SPC AC 090600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT SAT APR 09 2011
VALID 101200Z - 111200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF IA...WI..SE MN
AND NW IL...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER TO
MID-MS VALLEY...GREAT LAKES...OZARKS AND SRN PLAINS...
...TORNADO OUTBREAK POSSIBLE SUNDAY AFTERNOON AND EVENING ACROSS THE
UPPER MS VALLEY...
...UPPER MS VALLEY...
AN IMPRESSIVE UPPER-LEVEL TROUGH WILL MOVE INTO THE GREAT PLAINS
SUNDAY AS A POWERFUL 90 TO 110 KT MID-LEVEL JET EJECTS NEWD ACROSS
THE CNTRL STATES. AT THE SFC...A STRONG LOW WILL MOVE NEWD INTO IA
SUNDAY AFTERNOON WITH SFC DEWPOINTS REACHING THE LOWER TO MID 60S F
SOUTH OF A WARM FRONT ACROSS MUCH OF THE UPPER MIDWEST. THE EXIT
REGION OF THE JET WILL OVERSPREAD THE UPPER MS VALLEY SUNDAY
AFTERNOON CREATING STRONG DEEP LAYER SHEAR PROFILES VERY FAVORABLE
FOR SEVERE STORMS. THIS COMBINED WITH STRONG INSTABILITY WILL RESULT
IN A SIGNIFICANT POSSIBILITY FOR SUPERCELLS AND TORNADOES ACROSS THE
MODERATE RISK AREA. AN UPGRADE TO HIGH RISK APPEARS LIKELY ACROSS A
PORTION OF THE UPPER MS VALLEY IN LATER OUTLOOKS.
THE CURRENT THINKING IS THAT CELLS WILL FIRST DEVELOP IN NRN IA AND
SE MN AND MOVE INTO NRN WI DURING THE AFTERNOON AHEAD OF THE TRACK
OF A SFC LOW AND ALONG A WARM FRONT. FORECAST SOUNDINGS AT 21Z NEAR
THE WARM FRONT SHOW MLCAPE VALUES AROUND 2000 J/KG...0-6 KM SHEAR
VALUES NEAR 60 KT AND 0-3 STORM RELATIVE HELICITIES OF 250 TO 350
M2/S2. LOW-LEVEL SHEAR SHOULD INCREASE WITH TIME AS A LOW-LEVEL JET
STRENGTHENS AND APPROACHES FROM THE SOUTH. THIS ENVIRONMENT SHOULD
SUPPORT THE DEVELOPMENT OF TORNADIC SUPERCELLS WITH A POTENTIAL FOR
LONG-TRACK TORNADOES WITH CELLS THAT TRACK ENEWD ALONG THE WARM
FRONT. ADDITIONAL SEVERE STORM DEVELOPMENT SHOULD OCCUR SWD ACROSS
THE WARM SECTOR FROM ERN IA NEWD INTO SRN AND CNTRL WI BY EARLY
EVENING. THIS ACTIVITY SHOULD ALSO RAPIDLY BECOME SUPERCELLULAR WITH
TORNADOES AND LARGE HAIL LIKELY WITH THE MORE DOMINANT CELLS. A
THREAT FOR STRONG TORNADOES SHOULD CONTINUE THROUGH MUCH OF THE
EVENING AS A CLUSTER OF SUPERCELLS MOVES ENEWD ACROSS WI. SEVERE
STORMS SHOULD ALSO DEVELOP SWD INTO NRN AND WRN IL WHERE THE
STRONGER CELLS SHOULD HAVE A TORNADO...WIND DAMAGE AND LARGE THREAT
DURING THE EVENING.
...OZARKS/SRN PLAINS...
AN IMPRESSIVE UPPER-LEVEL TROUGH WILL MOVE INTO THE GREAT PLAINS
SUNDAY AS A WELL-DEVELOPED 90 TO 110 KT MID-LEVEL JET EJECTS NEWD
ACROSS THE SRN PLAINS AND OZARKS. THE JET WILL CREATE STRONG DEEP
LAYER SHEAR PROFILES ACROSS MUCH OF THE REGION AS A COLD FRONT
ADVANCES SEWD. THUNDERSTORM DEVELOPMENT SHOULD OCCUR LATE SUNDAY
AFTERNOON FROM NCNTRL MO SWWD ACROSS NW AR INTO ERN OK AND ECNTRL TX
ALONG AN AXIS OF MODERATE INSTABILITY. THE SHEAR ENVIRONMENT SHOULD
SUPPORT SUPERCELL DEVELOPMENT BUT THE FAVORED MODE COULD BE
LINEAR...FORCED BY CONVERGENCE ALONG THE COLD FRONT. STORMS THAT
REMAIN DISCRETE COULD BECOME SUPERCELLS WITH A THREAT FOR ISOLATED
LARGE HAIL. WIND DAMAGE MAY BE THE FAVORED THREAT WITH LINE-SEGMENTS
THAT PERSIST THROUGH THE EVENING WITH THE THREAT GREATEST FROM NW AR
NEWD INTO WCNTRL IL WHERE A 30 PERCENT PROBABILITY IS LOCATED. IF A
SQUALL-LINE DEVELOPS ON THE SERN SIDE OF THE MID-LEVEL JET THEN AN
ENHANCED WIND DAMAGE THREAT COULD EXIST ACROSS ERN AND SRN MO.
...ERN GREAT LAKES AND UPPER OH VALLEY...
AN UPPER-LEVEL RIDGE IS FORECAST TO BE LOCATED ACROSS THE SRN
APPALACHIAN MTNS EXTENDING NWD INTO THE UPPER OH VALLEY SUNDAY. AN
AXIS OF MODERATE INSTABILITY IS FORECAST FROM LOWER MI SEWD ACROSS
OH INTO WV. THUNDERSTORM DEVELOPMENT MAY OCCUR BENEATH THE
UPPER-LEVEL RIDGE AS SFC TEMPS WARM DURING THE DAY. HOWEVER...A LACK
OF LARGE-SCALE ASCENT SHOULD KEEP ANY CONVECTION ISOLATED. STRONG
DEEP LAYER SHEAR AND INCREASING LOW-LEVEL FLOW MAY RESULT IN A
MARGINAL WIND DAMAGE THREAT DURING THE AFTERNOON WHEN LOW-LEVEL
LAPSE RATES SHOULD BE STEEP.
..BROYLES.. 04/09/2011
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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