000
ACUS01 KWNS 061941
SWODY1
SPC AC 061939

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0239 PM CDT MON SEP 06 2010

VALID 062000Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN MN/WRN
WI/IA...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LOWER-MIDDLE TX
COAST...

HAVE MADE MINOR CHANGES TO 1630Z OUTLOOK AND THOSE ARE PRIMARILY TO
ADDRESS THE DIMINISHING CONVECTIVE POTENTIAL WITHIN POST-FRONTAL
ENVIRONMENT ACROSS THE NRN-CNTRL PLAINS.  LATEST RADAR AND SATELLITE
IMAGERY SUGGEST CONVECTION IS GRADUALLY INCREASING WITHIN REGION OF
STRONG ASCENT ALONG THE SD/MN BORDER...SWD INTO THE MID MO VALLEY. 
AN EVOLVING SQUALL LINE WITH BOW-TYPE CHARACTERISTICS APPEARS TO
REFLECT THIS INCREASING ASCENT AS IT PROPAGATES TOWARD WCNTRL/SWRN
MN.  SWD EXTENT OF THIS ACTIVITY IS STRUGGLING DUE PRIMARILY TO A
STRONG CAP THAT HAS YET TO ERODE - PER 18Z SOUNDINGS AT OAX AND TOP.
IN THE ABSENCE OF SIGNIFICANT MID LEVEL COOLING FARTHER
SOUTH...INTENSE BOUNDARY LAYER HEATING WILL BE REQUIRED ALONG
TRAILING FRONTAL ZONE INTO KS FOR ROBUST UPDRAFT DEVELOPMENT.  FOR
THIS REASON IT APPEARS THE MORE CONCENTRATED ACTIVITY WILL HOLD
ACROSS THE UPPER MS VALLEY AS INDICATED IN CURRENT OUTLOOK SUITE.

SEVERE THREAT WILL CONTINUE TO INCREASE ALONG THE LOWER AND MIDDLE
TX COAST AS THE CENTER OF HERMINE LIFTS NNWWD TOWARD BRO. 
OUTER-MOST BANDS OF STRONG CONVECTION ARE BEGINNING TO ROTATE INTO
DEEP SOUTH TX AND ISOLATED SUPERCELLS SHOULD BECOME MORE COMMON INTO
THE OVERNIGHT HOURS. HAVE ADJUSTED THE RISK OF ISOLATED TORNADOES
WWD TO INCLUDE MORE OF COASTAL SOUTH TX.

..DARROW.. 09/06/2010

.PREV DISCUSSION... /ISSUED 1127 AM CDT MON SEP 06 2010/

...IA/SRN MN/WRN WI LATE THIS AFTERNOON INTO EARLY TONIGHT...
A STRONG MIDLEVEL SHORTWAVE TROUGH WILL MOVE ENEWD FROM THE CENTRAL
HIGH PLAINS TO THE UPPER MS VALLEY BY TONIGHT.  A REMNANT LEE
CYCLONE IN E CENTRAL NEB WILL DEVELOP NNEWD TO SW AND W CENTRAL MN
BY TONIGHT AS THE CYCLONE OCCLUDES...WHILE A TRAILING COLD FRONT
SWEEPS EWD ACROSS IA/WI AND SEWD ACROSS NW MO/KS/NRN OK BY THE END
OF THE PERIOD.  THE WARM SECTOR IN ADVANCE OF THE CYCLONE IS
INITIALLY CAPPED BY A VERY WARM EML...ABOVE A MARGINALLY MOIST
BOUNDARY LAYER WITH DEWPOINTS IN THE LOWER 60S.  THE MARITIME
TROPICAL AIR MASS STILL RESIDES S OF I-20 IN TX PER SURFACE OBS/GOES
PW IMAGERY AND 12Z SOUNDINGS...AND THE RECENT RUC/NAM FORECASTS OF
68-70 F DEWPOINTS INTO IA THIS EVENING APPEAR TOO AGGRESSIVE. 
THUS...EXPECT AT BEST MID 60S DEWPOINTS WITH AFTERNOON
EVAPOTRANSPIRATION AND SOME NEWD MOISTURE ADVECTION FROM OK.

THE VERY WARM EML WILL REQUIRE STRONG ASCENT TO ELIMINATE CONVECTIVE
INHIBITION BY LATE AFTERNOON IN A NARROW BAND ALONG THE COLD
FRONT...WHERE MLCAPE COULD APPROACH 1500-2000 J/KG.  FORECAST WIND
PROFILES AHEAD OF THE FRONT AND E/SE OF THE SURFACE CYCLONE WILL BE
FAVORABLE FOR SUPERCELLS WITH LARGE CLOCKWISE-TURNING HODOGRAPHS. 
DEEP-LAYER SHEAR VECTOR ORIENTATION WILL ALSO FAVOR SEMI-DISCRETE
STORMS FROM IA NWD INTO SRN MN.  IT APPEARS THAT THE MARGINAL
LOW-LEVEL MOISTURE AND STRONG CAP WILL LIMIT THE SPATIAL WINDOW OF
OPPORTUNITY FOR SUPERCELLS AND MAKE IT DIFFICULT FOR STORMS TO
SURVIVE MORE THAN A FEW COUNTIES E OF THE FRONT.  THUS...WILL
MAINTAIN 5% TORNADO AND 15% HAIL/WIND PROBABILITIES IN AN
ENVIRONMENT THAT COULD OTHERWISE SUPPORT A MORE ROBUST SEVERE STORM
THREAT.

A FEW STORMS MAY DEVELOP SWWD ALONG THE COLD FRONT THIS EVENING FROM
NW MO ACROSS ERN KS INTO N CENTRAL OK.  STORM INITIATION WILL DEPEND
ON STRONG LOW-LEVEL ASCENT ALONG THE FRONT AND RELATIVELY DEEP
MIXING FARTHER SW TOWARD NRN OK...AND STORM COVERAGE IS
QUESTIONABLE.  IF STORMS FORM...A FEW STRONG WIND GUSTS AND
MARGINALLY SEVERE HAIL WILL BE POSSIBLE FOR A FEW HOURS THIS
EVENING.

...MIDDLE TX COAST TONIGHT...
TROPICAL STORM HERMINE IS FORECAST TO APPROACH HURRICANE STRENGTH
JUST PRIOR TO LANDFALL ALONG THE LOWER TX COAST LATE TONIGHT /SEE
LATEST NHC ADVISORIES FOR DETAILS/.  DEEPENING OF THE CYCLONE WILL
RESULT IN A CORRIDOR OF INCREASING LOW-LEVEL FLOW/SHEAR TO THE RIGHT
OF THE CYCLONE CENTER...WHICH WILL OVERSPREAD THE MIDDLE TX COAST
OVERNIGHT.  THE CORRIDOR OF INCREASING LOW-LEVEL SHEAR WILL ALSO
COINCIDE WITH MID-UPPER 70S BOUNDARY LAYER DEWPOINTS AND AT LEAST
WEAK SURFACE-BASED INSTABILITY.  GIVEN THESE ENVIRONMENTAL
FACTORS...WILL INTRODUCE A SLIGHT RISK AND 5% TORNADO PROBABILITIES
FOR OUTER BAND SUPERCELLS DURING THE OVERNIGHT PERIOD.