SWODY1
SPC AC 071947
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT SAT MAY 07 2011
VALID 072000Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN IL AND MUCH OF
IND...
...IL/IND...
UNCERTAINTY STILL EXISTS WITH REGARDS TO CONVECTIVE
INITIATION...WITH THE 19Z ILX SOUNDING REFLECTIVE OF WEAK CONVECTIVE
INHIBITION REMAINING. CU FIELD IS BEGINNING TO INCREASE IN FAVORABLE
AREAS OF SURFACE CONFLUENCE...FROM NEAR ST LOUIS NWD TO NWRN
IND...AND A SEPARATE AREA IN ERN IA/W CNTRL IL THAT MAY BE FAVORED
AREAS FOR INITIAL DEVELOPMENT. 19Z WV IMAGERY AND RECENT
DETERMINISTIC MODEL DATA SUGGESTS THE STRONGEST MID-LEVEL JET WINDS
ARE CURRENTLY FROM SWRN MN INTO CNTRL IL...WHICH WILL ENHANCE
VERTICAL MOTION ACROSS CNTRL IL INTO IND. GIVEN CLOCKWISE TURNING OF
HODOGRAPHS AND STEEP MID-LEVEL LAPSE RATES NEAR 7.5 C/KM PER
MESOANALYSIS...ROTATING STORMS CAPABLE OF HAIL AND PERHAPS AN
ISOLATED TORNADO REMAIN POSSIBLE SHOULD STORMS DEVELOP. REFERENCE MD
0698 FOR MORE INFORMATION.
...SERN SD/NERN NEB...
WARM ADVECTION REGIME MAY SUPPORT THE DEVELOPMENT OF A SMALL CLUSTER
OF ELEVATED STORMS OVERNIGHT. HEIGHT RISES/LARGE SCALE SUBSIDENCE
MAY HINDER A MORE WIDESPREAD THREAT...BUT FAVORABLE SHEAR/ELEVATED
INSTABILITY MAY LEAD TO HAIL FORMATION IN STORMS THAT CAN DEVELOP.
..HURLBUT/GUYER.. 05/07/2011
.PREV DISCUSSION... /ISSUED 1120 AM CDT SAT MAY 07 2011/
...IL/IND...
AS ALLUDED TO IN 13Z OTLK DISCUSSION AN UPGRADE TO SLGT RISK APPEARS
LIKE A REASONABLE APPROACH TO THE FCST THIS AFTERNOON AND EVENING
ACROSS ERN IL AND MUCH OF CNTRL IND. THERE IS VERY GOOD CONSENSUS
AMONGST STORM SCALE GUIDANCE THAT AT LEAST ISOLD TSTM DEVELOPMENT
WILL OCCUR NEAR WEAK SFC LOW/WAVE TRACKING EAST ACROSS THESE AREAS
LATER TODAY. SHORT WAVE TROUGH EVIDENT IN SATELLITE IMAGERY AND
MODEL DIAGNOSES ACROSS IA ATTM IS EXPECTED TO ENHANCE LARGE SCALE
ASCENT OVER THE AREA COINCIDENT WITH BOUNDARY LAYER HEATING AND
MODEST DESTABILIZATION /SBCAPE TO 1000 J PER KG/. GIVEN HEATING AND
PERSISTENT LOW LEVEL CONVERGENCE NEAR SFC LOW/WAVE...GENERALLY WEAK
CAPPING SHOULD BE OVERCOME WITH THE POTENTIAL FOR TSTM INITIATION
OCCURRING AROUND 21 UTC.
WNWLY FLOW ALOFT AND 50-60KT JET STREAK TRAVERSING THE
REGION...COUPLED WITH WEAKER LOW LEVEL SWLY FLOW...WILL CONTRIBUTE
TO EFFECTIVE SHEAR VALUES SUPPORTIVE OF SUPERCELLS. LOCALLY BACKED
LOW LEVEL WINDS NEAR SFC LOW/WAVE MAY ENHANCE HODOGRAPH CURVATURE
AND LOW LEVEL SRH. LATEST INDICATIONS SUGGEST THAT ISOLATED TO
WIDELY SCATTERED STORMS MAY INITIATE AND PERSIST FOR A FEW HOURS IN
THIS ENVIRONMENT AND RESULT IN A FEW LARGE HAIL EVENTS AND PERHAPS
EVEN A TORNADO OR TWO.
...NORTHEAST...
A FEW MARGINALLY SEVERE HAILSTORMS APPEAR POSSIBLE FROM NERN PA AND
NRN NJ ACROSS SERN NY AND SRN NEW ENGLAND THROUGH THE AFTERNOON.
HEIGHT FALLS AND STEEPENING DEEP-LAYER LAPSE RATES ASSOCIATED WITH
UPPER TROUGH CROSSING THE NORTHEAST TODAY HAVE ALREADY SUPPORTED THE
DEVELOPMENT OF SHOWERS AND LOW-TOPPED TSTMS ACROSS NRN PA/WRN NY.
MINUS 25C TO -28C COLD POOL AT 500MB AND LOW FREEZING
LEVELS...COUPLED WITH DIURNAL HEATING...WILL CONTRIBUTE TO MLCAPE
VALUES PERHAPS CLIMBING TO 500 J/KG. BACKGROUND ASCENT WITH THE
UPPER TROUGH AND GENERALLY WEAK EFFECTIVE SHEAR SUGGEST POORLY
ORGANIZED/SHORT-LIVED STORMS WITH A LOW PROBABILITY OF HAILSTONES
REACHING 1 INCH IN DIAMETER.
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