Saturday, January 7, 2012

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 071626
SWODY1
SPC AC 071624

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1024 AM CST SAT JAN 07 2012

VALID 071630Z - 081200Z

...NO SVR TSTM AREAS FORECAST...

...LOWER MS/TN VALLEY REGION THROUGH TONIGHT...
A NRN STREAM SHORTWAVE TROUGH WILL CONTINUE EWD FROM THE GREAT LAKES
TO NEW ENGLAND...AS AN ASSOCIATED COLD FRONT MOVES SLOWLY SEWD
ACROSS SRN AR...NW MS...WRN/MIDDLE TN...AND KY. THE FRONT EXTENDS
WWD TO A WEAK LOW IN NE TX THAT IS BEING MAINTAINED BY THE APPROACH
OF A WEAK EMBEDDED SHORTWAVE TROUGH MOVING EWD OVER SE OK/NE TX.
PHASING OF THE SE OK TROUGH WITH THE RIGHT ENTRANCE REGION OF THE
GREAT LAKES UPPER JET HAS SUPPORTED A BAND OF ASCENT AND ELEVATED
THUNDERSTORMS OVER NRN MS THIS MORNING. REGIONAL 12Z SOUNDINGS
SHOWED MUCAPE OF 250-750 J/KG BASED IN THE 900-850 MB LAYER...AND
THE RISK FOR A FEW THUNDERSTORMS WILL PERSIST THROUGH MIDDAY-EARLY
AFTERNOON...UNTIL THE BAND OF ASCENT BEGINS TO PROGRESS E OF THE
UNSTABLE WARM SECTOR.

MEANWHILE...DAYTIME HEATING/MIXING WILL ESTABLISH THE SURFACE WARM
SECTOR FROM EXTREME SE TX ACROSS LA/MS. THE MAGNITUDE OF WARM
SECTOR INSTABILITY WILL BE LIMITED BY MIDLEVEL LAPSE RATES OF ONLY
6-6.5 C/KM...BUT CONVECTIVE INHIBITION WILL BE WEAK ONCE SURFACE
TEMPERATURES REACH 65-70 F. THE COMBINATION OF A MINIMAL CAP AND
SOMEWHAT NEBULOUS FORCING FOR ASCENT WILL SUPPORT ISOLATED-WIDELY
SCATTERED AFTERNOON SHOWERS/TSTMS. DEEP-LAYER VERTICAL SHEAR WILL
BE MARGINALLY FAVORABLE FOR PERSISTENT STORMS...BUT THE POOR LAPSE
RATES AND RELATIVELY WEAK LOW-LEVEL SHEAR SUGGEST THAT SEVERE STORMS
ARE UNLIKELY.

...UT/WRN CO THIS AFTERNOON...
A PRONOUNCED SHORTWAVE TROUGH IS DIGGING SSEWD FROM UT/NV TOWARD AZ.
ASCENT DOWNSTREAM FROM THIS WAVE AND STEEP LAPSE RATES WILL PROMOTE
THE DEVELOPMENT OF SHALLOW CONVECTION. HOWEVER...LIMITED
MOISTURE/BUOYANCY SUGGEST THAT LITTLE IF ANY LIGHTNING WILL OCCUR
WITH THIS CONVECTION ACROSS UT/WRN CO.

..THOMPSON/JIRAK.. 01/07/2012

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