Saturday, September 20, 2008

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 200517
SWODY2
SPC AC 200516

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1216 AM CDT SAT SEP 20 2008

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL HIGH
PLAINS...

...CENTRAL HIGH PLAINS...

MODELS CONTINUE TO SUGGEST A SHORTWAVE TROUGH WILL SHIFT EAST ACROSS
THE GREAT BASIN LATE DAY1 BEFORE EJECTING ENEWD INTO THE HIGH
PLAINS. THIS FEATURE WILL LIKELY WEAKEN SOME AS IT ENCOUNTERS
DOWNSTREAM RIDING THAT WILL BE STUBBORNLY SLOW TO BREAK DOWN DUE TO
SPLIT FLOW REGIME. EVEN SO...SHORTWAVE TROUGH WILL UNDOUBTEDLY
ENHANCE THE CONVECTIVE POTENTIAL ACROSS THE NRN/CNTRL
PLAINS...ESPECIALLY DURING THE AFTERNOON INTO THE LATE
EVENING/OVERNIGHT HOURS. LOW LEVEL WARM ADVECTION WILL INCREASE AS
SLY LLJ RESPONDS AND INCREASES FROM THE TX PANHANDLE...NWD TO THE
CANADIAN BORDER. THOUGH BOUNDARY LAYER MOISTURE SHOULD REMAIN
RATHER MODEST...SFC DEW POINTS PRIMARILY IN THE 50S...SUFFICIENT
INSTABILITY WILL DEVELOP ALONG ERN PLUME OF STEEPER LAPSE RATES FOR
ROBUST THUNDERSTORM DEVELOPMENT. FORECAST SOUNDINGS SUGGEST
SFC-BASED CAPE ON THE ORDER OF 1000 J/KG BY PEAK HEATING ACROSS THE
SLIGHT RISK REGION...THUS INCREASING FLOW ALOFT AND FAVORABLE
VEERING PROFILES WOULD SEEM TO FAVOR SLOW MOVING SUPERCELLS BY LATE
AFTERNOON. HAIL SHOULD BE THE PRIMARY SEVERE RISK WITH THIS
ACTIVITY AND SEVERE THREAT WILL LIKELY WANE WITH LOSS OF DAYTIME
HEATING/INSTABILITY.

...ELSEWHERE...

A FEW THUNDERSTORMS ARE POSSIBLE WITHIN RETREATING WARM ADVECTION
ZONE ACROSS THE ARROWHEAD OF MN INTO THE U.P. OF MI. CONVECTION
SHOULD FOCUS INTO SRN CANADA AS WARM FRONT RETREATS INTO
MANITOBA/ONTARIO.

OTHER THUNDERSTORMS WILL LIKELY DEVELOP AHEAD OF WEAK UPPER TROUGH
ACROSS THE LOWER/MID MS VALLEY FROM MO/IL...SWD TO LA. OTHER
ISOLATED STORMS MAY EVOLVE NEAR THE CAROLINA COAST AND THE FL
PENINSULA...HOWEVER DEEP E-NELY FLOW REGIME WILL MAINTAIN WEAK LAPSE
RATES AND PREVENT SIGNIFICANT DESTABILIZATION.

..DARROW.. 09/20/2008

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