSIBLE...ESPECIALLY INVOF HIGH RISK.

--- SYNOPSIS --- 
VIGOROUS MIDDLE-UPPER LEVEL SHORTWAVE TROUGH -- NOW EVIDENT ON
MOISTURE CHANNEL IMAGERY FROM 4-CORNERS CIRCULATION SEWD ACROSS ERN
NM...IS FORECAST TO MOVE EWD THEN NEWD ACROSS SRN/CENTRAL PLAINS
DURING PERIOD...WITH MIDDLE LEVEL LOW CENTERED OVER ERN NEB BY
05/12Z. ASSOCIATED DEEP LOW LEVEL CYCLONE IS DEVELOPING OVER WRN
KS S OF NEB LOW -- SHOULD MOVE NEWD ACROSS KS TOWARD NW MO BY END
OF PERIOD. NOCTURNAL WWD SLOSHING OF DRYLINE REVERSED BY 10Z THIS
MORNING WITH GREATER INFLUENCE OF LARGE-SCALE FORCING...AND 35-40
KT WLYS OBSERVED ACROSS ERN NM/FAR W TX. THIS DRY SURGE SHOULD
PROGRESS ENEWD ACROSS MUCH OF CENTRAL/NRN TX AND WRN OK DURING
DAY...WITH SHARPENING DRYLINE SIMILAR TO 9Z RUC2 GUIDANCE.

...SEVERE THUNDERSTORM FORECAST DISCUSSION...

--- SRN PLAINS TO LOWER MS VALLEY ---
FOR MORE DETAILS REGARDING ONGOING/NOWCAST SEVERE WEATHER THREAT
OVER TX/OK...REF WWS 206/207 AND THEIR STATUS REPORTS.

ISALLOBARIC FORCING ASSOCIATED WITH CENTRAL PLAINS CYCLONE SHOULD
RESULT IN STRONG LOW LEVEL WARM/MOIST ADVECTION ACROSS MUCH OF
REGION THROUGHOUT THE DAY. THOUGH THIS SHOULD BE MITIGATED ON
MESOSCALE BY CONVECTIVE OUTFLOWS...LARGE-SCALE FORCING IS STRONG
ENOUGH SUCH THAT AIR MASSES SHOULD RECOVER QUICKLY BEHIND MOST
MORNING/EARLY AFTERNOON CONVECTIVE CLUSTERS. DEEP LAYER OF RICH
LOW LEVEL MOISTURE IN SHV RAOB. SURFACE DEW POINTS NOW IN 60S OVER
REGION SHOULD INCREASE INTO UPPER 60S/LOW 70S..WHICH COMBINE WITH
INSOLATION TO YIELD MLCAPE TO NEAR 3000 J/KG AND SBCAPE ABOVE 4000
J/KG.

FORECAST SOUNDINGS AND MODIFIED 12Z RAOBS INDICATE BRN SHEAR AOA
100 J/KG LIKELY OVER MUCH OF AREA. ALSO...200-400 J/KG SR HELICITY
AND NO NOTABLE LOW-MID LEVEL SR FLOW WEAKNESSES AOB 20 KT ALREADY
OBSERVED IN FWD SOUNDING...AND SHOULD REPRESENT MUCH OF HIGH RISK
REGION TODAY. JUXTAPOSITION OF SEVERAL VERY FAVORABLE FORECAST
PARAMETERS COMBINING TO INDICATE THREAT OF CYCLIC/TORNADIC
SUPERCELLS. DEVELOPMENT EXPECTED IN SEVERAL AREAS -- INVOF
DRYLINE...AHEAD OF DRYLINE IN ZONES OF MESOSCALE MASS
CONVERGENCE...AND NEAR OUTFLOWS. IN ADDITION TO TORNADO THREAT...
DAMAGING HAIL AND SEVERE GUSTS ARE ALSO LIKELY. SEVERE SQUALL LINE
SHOULD EVOLVE FROM AFTERNOON/ EVENING SUPERCELLS AND MOVE EWD
TOWARD MS RIVER BY END OF PERIOD. 

--- CENTRAL PLAINS...MID MS VALLEY ---
LAPSE RATES EXPECTED TO BE FAVORABLY STEEP AS BAND OF LARGE-SCALE
ASCENT NEAR AND N OF MID LEVEL CYCLONE PASSES OVER AREA THIS
AFTERNOON. THUNDERSTORMS SHOULD DEVELOP BY MID AFTERNOON AND MOVE
NEWD ACROSS REGION...PERHAPS IN AN ARC INVOF LEADING EDGE OF
STRONGEST LOW LEVEL CONVERGENCE. LOW LEVEL THETAE ADVECTION MAY BE
LIMITED BY LARGE AREA OF CONVECTION FARTHER S/SE...BUT SHOULD BE
SUFFICIENT TO SUPPORT ISOLATED TO WIDELY SCATTERED SEVERE. 
VERTICAL SHEAR PROFILES ARE FORECAST TO BE GENERALLY
UNIDIRECTIONAL....HOWEVER...SUFFICIENT SPEED SHEAR IS EXPECTED TO
ENLARGE HODOGRAPHS AND SUPPORT A FEW ROTATING STORMS. LARGE HAIL
AND A FEW TORNADOES POSSIBLE. SERN PORTION OF ARC MAY EVOLVE INTO
A FEW BOW ECHOES THIS EVENING IF INFLOW IS NOT TOO RESTRICTED BY
CONVECTION FARTHER SE...WITH SOME WIND DAMAGE THREAT.
 
..EDWARDS.. 05/04/99

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