SPC DAY-1 CONVECTIVE OUTLOOK

05 Jun 1999 - 13:04:29 UTC 

ZCZC MKCSWODY1 000
ACUS1 KMKC 051304
MKC AC 051304

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 051300Z - 061200Z

THERE IS A HIGH RISK OF SVR TSTMS OVER PORTIONS CENTRAL/NRN
NEB...S-CENTRAL/SERN SD...NW IA AND SWRN MN...TO THE RIGHT OF A
LINE FROM 20 NNE MCK 30 SW MHN 60 E CDR 35 SSE PHP 10 ENE BKX 45 E
BKX 25 ESE OTG 45 SSW 3SE 25 WNW OMA 15 ENE EAR 20 NNE MCK.

THERE IS A MDT RISK OF SVR TSTMS ELSEWHERE OVER SWRN MN...SRN/ERN
SD...CENTRAL/ERN NEB...AND WRN/NRN IA...TO THE RIGHT OF A LINE FROM
50 WNW 3OI 30 WNW FNB 30 NW CNK 45 NNE HLC MCK 40 WSW MHN
45 ENE CDR 20 SSW PHP 25 N PIR 65 SSW FAR 20 NNW AXN 15 NNW STC
MSP 30 W RST 30 S MCW 30 NNW DSM 50 WNW 3OI.

THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE TO THE RIGHT OF A LINE
FROM 20 E DTW 35 ESE AZO 20 ENE RFD 20 SSE DBQ 40 ENE 3OI 10 W FLV
40 NNE JCT 30 WSW JCT 75 NNW DRT 65 SSE MAF 50 NNE AMA 45 N GCK
10 W MCK 55 NNW IML 30 N BFF 60 ENE 4DG 35 E 81V 40 SW BIS
45 ENE INL.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 40 SE DTW 30 NE FWA
25 SW MMO 35 WNW UIN 20 W SZL 40 SSE CNU 20 NNW SEP 65 WSW COT
...CONT... 25 S P07 25 WNW PVW 35 ENE DHT 35 W GCK 25 SE GLD
15 SW IML 25 NNE AKO 40 W AKO 30 N COS 20 NNE ALS 40 NNW 4SL
40 NE GUP 55 WNW GUP 10 NW GCN 35 S TPH 20 NW NFL 70 ESE 4LW
45 WSW BKE 10 ENE PUW 60 N FCA.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 NW PBG 40 WSW SLK
15 E SYR 50 SE BUF ERI.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 40 SE HUM 15 ENE JAN
45 WSW CBM 30 ENE CBM 20 WNW BHM 45 SW ANB 25 NNW AUO 15 NNE LGC
40 N ATL 50 WNW AND AND 35 NNW AGS 35 ESE SAV.

REGIONAL OUTBREAK WITH TORNADIC SUPERCELLS...EVOLVING INTO MCS
PRODUCING WIND DAMAGE...EXPECTED TODAY OVER PARTS OF CENTRAL/NRN
PLAINS. A FEW SIGNIFICANT TORNADOES ALONG WITH EXTREMELY SEVERE
WIND/HAIL EVENTS ARE POSSIBLE.

--- SYNOPSIS ---
STRONG SHORTWAVE TROUGH AND CYCLONE OVER SWRN CONUS IS FORECAST TO
BEGIN TO EJECT NEWD ACROSS GREAT BASIN/CENTRAL ROCKIES. ASSOCIATED
SURFACE CYCLONE SHOULD DEEPEN IN PLACE OVER WRN NEB TODAY...WITH
DRYLINE SSWWD ACROSS W-CENTRAL TX MOVING EWD. OUTFLOW BOUNDARY
FROM EARLIER CONVECTION IS ANALYZED FROM S-CENTRAL MN SWWD ACROSS
NERN NEB AND INTO SURFACE LOW. WARM FRONT FROM W-CENTRAL MN SEWD
TO NW AL IS FORECAST TO MOVE NEWD...CROSSING MUCH OF GREAT LAKES
AREA BY END OF PERIOD.

COMBINED DRYLINE/PACIFIC FRONT FROM SERN NM NNEWD TOWARD KS/CO
BORDER THEN NNWWD INTO SWRN NEB SURFACE CYCLONE IS FORECAST TO
SURGE ENEWD THIS AFTERNOON ACROSS WRN KS AND SWRN/S-CENTRAL
NEB...FROM BOTH MIXING EFFECTS AND DRY ADVECTION.  

... SEVERE THUNDERSTORM FORECAST DISCUSSION ...

--- NRN/CENTRAL PLAINS ---
CLOUD/PRECIP SWATH ASSOCIATED WITH EXTINCT CONVECTION OVER KS AND
SERN NEB WILL TEMPORARILY IMPEDE DESTABILIZATION OVER SERN PORTIONS
MDT/HIGH RISK AREAS. THIS IS EVIDENT IN POCKET OF RELATIVELY LOW
SURFACE THETAE NOW EXTENDING ACROSS PARTS OF WRN/CENTRAL KS AND S-
CENTRAL NEB...PARTLY RESULTING FROM DRYING EFFECTS OF A HEAT BURST
EPISODE.  

HOWEVER...EXPECT STRONG HEATING AND RETURN-FLOW MOISTENING OF NEAR
SURFACE AIR MASS BY AFTERNOON...UNDERNEATH STEEP LOW-MID LEVEL
LAPSE RATES IN 8.5-9 DEG C/KM RANGE. EARLY VIS IMAGERY INDICATES
RAPID CLEARING OVER WRN PARTS OF MDT/HIGH RISK AREAS...WHERE
CONVECTIVE INITIATION IS EXPECTED...SO HEATING SHOULD BE STRONG
TODAY. THIS WILL LEAD TO MLCAPE 3000-4000 J/KG AND SBCAPES
POSSIBLY TOPPING 5000 J/KG...WITH DEW POINTS INCREASING TO UPPER
60S F OVER W-CENTRAL NEB.

VERTICAL SHEAR IS EXPECTED TO BE QUITE FAVORABLE FOR SUPERCELLS AND
POTENTIALLY SIGNIFICANT TORNADOES...WITH SRH 300-500 J/KG...BRN
SHEARS 70-120 J/KG...AND SR FLOW GENERALLY AOA 20 KT THROUGH MOST
OF TROPOSPHERE. EXPECT 21Z-00Z INITIATION OF STORMS NEAR OR ENE OF
SURFACE LOW...INVOF OUTFLOW/DRYLINE INTERSECTION. GREATEST
POTENTIAL FOR STRONG RIGHT MOTION WILL BE NEAR OUTFLOW
BOUNDARY...WHERE LOW LEVEL VORTICITY/CONVERGENCE/SHEAR IS
MAXIMIZED. HOWEVER DEVELOPMENT ALONG DRYLINE BULGE WRN NEB WILL BE
POTENTIALLY TORNADIC ALSO. DAMAGING HAIL IS QUITE LIKELY WITH
SUPERCELLS IN THIS AREA CONSIDERING SIZE/SHAPE OF CAPE PROFILE AND
STRENGTH OF VERTICAL SHEAR.

ACTIVITY SHOULD EVOLVE INTO SEVERE MCS WITH DAMAGING GUSTS AND
ISOLATED TORNADOES THIS EVENING INTO SERN SD/SWRN MN. THIS
ACTIVITY MAY CONNECT WITH SRN/CENTRAL PLAINS SQUALL
LINE...RESULTING IN A LONG ARC OF SEVERE CONVECTION FROM UPPER MS
VALLEY/NERN PLAINS POSSIBLY AS FAR S AS SRN HIGH PLAINS.

--- SRN PLAINS ---
INCREASINGLY DENSE CIRRIFORM CLOUD BELT WILL SLOW DIURNAL HEATING
THROUGH MOST OF THE DAY ACROSS PORTIONS TX SOUTH PLAINS...AND
PANHANDLE AND WRN OK. EXPECT DRYLINE TO MIX AND ADVECT EWD
SOMEWHAT FARTHER THAN PREVIOUS DAY...PERHAPS INTO ERN PANHANDLES 
AND CLOSE TO WRN EDGE OF CIRRUS SHIELD. DEPENDING ON THEIR
RELATIVE LOCATIONS...HIGH CLOUD PLUME MAY WEAKEN VERTICAL/MIXING
CIRCULATION OF DRYLINE AND DELAY CONVECTION.  

CAP SHOULD REMAIN STRONG FOR MUCH OF DAY OVER THIS AREA...BUT
WEAKEN CONSIDERABLY LATE THIS AFTERNOON OR EARLY EVENING...ALLOWING
RAPID CONVECTIVE DEVELOPMENT IN A BELT OF LOW LEVEL CONVERGENCE
INVOF DRYLINE/FRONT. TIMING AND SRN EXTENT STILL QUITE UNCERTAIN.
VARIOUS ETA-INITIALIZED MODELS ARE VERY INCONSISTENT WITH
CONVECTIVE PRECIPITATION PATTERNS. 05/03Z OPERATIONAL ETA SHOWING
NO CONVECTIVE PRECIP OVER KS...OK...AND ERN TX PANHANDLE BEFORE
06/03Z...WHILE NCAR MM5 DEVELOPS BROKEN BAND NEAR DRYLINE/FRONT...
AND KAIN/FRITSCH ETA SHOWS SUDDEN SQUALL LINE ERUPTION FROM NEB TO
SW TX BETWEEN 21Z-00Z. BASED ON MORNING RAOBS...ESPECIALLY
RELATIVELY WEAK CAP AT MAF VERSUS POINTS E AND NE...MORE SWD
CONVECTIVE DEVELOPMENT IS POSSIBLE AND SLGT RISK IS ADJUSTED
ACCORDINGLY. MAIN THREATS WILL BE DAMAGING GUSTS AND LARGE HAIL. 
VERY DEEP/LARGE CAPE IN OBSERVED AND MODIFIED MAF RAOB...WITH LI
VALUES POTENTIALLY TO NEAR -17 IN 250-300 MB LAYER...SUGGEST
EXCEPTIONALLY INTENSE UPDRAFTS IN HAIL GENERATION ZONES AND THREAT
OF ISOLATED VERY LARGE HAIL.

LARGE COMPONENT OF FLOW WILL BE PARALLEL TO ORIENTATION OF LOW
LEVEL CONVERGENCE ZONE...SO THAT RAPID ACCRETION OF ANVILS AND
LINING OF CONVECTION IS LIKELY ONCE DEVELOPMENT DOES OCCUR. BASED
ON MODIFIED RAOBS AND SOUNDINGS FROM 03Z ETA...PRIND CAP WILL BREAK
IN 00Z-03Z TIME FRAME WITH RAPID DEVELOPMENT OF LINEAR MCS.   
 
..EDWARDS.. 06/05/99

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