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ACUS01 KWNS 071943
SWODY1
SPC AC 071941

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0241 PM CDT TUE SEP 07 2010

VALID 072000Z - 081200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN/SERN TX...

SEVERE PROBABILITIES FOR ISOLATED TORNADOES REMAIN OVER TX AT 20Z. 
HERMINE CONTINUES ITS NNWWD MOVEMENT AT ROUGHLY 15KT AND IS CENTERED
OVER KENDALL COUNTY IN CNTRL TX...NW OF SAT AT 1930Z.  LATEST
LIGHTNING DATA SUGGEST THE DEEPEST/STRONGEST CONVECTION EXTENDS IN
BANDS FROM THE NWRN GULF OF MEXICO...NWD INTO ERN TX BEFORE ARCING
INTO THE DFW METROPLEX.  GIVEN THAT MINIMAL HEATING IS EXPECTED
INVOF THE ACTUAL LOW CENTER...WILL CONTINUE THE GREATEST RISK OF
TORNADOES BENEATH THE STRONGER BANDS WITHIN THE ERN PERIPHERY.

CONVECTION IS GRADUALLY INCREASING ACROSS CNTRL IND INTO SWRN OH
WITHIN VEERED FLOW AHEAD OF SFC FRONT.  THIS ACTIVITY IS EVOLVING
WITHIN AN AXIS OF MODEST INSTABILITY AND SUFFICIENT VERTICAL SHEAR
FOR ORGANIZED UPDRAFTS.  WILL MAINTAIN 5% PROBS FOR STORMS CAPABLE
OF PRODUCING ISOLATED SEVERE WIND GUSTS AND PERHAPS SOME HAIL. 
STEEP LOW LEVEL LAPSE RATES DUE TO STRONG SFC HEATING WILL
CONTRIBUTE TO STORM INTENSITY AND WITH LOSS OF DAYTIME HEATING THIS
ACTIVITY SHOULD DECREASE.  OTHERWISE...ONLY MINOR CHANGES TO
PREVIOUS OUTLOOK TO ADJUST FOR DIURNAL TENDENCIES AND FRONTAL
POSITION.

..DARROW.. 09/07/2010

.PREV DISCUSSION... /ISSUED 1111 AM CDT TUE SEP 07 2010/

...CENTRAL AND SE TX THROUGH THIS EVENING...
TROPICAL STORM HERMINE MAINTAINS A WELL-DEFINED CIRCULATION TO THE
SSE OF SAT AND IS MOVING LARGELY NWD AT ABOUT 15 KT.  SHORT TERM
MODEL FORECASTS INSIST ON A MORE NWWD MOTION TOWARD W/NW TX
TONIGHT...WHILE EXTRAPOLATION SUGGESTS SW OK BY THE END OF THE
PERIOD.  SEVERAL OUTER CONVECTIVE BANDS WITH SUBSTANTIAL LIGHTNING
AND SOME EMBEDDED WEAK SUPERCELL STRUCTURES PERSIST IN THE ERN
QUADRANTS OF THE SYSTEM.  AN INFLUX OF MID-UPPER 70S DEWPOINTS AND
WEAK SURFACE HEATING IN CLOUD BREAKS...ALONG WITH A BELT OF ENHANCED
LOW-LEVEL FLOW/SHEAR BETWEEN SAT AND HOU...WILL MAINTAIN A THREAT
FOR SUPERCELLS WITH A COUPLE OF TORNADOES THROUGH THE
AFTERNOON/EVENING.

...UPPER OH VALLEY/LOWER GREAT LAKES THIS AFTERNOON/EVENING...
THE OCCLUDED LOW OVER NRN WI/WRN UPPER MI/LAKE SUPERIOR WILL MOVE
EWD OVER SRN ONTARIO TO SWRN QUEBEC...WHILE AN ASSOCIATED COLD FRONT
PROGRESSES SEWD ACROSS THE OH VALLEY THIS EVENING AND THE LOWER
GREAT LAKES EARLY TONIGHT.  LOW-LEVEL MOISTURE IS INITIALLY LIMITED
IN THE PRE-FRONTAL WARM SECTOR WHERE STRONG SURFACE HEATING IS
UNDERWAY FROM KY NEWD INTO OH...THOUGH SOME INCREASE IS EXPECTED
THIS AFTERNOON AS THE NERN FRINGE OF THE TROPICAL MOISTURE PLUME IS
DRAWN NEWD AHEAD OF THE FRONT.  THE NET RESULT WILL BE A NARROW
CORRIDOR OF WEAK INSTABILITY AND STEEP LOW-LEVEL LAPSE
RATES...COINCIDENT WITH THE SRN PORTION OF THE STRONGER LOW-MIDLEVEL
FLOW.

A BROKEN BAND OF THUNDERSTORMS SHOULD DEVELOP BY MID-LATE AFTERNOON
OVER THE LOWER OH VALLEY AND SPREAD NEWD TOWARD THE LOWER GREAT
LAKES THIS EVENING/EARLY TONIGHT.  FORECAST HODOGRAPHS APPEAR
FAVORABLE FOR ORGANIZED LINE SEGMENTS AND/OR SUPERCELLS...BUT THE
WEAK INSTABILITY STILL APPEARS TO BE A LIMITING FACTOR FOR A MORE
ROBUST DAMAGING WIND THREAT.

...ERN NV/WRN UT THROUGH EARLY TONIGHT...
A MIDLEVEL TROUGH CONTINUES TO DIG SEWD OVER THE PAC NW COAST. 
DOWNSTREAM FROM THIS WAVE...THE NRN PORTIONS OF THE SUBTROPICAL
MOISTURE PLUME WILL SPREAD NWD FROM AZ ACROSS ERN NV AND UT.  SOME
INCREASE IN SWLY MIDLEVEL FLOW AND STEEP LAPSE RATES WITH STRONG
SURFACE HEATING ON THE FRINGES OF THE MOISTURE SURGE COULD SUPPORT A
FEW STORMS WITH GUSTY OUTFLOW WINDS THIS AFTERNOON/EVENING FROM ERN
NV INTO NW UT.  HOWEVER...THE SEVERE STORM THREAT APPEARS TOO
MARGINAL TO INTRODUCE ANY DAMAGING WIND PROBABILITIES AT THIS TIME.