MODERATE RISK OF SEVERE STORMS IN USA

METD WEATHER
AKSHAY DEORAS
EXTREME WEATHER FORECASTER,

CONCERNING- A MODERATE RISK OF SEVERE STORMS IN PARTS OF MO-IL

VIA STORM PREDICTION CENTER, FORECAST DISCUSSION

SPC AC 301631

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT FRI APR 30 2010

VALID 301630Z - 011200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF IL AND MO...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MS
VALLEY...WRN GREAT LAKES...OZARKS AND SRN PLAINS...

...MID TO UPPER MS VALLEY/OZARKS...
AN MCS CURRENTLY OVER NCNTRL MO WILL CONTINUE ENEWD INTO NCNTRL IL
THIS AFTERNOON. A BROAD LOW-LEVEL JET SOUTH OF THE MCS ACROSS SCNTRL
MO AND AR WILL RESULT IN STRONG MOISTURE ADVECTION. EXPECT MODERATE
DESTABILIZATION ACROSS MUCH OF MO AND AR BY LATE THIS AFTERNOON AS
SFC DEWPOINTS INCREASE INTO THE MID 60S F. MODEL FORECASTS ARE IN
GOOD AGREEMENT...INITIATING NUMEROUS SFC-BASED THUNDERSTORMS ALONG
THE WRN EDGE OF A WELL-DEVELOPED LOW-LEVEL JET FROM ECNTRL MO SSWWD
INTO THE ARKLATEX. THE SHEAR ENVIRONMENT ALONG THIS CORRIDOR WITH
0-6 KM SHEAR VALUES AROUND 50 KT SHOULD BE FAVORABLE FOR NUMEROUS
SEVERE STORMS INCLUDING SUPERCELLS AND ORGANIZED BOWING
LINE-SEGMENTS. A SIGNIFICANT SEVERE WEATHER EVENT WILL BE POSSIBLE
ACROSS THE MODERATE RISK AREA THIS AFTERNOON THROUGH TONIGHT.

THE CURRENT THINKING IS THAT THE LINE OF STORMS IN NW MO WILL BECOME
INCREASINGLY ORGANIZED MOVING ENEWD ACROSS NRN MO AND SE IA THIS
AFTERNOON INTO WRN IL EARLY THIS EVENING. A LINEAR MCS IS EXPECTED
WITH THE STORMS MOVING INTO INCREASING LOW-LEVEL FLOW WHERE FORECAST
SOUNDINGS SHOW ABOUT 50 KT AT 850 MB LATE THIS AFTERNOON. THIS ALONG
WITH INCREASING LARGE-SCALE ASCENT DUE TO A UPPER-LEVEL SYSTEM TO
THE NORTHWEST AND STRENGTHENING MID-LEVEL FLOW ASSOCIATED WITH THE
RIGHT ENTRANCE REGION OF A 90 TO 100 KT MID-LEVEL JET WILL LIKELY
PROMOTE STRONG LINEAR DEVELOPMENT FROM WRN IL SWD ACROSS ECNTRL MO
EARLY THIS EVENING WHERE THE WIND DAMAGE THREAT SHOULD BECOME
ENHANCED. TORNADOES AND LARGE HAIL WILL ALSO BE POSSIBLE ESPECIALLY
WITH SUPERCELLS EMBEDDED IN THE LINE. A 45 PERCENT WIND DAMAGE
PROBABILITY HAS BEEN ADDED FROM NRN IL SWWD ACROSS MOST OF ECNTRL
MO.

FURTHER SOUTH ACROSS SERN MO AND AR...MODEL FORECASTS ARE IN GOOD
AGREEMENT...DEVELOPING NUMEROUS THUNDERSTORMS ALONG THE INSTABILITY
AXIS. THE ENVIRONMENT SHOULD BE CHARACTERIZED BY MODERATE
INSTABILITY AND STRONG DEEP LAYER SHEAR ESPECIALLY NORTH OF LITTLE
ROCK WHERE INTENSE SUPERCELL DEVELOPMENT IS POSSIBLE BY EARLY THIS
EVENING. IN NRN AR...LARGE-SCALE ASCENT IS FORECAST TO BE WEAKER
THAN AREAS TO THE NORTH WHICH SHOULD HELP THE SUPERCELLS REMAIN
DISCRETE BUT THE STORMS MAY BE MORE ISOLATED AS WELL. IN
ADDITION...FORECAST SOUNDINGS ACROSS CNTRL AND NRN AR SHOW SFC WINDS
BACKED TO THE SOUTH SOUTHEAST WHICH COMBINED WITH LOW LCL HEIGHTS
COULD BE FAVORABLE FOR AN ISOLATED STRONG TORNADO. THE MORE DOMINANT
SUPERCELL STRUCTURES SHOULD BE CAPABLE OF PRODUCING TORNADOES AND
POSSIBLY VERY LARGE HAIL. THE THREAT FOR VERY LARGE HAIL SHOULD
EXIST ACROSS AR SWWD INTO NE TX WHERE MODERATE TO STRONG INSTABILITY
IS FORECAST.