[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 182012
SWODY1
SPC AC 182010

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0310 PM CDT SUN JUN 18 2006

VALID 182000Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS LOWER OH TO LOWER TN
VALLEYS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN NEB INTO SWRN IA/FAR
NWRN MO...

...MID MS/LOWER OH VALLEYS...
WATER VAPOR IMAGERY INDICATED A SHORT WAVE TROUGH OVER IL/SERN MO
WITH THIS FEATURE PROGGED MOVE EWD THROUGH THE OH VALLEY THIS
FORECAST PERIOD.  AT THE SURFACE...A WEAK TROUGH EXTENDED SWD FROM
SERN WI THROUGH CENTRAL IL TO SERN MO AND CENTRAL/SWRN AR.  AIR MASS
HAD BECOME MODERATELY UNSTABLE /MUCAPE 1500-2000 J/KG/ IMMEDIATELY
DOWNSTREAM OF MID LEVEL IMPULSE FROM CENTRAL IL INTO SERN MO.  30 KT
OF DEEP LAYER SHEAR SUGGESTS STORMS WILL LIKELY REMAIN MULTICELLULAR
WITH THE POTENTIAL FOR DAMAGING WINDS AND HAIL.  SUFFICIENT LOW
LEVEL DIRECTIONAL SHEAR FROM IL INTO WRN KY INDICATES POTENTIAL FOR
LOW LEVEL STORM ROTATION AND ATTENDANT ISOLATED TORNADO THREAT. 
THUNDERSTORMS WILL SPREAD EWD IN ADVANCE OF SHORT WAVE TROUGH WITH
SEVERE THREAT DIMINISHING THIS EVENING AS THE AIR MASS STABILIZES. 

MEANWHILE...ONGOING CONVECTIVE COMPLEX EXTENDING FROM SWRN IND INTO
NWRN TN WILL PROGRESS ENEWD INTO NRN TN/CENTRAL KY TO SWRN OH AIDED
BY ESTABLISHED COLD POOL AND ASCENT AHEAD OF MID MS VALLEY IMPULSE. 
WEAK INSTABILITY WILL CONTINUE TO MINIMIZE SEVERE THREAT. 
HOWEVER...40 KT WLY WINDS AT 1-2 KM AGL PER FORT CAMPBELL WSR-88D
VAD SUGGESTS POTENTIAL FOR LOCALLY DAMAGING WIND GUSTS.

...LOWER MS/TN VALLEYS...
SRN EXTENT OF MS VALLEY TROUGH WILL CONTINUE TO WEAKEN THIS FORECAST
PERIOD AS IT MOVES SLOWLY EWD ACROSS THE LOWER MS VALLEY.  STRONG
SURFACE HEATING E OF THIS TROUGH OVER MS WITH SURFACE TEMPERATURES
CLIMBING TO AROUND 90 WITHIN A VERY MOIST AIR MASS WILL CONTRIBUTE
TO FURTHER DESTABILIZATION /MLCAPE 1500-2000 J/KG/...GIVEN MODEST
LAPSE RATES /6.5 C/KM/.  GENERALLY WEAK DEEP LAYER SHEAR IS EXPECTED
TO LIMIT SEVERE POTENTIAL.  HOWEVER... MODERATE INSTABILITY
EXTENDING FROM MS INTO SWRN TN MAY ALLOW FOR A FEW DAMAGING WIND
GUSTS THROUGH THE EARLY EVENING...PRIOR TO THE ONSET OF BOUNDARY
LAYER STABILIZATION THIS EVENING.

...NEB/IA...
EARLY AFTERNOON SURFACE ANALYSIS INDICATED A TROUGH/COOL FRONT
EXTENDING FROM THE UPPER MS VALLEY WSWWD THROUGH CENTRAL NEB TO A
MESOLOW NEAR LBF.  SURFACE HEATING S OF THIS TROUGH WITHIN AXIS OF
SURFACE DEWPOINTS IN THE MID-UPPER 50S WILL CONTINUE TO DESTABILIZE
AIR MASS WITH MLCAPE VALUES UP TO 1500 J/KG...WITH RECENT OBJECTIVE
ANALYSES SUGGESTING INHIBITION IS BECOMING WEAKER.  40-50 KT WNWLY
MID LEVEL JET ACCOMPANYING MID MO VALLEY IMPULSE AND AHEAD OF UPPER
TROUGH DEVELOPING SEWD INTO UPPER MS VALLEY IS RESULTING IN STRONG
DEEP LAYER SHEAR SUPPORTING ORGANIZED STORMS.  18Z RUC SUGGESTS
THUNDERSTORM INITIATION WILL BE POSSIBLE BY AROUND 21Z IN VICINITY
OF MESOLOW WHERE LOW LEVEL CONVERGENCE IS MAXIMIZED.  FOR ADDITIONAL
SHORT TERM MESOSCALE INFORMATION...PLEASE REFER TO SPC MESOSCALE
DISCUSSION 1233.

INITIAL STORMS WILL DEVELOP EWD ALONG THE SURFACE FRONT WITH THE
POTENTIAL FOR UPSCALE GROWTH INTO AN MCS THIS EVENING/TONIGHT ACROSS
ERN NEB/SWRN IA INTO NRN MO PER INCREASING WAA ALONG NOSE OF
STRENGTHENING SSWLY LLJ.  HAIL SHOULD BECOME THE PRIMARY THREAT 
TONIGHT AS THE BOUNDARY LAYER DECOUPLES WITH THE LOSS OF DAYTIME
HEATING.

...SERN WI/FAR NERN IL...
WATER VAPOR IMAGERY INDICATED A SHORT WAVE TROUGH CENTERED OVER SERN
WI/FAR NERN IL WHICH IS LIKELY AIDING ONGOING LINE OF STORMS ALONG
NRN EXTENT OF SURFACE TROUGH INTO SERN WI.  MUCAPE 1000-2000 J/KG
COMBINED WITH 20-30 KT OF DEEP LAYER SHEAR SHOULD SUPPORT ADDITIONAL
ORGANIZED LOW-TOPPED SUPERCELLS.  LOW-LEVEL DIRECTIONAL SHEAR WILL
BE SUFFICIENT FOR STORM ROTATION WITH POTENTIAL FOR AN ISOLATED
TORNADO THREAT...IN ADDITION TO HAIL AND STRONG WIND GUSTS.  GIVEN
SMALL AREAL COVERAGE AND SHORT DURATION OF THREAT WILL NOT INTRODUCE
A SLIGHT RISK.

..PETERS.. 06/18/2006