[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 191628
SWODY1
SPC AC 191626

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1126 AM CDT WED JUL 19 2006

VALID 191630Z - 201200Z

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON/EVENING ACROSS
NRN IA...SRN WI...AND NRN IL...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
ACROSS MOST OF THE UPPER MS VALLEY AND PARTS OF MI...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON ACROSS THE LOWER
MS VALLEY...

...IA/MN/WI/IL THIS AFTERNOON/EVENING...
A MID LEVEL SHORTWAVE TROUGH OVER THE NRN HIGH PLAINS WILL AMPLIFY
SOME AND MOVE ESEWD TO THE UPPER MS VALLEY BY TONIGHT...WHILE AN
ASSOCIATED SURFACE COLD FRONT MOVES SEWD FROM THE ERN DAKOTAS TO NW
WI/CENTRAL IA/SRN NEB. THE SURFACE PATTERN IS COMPLICATED BY AN
ONGOING MCS ACROSS SE MN/SW WI/NE IA.  THIS CONVECTION DEVELOPED IN
ASSOCIATION WITH LOW-LEVEL WAA AND A MID LEVEL SPEED MAX OVER NERN
SD THIS MORNING.  GIVEN THE WELL-DEVELOPED COLD POOL/BOW
ECHO...MERGING CLUSTERS...AND A DESTABILIZING BOUNDARY LAYER IN
ADVANCE OF THE STORMS...THE THREAT FOR DAMAGING WINDS APPEARS TO BE
INCREASING ACROSS SRN WI AND NRN IL THIS AFTERNOON.

OUTFLOW WITH THIS CONVECTION WILL ALSO MODULATE THE NWD PROGRESSION
OF THE VERY UNSTABLE WARM SECTOR ACROSS IA/MN/WI.  THE 12Z NAM
REFLECTS THIS SCENARIO BY MAINTAINING THE ONGOING STORMS THROUGH THE
DAY.  HOWEVER...THIS MODEL APPEARS TO BE SEVERAL HOURS TOO SLOW WITH
THE PROGRESSION OF THE MORNING STORMS. STRONG/EXTREME INSTABILITY
IS EXPECTED ALONG THE TRAILING OUTFLOW BOUNDARY ACROSS IA...ALONG
WITH SUFFICIENT VERTICAL SHEAR FOR SUPERCELLS. ADDITIONAL
CONVECTION MAY FORM ALONG THE OUTFLOW ACROSS NW/N CENTRAL IA BY
MID-LATE AFTERNOON...AND THEN MOVE ESEWD ACROSS THE REMAINDER OF IA
AND INTO NRN IL TONIGHT.  THE INITIAL STORMS MAY BE SUPERCELLS
CAPABLE OF PRODUCING VERY LARGE HAIL AND A FEW TORNADOES WHERE
LOW-LEVEL MOISTURE/SHEAR ARE ENHANCED ALONG THE BOUNDARY. THIS
CONVECTION MAY GROW UPSCALE THIS EVENING INTO ANOTHER FORWARD
PROPAGATING MCS WITH DAMAGING WINDS.

...LOWER MS VALLEY THIS AFTERNOON...
WATER VAPOR IMAGERY SHOWS A WEAK MID LEVEL WAVE MOVING SWWD OVER NE
MS.  THE COMBINATION OF THIS WEAK MID LEVEL DISTURBANCE AND A
DIFFUSE SFC TROUGH SHOULD HELP FOCUS THE DEVELOPMENT OF SEVERAL
MULTICELL THUNDERSTORM CLUSTERS THIS AFTERNOON.  MODIFYING THE 12Z
JAN SOUNDING FOR AFTERNOON SURFACE TEMPERATURES IN THE LOW-MID
90S...MLCAPE WILL APPROACH 3000 J/KG AND LAPSE RATES FROM THE
SURFACE TO NEAR 500 MB WILL BE NEAR 8 C/KM.  THE 12Z SHV SOUNDING
SHOWS A SIMILAR ENVIRONMENT...WITH SOMEWHAT STRONGER /30 KT/ NELY
MID LEVEL FLOW AND MODEST DEEP LAYER SHEAR.  A FEW DAMAGING
DOWNBURSTS SHOULD BE THE MAIN THREAT...THOUGH ISOLATED LARGE HAIL
WILL ALSO BE POSSIBLE WITH THE MOST INTENSE STORMS.

..THOMPSON/GUYER.. 07/19/2006