[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 192007
SWODY1
SPC AC 192005

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0305 PM CDT WED JUL 19 2006

VALID 192000Z - 201200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM NRN/ERN IA INTO NRN/CENTRAL
IL...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
FROM THE UPPER MS VALLEY INTO THE UPPER GREAT LAKES...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS
VALLEY/GULF COAST STATES...

...IA INTO NRN IL/NWRN INDIANA...
ONGOING SEVERE MCS MOVING INTO NWRN IL IS EXPECTED TO CONTINUE
MOVING SEWD INTO VERY WARM/MOIST ENVIRONMENT CHARACTERIZED BY
SURFACE TEMPERATURES NEAR 90 AND DEW POINTS IN THE LOW/MID 70S. 
THIS IS RESULTING IN MLCAPE OF 2500-4000 J/KG...AND WITH CONTINUED
AFTERNOON HEATING FURTHER DESTABILIZATION IS LIKELY.  NWLY MID LEVEL
WINDS OF 25-30 KT ACROSS THIS REGION IS CONTRIBUTING TO DEEP LAYER
SHEAR OF 20-30 KT...WHICH IS SUFFICIENT TO MAINTAIN MESOSCALE
ORGANIZATION OF THE CONVECTIVE SYSTEM. VERY LARGE HAIL AND DAMAGING
WIND GUSTS WILL BE LIKELY AS THE STORMS MOVE SEWD 35 KT ACROSS PARTS
OF NRN/CENTRAL IL THIS AFTERNOON.  THIS SYSTEM MAY CONTINUE SEWD
INTO PARTS OF WEST CENTRAL/SWRN INDIANA THIS EVENING BEFORE SLOWLY
WEAKENING AS IT MOVES INTO A REGION OF LESS FAVORABLE SHEAR.

THE CURRENT MCS MOVING INTO NWRN IL HAS GENERATED A CONVECTIVE
OUTFLOW BOUNDARY EXTENDING DIAGONALLY FROM SERN INTO NWRN IA AND
EXTREME SERN SD...WHERE IT INTERSECTS A NE/SW ORIENTED COLD FRONT
EXTENDING FROM NRN MN INTO CENTRAL NEB.  ALTHOUGH VISIBLE IMAGERY
AND RUC FORECAST SOUNDINGS INDICATE THE LOW LEVEL AIR MASS IS
CURRENTLY CAPPED OVER THIS REGION...PERSISTENT CONVERGENCE AND
DYNAMIC FORCING ALONG THE SRN EDGE OF A SHORT WAVE TROUGH MOVING
TOWARD THE UPPER MS VALLEY ARE EXPECTED TO WEAKEN THE CAP
SUFFICIENTLY FOR NEW CONVECTION TO DEVELOP LATER THIS AFTERNOON AND
EVENING.  VERY UNSTABLE CONDITIONS IMMEDIATELY SOUTH OF THE OUTFLOW
BOUNDARY WITH MLCAPE EXCEEDING 4000 J/KG COUPLED WITH STRONG DEEP
LAYER SHEAR/LOW LEVEL HELICITY INDICATE A FAVORABLE ENVIRONMENT FOR
SUPERCELL THUNDERSTORMS CAPABLE OF PRODUCING VERY LARGE
HAIL...DAMAGING WIND GUSTS...AND A FEW TORNADOES /PRIMARILY ALONG
AND JUST NORTH OF THE OUTFLOW BOUNDARY/.  SEVERE CONVECTION IS
FORECAST TO GROW UPSCALE INTO ANOTHER MCS LATER THIS EVENING AND
TRACK ESEWD ALONG THE OUTFLOW BOUNDARY ACROSS THE MIDDLE MS
VALLEY...WITH A CONTINUED THREAT FOR DAMAGING WIND GUSTS AND LARGE
HAIL THROUGH THE OVERNIGHT HOURS.

...UPPER MS VALLEY INTO THE UPPER GREAT LAKES...
ALTHOUGH THE CIRRUS CANOPY ASSOCIATED WITH THE IA/IL MCS EXTENDS NWD
INTO SRN MN AND WI...LATEST VISIBLE IMAGERY SHOWS THINNING CLOUDS
NEAR THE FRONT OVER EAST CENTRAL MN AND FAR NWRN WI.  THIS MAY
PERMIT ENHANCED HEATING AND AIR MASS DESTABILIZATION TO
OCCUR...INCREASING THE POTENTIAL FOR ADDITIONAL STRONG/SEVERE STORMS
TO DEVELOP ALONG/AHEAD OF THE ADVANCING COLD FRONT.  A 50-60 KT MID
LEVEL JET STREAK MOVING EWD ACROSS THIS AREA IN ASSOCIATION WITH THE
SHORT WAVE TROUGH WILL INCREASE THE DYNAMIC FORCING FOR LARGE SCALE
ASCENT AND CONTRIBUTE TO STRONG DEEP LAYER SHEAR.  ALTHOUGH THE
ENVIRONMENT IS LESS UNSTABLE COMPARED TO REGIONS FARTHER
SOUTH...THERE WILL CONTINUE TO BE A THREAT FOR SEVERE THUNDERSTORMS
SPREADING EWD ACROSS THIS REGION LATER THIS AFTERNOON INTO TONIGHT.

...UPPER TN VALLEY INTO THE GULF COAST REGION...
SCATTERED THUNDERSTORMS HAVE DEVELOPED FROM NRN AL SWD INTO PARTS OF
SWRN GA/SRN AL AND CENTRAL/SRN MS.  THIS ACTIVITY IS WITHIN A 
THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY AMPLE MOISTURE AND STEEP
LAPSE RATES IN THE LOWEST 1-2 KM...WITH DRY AIR AND MODERATELY STEEP
LAPSE RATES ALOFT.  20-25 KT NELY MID LEVEL WINDS WILL SUPPORT
MODEST CONVECTIVE ORGANIZATION AND HELP MAINTAIN A THREAT FOR WET
MICROBURSTS AND POSSIBLE HAIL WITH STRONGER CELLS.

...SRN APPALACHIANS NWD INTO PARTS OF VA...
18Z GSO AND RNK RAOBS EXHIBIT VERY STEEP LOW LEVEL LAPSE RATES AND
LARGE SURFACE TEMPERATURE/DEW POINT SPREADS...WHICH WILL ENHANCE
DOWNDRAFT STRENGTH.  WEAK WINDS ALOFT AND MINIMAL VERTICAL SHEAR
INDICATES LIKELIHOOD OF PULSE STORMS WITH ATTENDANT POTENTIAL FOR
BRIEF MICROBURSTS.  THIS CONVECTION SHOULD WEAKEN AFTER SUNSET.

..WEISS.. 07/19/2006