SPC DAY-1 CONVECTIVE OUTLOOK

08 Apr 1999 - 12:35:58 UTC 
disclaimer  "for information regarding the availability and timeliness of 
forecasts and products.

ZCZC MKCSWODY1 000
ACUS1 KMKC 081235
MKC AC 081235

CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O.

VALID 081300Z - 091200Z

REF WW NUMBER 131...VALID TIL 1700Z

THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING ACROSS
MUCH OF EASTERN MISSOURI...EXTREME SOUTHEAST IOWA...WEST CENTRAL/
CENTRAL AND SOUTHWEST ILLINOIS...AND PARTS OF NORTHEAST ARKANSAS TO
THE RIGHT OF A LINE FROM TBN COU IRK 35 NNW IRK OTM 30 WSW MLI PIA
DEC 25 ESE CGI JBR 60 WSW ARG TBN.

SURROUNDING THE HIGH RISK AREA...THERE IS A MDT RISK OF SVR TSTMS
ACROSS MUCH OF THE LOWER MISSOURI AND MIDDLE MISSISSIPPI VALLEY TO
THE RIGHT OF A LINE FROM BIE OLU SUX FOD DBQ 25 SW CGX LAF OWB MKL
MEM LIT FSM UMN MKC BIE.

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM MCK
IML MHN ANW FSD FRM MSN BEH TOL CAK HLG 5I3 CSV MSL TUP GLH TXK
DUA ADM PNC HUT RSL MCK.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 NE ERI BFD
15 W BGM 35 E ART 25 NNE BTV 40 NNE BML 10 SW 47B ...CONT...
25 S CTY AUO ELD SEP OKC 35 SW ICT 35 SSW HLC GLD AKO CYS GCC RAP
ATY MSP GRB MBS 35 NE MTC ...CONT... PBI FMY.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM LAS 60 W DRA
45 W BIH 35 ENE SAC LOL BAM DPG PUC CNY PGA 60 S SGU LAS.

SURFACE LOW HAS DEEPENED RAPIDLY PAST SEVERAL HOURS OVER NORTHEAST
COLORADO IN RESPONSE TO CLOSED UPPER LOW AND TRAILING SHORT WAVE
TROUGH MIGRATING ACROSS THE CENTRAL ROCKIES. SURFACE DATA AT 11Z
INDICATED LOWEST PRESSURE AROUND 989 MB AT AKRON CO...WITH PRESSURE
CONTINUING TO FALL. STRONGEST 2 HOUR PRESSURE FALLS ARE SHIFTING
EASTWARD INTO THE MID MISSOURI VALLEY...WHERE DESTABILIZATION HAS
SUPPORTED RAPID CONVECTIVE DEVELOPMENT IN ZONE OF STRONGEST WARM
ADVECTION...JUST NORTH OF SURFACE WARM FRONT WHICH EXTENDS EAST OF
SURFACE LOW INTO THE LOWER OHIO VALLEY. THIS ACTIVITY IS EXPECTED
TO INCREASE THROUGH THE DAYTIME HOURS...SPREADING ACROSS THE MIDDLE
MISSISSIPPI AND LOWER OHIO VALLEYS AS UPPER LOW/TROUGH MIGRATE
EASTWARD ACROSS THE CENTRAL PLAINS.

ALTHOUGH INTENSE MID-LEVEL JET STREAK ACCOMPANYING UPPER SYSTEM
INTO THE CENTRAL HIGH PLAINS IS PROGD BY ALL MODELS TO SLOWLY
WEAKEN THROUGH THE FORECAST PERIOD...WESTERLY 500 MB SPEED MAXIMUM
OF 80 TO 90 KT IS STILL PROGD ACROSS CENTRAL MISSOURI BY THE LATE
AFTERNOON HOURS. THIS WILL CONTRIBUTE TO VERY STRONG VERTICAL
SHEAR PROFILES IN THE VICINITY OF 50+ KT SOUTHERLY LOW-LEVEL
JET...AHEAD OF DRY LINE WHICH IS PROGD TO SURGE EAST NORTHEASTWARD
ACROSS MISSOURI...TO THE VICINITY OF THE MISSISSIPPI RIVER BY
09/00Z.

DRY LINE IS EXPECTED TO BECOME FOCUS FOR MOST INTENSE CONVECTIVE
DEVELOPMENT THROUGH THE PERIOD...WITH MOST CONCENTRATED ACTIVITY
NEAR DRY LINE/WARM FRONT INTERSECTION ACROSS SOUTHEAST IOWA/
NORTHEAST MISSOURI/WEST CENTRAL ILLINOIS...WHERE UPPER FORCING IS
STRONGEST BY LATE AFTERNOON...BEFORE SHIFTING ACROSS ILLINOIS/
INDIANA AND OHIO OVERNIGHT. SCATTERED INTENSE CELLS APPEAR LIKELY
SOUTHWESTWARD ALONG DRY LINE...POSSIBLY AS FAR AS THE ARKLATEX
REGION...FORCED PRIMARILY BY LOW-LEVEL WARM ADVECTION AND
CONVERGENCE NEAR/JUST AHEAD OF SURFACE BOUNDARY.

VERY MOIST AIR MASS IS RETURNING NORTHWARD THROUGH THE MISSISSIPPI
VALLEY AHEAD OF DRY LINE...WITH LOWER/MID 60S SURFACE DEW POINTS
EXPECTED THROUGH MUCH OF THE MIDDLE MISSISSIPPI VALLEY BY LATE
AFTERNOON. THIS WILL CONTRIBUTE TO STRONG CONVECTIVE INSTABILITY
AND CAPE AOA 1500 J/KG AS DRY AIR MID-LEVEL AIR MASS WITH STEEP
LAPSE RATES ADVECTS INTO REGION FROM THE SOUTHERN/CENTRAL PLAINS. 
GIVEN STRENGTH OF VERTICAL SHEAR PROFILES AND FORCING FOR UPWARD
VERTICAL MOTION...INSTABILITY IS EXPECTED TO SUPPORT OUTBREAK OF
SEVERE THUNDERSTORMS ACROSS THE MIDDLE MISSISSIPPI AND LOWER OHIO
VALLEYS. ACTIVITY WILL INCLUDE A FEW SUPERCELLS...WITH ISOLATED
...POSSIBLY STRONG TORNADOES DURING THE LATE AFTERNOON AND EARLY
EVENING HOURS...BEFORE DAMAGING WIND BECOMES PRIMARY THREAT ACROSS
THE LOWER OHIO VALLEY OVERNIGHT.

ISOLATED TORNADIC SUPERCELLS WILL ALSO BE POSSIBLE CLOSER TO
SURFACE LOW AND COLD MID-LEVEL CIRCULATION CENTER...PRIMARILY FROM
MID AFTERNOON THROUGH EARLY EVENING ACROSS PARTS OF EASTERN
NEBRASKA/SOUTHERN IOWA AND NORTHERN MISSOURI
 
..KERR.. 04/08/99

NNNN


 
Experimental Tornado Probability Graphic 
 Return to 
SPC Forecasts page 
 Storm Prediction Center Home 
Page