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000
ACUS01 KWNS 210101
SWODY1
SPC AC 210059

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT MON MAY 20 2013

VALID 210100Z - 211200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF MO...NW AR...ERN
OK...SRN OK AND NORTH TX...

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

...SRN PLAINS/OZARKS/MID-MS VALLEY...
LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH OVER THE
CNTRL AND SRN PLAINS WITH SOUTHWEST FLOW LOCATED FROM THE TROUGH
AXIS NEWD INTO THE MID-MS VALLEY. AN MCS IS CURRENTLY ONGOING ALONG
THIS CORRIDOR ON THE WRN EDGE OF A 30 TO 40 KT LOW-LEVEL JET. THE
LOW-LEVEL JET WILL CONTINUE TO STRENGTHEN EARLY THIS EVENING HELPING
TO MAINTAIN INTENSE CONVECTION ACROSS THE MODERATE RISK AREA. SFC
DEWPOINTS AHEAD OF THE MCS ARE IN THE UPPER 60S TO NEAR 70 F AND
OBJECTIVE ANALYSIS SHOWS MLCAPE VALUES IN THE 2500 TO 3500 J/KG
RANGE. THIS ALONG WITH 35 TO 45 KT OF DEEP LAYER SHEAR ACROSS THE
MODERATE RISK AREA DUE TO A CNTRL PLAINS MID-LEVEL JET...WILL
CONTINUE TO SUPPORT WIDESPREAD SEVERE THUNDERSTORMS THIS EVENING
WITH A SEVERE THREAT LASTING INTO THE OVERNIGHT PERIOD.

REGIONAL WSR-88D VWPS FROM ST. LOUIS SSWWD TO SPRINGFIELD MO INTO
NCNTRL TX SHOW DIRECTIONAL TURNING IN THE LOWEST 2 KM WITH
SUBSTANTIAL SPEED SHEAR RESULTING IN 0-3 KM STORM RELATIVE
HELICITIES IN THE 300 TO 400 M2/S2 RANGE. THIS ALONG WITH MODERATE
TO STRONG INSTABILITY SUGGESTS THAT THE THREAT FOR TORNADIC
SUPERCELLS WILL EXIST ACROSS AN AREA EXTENDING FROM CNTRL MO SWWD
INTO NORTH TX. AS THE LOW-LEVEL JET CONTINUES TO STRENGTHEN...A
POTENTIAL FOR STRONG TORNADOES WILL EXIST ACROSS THE MODERATE RISK
AREA. CONCERNING THE THREAT FOR LARGE HAIL...THE STEEPEST MID-LEVEL
LAPSE RATES EXIST ACROSS ERN OK AND NCNTRL TX WHERE THE MORE INTENSE
SUPERCELL WILL BE CAPABLE OF PRODUCING HAIL GREATER THAN 2 INCHES IN
DIAMETER. SUPERCELLS SHOULD ALSO BE CAPABLE OF PRODUCING SWATHS OF
WIND DAMAGE. THE WIND DAMAGE THREAT SHOULD BECOME ENHANCED EARLY
THIS EVENING AS THE MCS BECOMES INCREASINGLY LINEAR AND AS THE
LOW-LEVEL JET INTENSIFIES. THE SEVERE THREAT IS EXPECTED TO CONTINUE
INTO PART OF THE OVERNIGHT PERIOD DUE TO AMOUNT OF INSTABILITY THAT
IS CURRENTLY LOCATED AHEAD OF THE MCS.

...UPPER MS VALLEY/WRN GREAT LAKES...
AN UPPER-LEVEL LOW IS CURRENTLY LOCATED ACROSS THE NRN PLAINS
ACCORDING TO WATER VAPOR IMAGERY. AT THE SFC...A COLD FRONT IS
MOVING THROUGH THE NRN AND CNTRL PAINS WITH A CORRIDOR OF LOW-LEVEL
MOISTURE EXTENDING NWD INTO THE UPPER MS VALLEY. SFC DEWPOINTS
ACROSS THE UPPER MS VALLEY ARE IN THE UPPER 50S TO LOWER 60S F WITH
MID 60S F LOCATED IN LOWER MI. THIS IS RESULTING IN MLCAPE VALUES
ESTIMATED IN THE 750 TO 1250 J/KG RANGE ACROSS MUCH OF THE REGION.
IN ADDITION...OBJECTIVE ANALYSIS SHOWS 0-6KM SHEAR VALUES IN THE 40
TO 50 KT RANGE ACROSS THE NRN PART OF THE SLIGHT RISK AREA. AS THE
EXIT REGION OF A 70 TO 80 KT MID-LEVEL JET OVERSPREADS THE REGION
EARLY THIS EVENING...DEEP LAYER SHEAR WILL BE ENHANCED HELPING TO
SUPPORT SEVERE THUNDERSTORM DEVELOPMENT. MODEL FORECASTS SUGGEST
THAT THUNDERSTORM ACTIVITY WILL INCREASE IN COVERAGE THIS
EVENING...WITH STORMS MOVING NEWD ACROSS SRN MN...WI AND NRN IL. THE
ENVIRONMENT SHOULD SUPPORT SCATTERED SEVERE STORMS CAPABLE OF
PRODUCING WIND DAMAGE AND LARGE HAIL. AS LOW-LEVEL SHEAR INCREASES
THIS EVENING...A FEW TORNADOES MAY ALSO OCCUR WITH THE MORE INTENSE
CELLS. THE SEVERE THREAT SHOULD BECOME MORE ISOLATED AFTER MIDNIGHT
DUE TO THE WEAKER INSTABILITY THAT IS IN PLACE COMPARED TO AREAS
FURTHER SOUTH.

..BROYLES.. 05/21/2013