SWODY1
SPC AC 182000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SUN JUL 18 2010
VALID 182000Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE GREAT LAKES VICINITY
AND OH VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL PLAINS...
...GREAT LAKES VICINITY/MIDWEST/OH VALLEY...
LITTLE CHANGE IN PRIOR FORECAST REASONING /SEE DISCUSSION
BELOW/...WITH SOME ADJUSTMENTS MADE TO LOWER SEVERE RISK AREAS IN
THE WAKE OF THE EARLY DAY SEVERE MCS ACROSS PORTIONS OF MO/IL INTO
KY. A MULTICELLULAR MODE WITH WIND DAMAGE AS THE PRIMARY HAZARD IS
STILL EXPECTED TO BE DOMINANT ACROSS THE REGION.
...CENTRAL HIGH PLAINS...
ATTRIBUTABLE TO AN INCREASING MOIST EASTERLY UPSLOPE REGIME...TSTMS
SHOULD INCREASE LATE THIS AFTERNOON/EARLY EVENING ACROSS THE
NORTH-CENTRAL HIGH PLAINS. FOR ADDITIONAL INFORMATION...SEE
MESOSCALE DISCUSSION 1351. TONIGHT...STRONG/SEVERE TSTM POTENTIAL IS
EXPECTED TO TRANSLATE EAST-SOUTHEASTWARD LATE THIS
EVENING/OVERNIGHT...MAINLY ACROSS PORTIONS OF SOUTHERN SD/NORTHERN
NEB TO WESTERN IA IN CONCERT WITH AN INCREASING WARM
ADVECTION/MOISTURE TRANSPORT REGIME. SEVERE HAIL/DAMAGING WINDS WILL
BE POSSIBLE.
..GUYER.. 07/18/2010
.PREV DISCUSSION... /ISSUED 1119 AM CDT SUN JUL 18 2010/
...MO/AR INTO LOWER OH VALLEY...
A LONG-LIVED MCS WHICH STARTED YESTERDAY OVER THE EASTERN DAKOTAS IS
NOW TRACKING INTO PARTS OF SOUTHERN MO/IL. THESE STORMS HAVE
WEAKENED SLIGHTLY THROUGH THE MID-LATE MORNING HOURS...BUT SHOULD
RE-INTENSIFY THIS AFTERNOON AS THEY MOVE INTO A VERY MOIST AND
MODERATELY UNSTABLE AIR MASS ACROSS PARTS OF AR/KY/TN. THE ACTIVITY
IS MOVING SOUTHEASTWARD INTO A PROGRESSIVELY LESS SHEARED
ENVIRONMENT AS IT MOVES SOUTH OF THE STRONGER WESTERLIES ALOFT.
HOWEVER...MESOSCALE ORGANIZATION OF MCS SUGGESTS THAT STORMS MAY
REMAIN CAPABLE OF LOCALLY DAMAGING WINDS THROUGH THE AFTERNOON.
...KY/IN/OH/MI...
A COMBINATION OF WEAK OUTFLOW BOUNDARIES FROM MORNING CONVECTION AND
A COLD FRONT APPROACHING FROM THE NORTHWEST WILL HELP TO INITIATE
SCATTERED THUNDERSTORMS THIS AFTERNOON FROM EASTERN IL INTO LOWER
MI. CONSIDERABLE CLOUD DEBRIS FROM OVERNIGHT STORMS HAS RETARDED
SURFACE HEATING...BUT BREAKS IN THE CLOUDS SHOULD LEAD TO RAPID
DESTABILIZATION THIS AFTERNOON WITH MLCAPE VALUES OF 2000-3000 J/KG.
FORECAST SOUNDINGS IN THIS ZONE SHOW SUFFICIENT EFFECTIVE SHEAR FOR
ORGANIZED MULTICELL OR ISOLATED SUPERCELL STORMS CAPABLE OF LARGE
HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES. GREATEST TORNADO
THREAT WOULD BE OVER PARTS OF LOWER MI IN VICINITY OF WEAK SURFACE
LOW. STORMS MAY PERSIST THROUGH THE EVENING AND SPREAD ACROSS MUCH
OF OH BEFORE WEAKENING.
...WY/SD/NEB/KS...
A WEAK SURFACE BOUNDARY EXTENDS FROM CENTRAL KS INTO NORTHEAST CO.
EASTERLY LOW LEVEL WINDS TO THE NORTH OF THE BOUNDARY ARE HELPING TO
TRANSPORT RICH MOISTURE WESTWARD WITH DEWPOINTS CLIMBING THROUGH THE
60S ACROSS SOUTHWEST NEB/NORTHWEST KS. UPSLOPE FLOW WILL HELP TO
INITIATE SCATTERED THUNDERSTORMS OVER SOUTHEAST WY AND NORTHEAST CO
LATER THIS AFTERNOON. THESE STORMS WILL SPREAD EAST-SOUTHEASTWARD
DURING THE EVENING. STRONGER CELLS IN THIS REGION WILL POSE A RISK
OF DAMAGING WINDS AND HAIL.
FARTHER NORTH...INCREASING LOW LEVEL WINDS WILL ENHANCE WARM
ADVECTION AND LIFT NORTH OF THE BOUNDARY AFTER DARK. THIS IS
EXPECTED TO LEAD TO AT LEAST ISOLATED THUNDERSTORM DEVELOPMENT FROM
SOUTHERN SD INTO NORTHERN/CENTRAL NEB...MAINLY AFTER MIDNIGHT. THESE
STORMS WILL POSE A RISK OF HAIL.
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