DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 271720
SWODY2
SPC AC 271718

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1218 PM CDT THU SEP 27 2012

VALID 281200Z - 291200Z

...NO SVR TSTM AREAS FORECAST...

...SRN PLAINS AND CNTRL PLAINS...
A SUBTLE SHORTWAVE TROUGH WILL MOVE SLOWLY SEWD OUT OF THE CNTRL
ROCKIES INTO THE SRN AND CNTRL PLAINS ON FRIDAY. AT THE SFC...A
SLOW-MOVING FRONTAL BOUNDARY IS FORECAST TO MOVE SWD FRIDAY BEING
POSITIONED FROM THE TX PANHANDLE EWD ACROSS SCNTRL OK AND INTO WRN
AR BY FRIDAY AFTERNOON. AS SFC TEMPS WARM ALONG AND SOUTH OF THE
BOUNDARY FRIDAY...POCKETS OF MODERATE INSTABILITY MAY DEVELOP AS
CONVECTIVE COVERAGE GRADUALLY INCREASES DURING THE DAY. MODEL
FORECASTS DIFFER ON WHERE THE GREATEST CONVECTIVE COVERAGE WILL BE.
THE NAM FAVORS THE CORRIDOR OF STRONGEST INSTABILITY ALONG AND JUST
TO THE SOUTH OF THE BOUNDARY WITH THE GFS HAVING MOST OF THE
CONVECTION NORTH OF THE BOUNDARY. A COMBINATION OF THESE TWO
SCENARIOS SEEMS MOST REASONABLE. AN ISOLATED SEVERE THREAT MAY
DEVELOP FRIDAY AFTERNOON FROM WEST TX EXTENDING EWD ACROSS THE RED
RIVER VALLEY INTO SE OK WHERE MODERATE DESTABILIZATION IS POSSIBLE
LATE FRIDAY AFTERNOON. FORECAST SOUNDINGS ALONG THIS CORRIDOR AT
00Z/SAT SHOW MLCAPE OF 750 TO 1500 J/KG WITH 15 TO 20 KT OF DEEP
LAYER SHEAR. THIS SHOULD SUPPORT A MARGINAL SEVERE THREAT WHERE SFC
HEATING AND THE RESULTANT INSTABILITY BECOMES THE GREATEST.
CONSIDERING LAPSE RATES ARE FORECAST TO BE THE STEEPEST AT
LOW-LEVELS...WIND DAMAGE MAY BE THE FAVORED THREAT ESPECIALLY IF AN
MCS CAN DEVELOP IN THE RED RIVER VALLEY AS IS SUGGESTED BY THE NAM.
HAIL MAY ALSO OCCUR IN THE SRN HIGH PLAINS WHERE MID-LEVEL LAPSE
RATES ARE A BIT STEEPER AND TEMPS ALOFT ARE A BIT COLDER.

..MID-ATLANTIC/SRN APPALACHIAN MTNS...
A BROAD-SCALE UPPER-LEVEL TROUGH WILL MOVE SEWD ACROSS THE GREAT
LAKES REGION ON FRIDAY AND INTO THE CNTRL APPALACHIAN MTNS. AHEAD OF
THE TROUGH...A SFC LOW IS FORECAST TO MOVE NEWD ACROSS THE
MID-ATLANTIC WITH A TRAILING COLD FRONT EXTENDING SWWD INTO THE SRN
APPALACHIAN MTNS. SFC DEWPOINTS ALONG AND SOUTH OF THE BOUNDARY
SHOULD BE IN THE MID TO UPPER 60S F AND SOME MODELS DEVELOP A
CORRIDOR OF MODERATE INSTABILITY FRIDAY AFTERNOON FROM THE NEW YORK
CITY AREA SWWD ACROSS SE VA INTO THE CAROLINAS. SCATTERED
THUNDERSTORMS SHOULD DEVELOP ALONG AND SOUTH OF THE BOUNDARY AS SFC
TEMPS WARM DURING THE DAY. FORECAST SOUNDINGS FRIDAY AFTERNOON ALONG
THE CORRIDOR OF STRONGEST DESTABILIZATION SHOW UNIDIRECTIONAL WIND
PROFILES AND STEEP LOW-LEVEL LAPSE RATES SUGGESTING A MARGINAL WIND
DAMAGE THREAT COULD DEVELOP. HOWEVER...DEEP LAYER SHEAR IS FORECAST
TO BE AROUND 25 KT OR LESS SUGGESTING THE CONVECTION SHOULD REMAIN
UNORGANIZED.

..BROYLES.. 09/27/2012

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