SWODY1
SPC AC 171618
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1018 AM CST SAT JAN 17 2009
VALID 171630Z - 181200Z
...NO TSTM AREAS FORECAST...
...SYNOPSIS...
THE LARGE SCALE MID-UPPER TROUGH OVER THE ERN CONUS WILL BE
REINFORCED BY A SHORTWAVE TROUGH DIGGING SSEWD OVER THE UPPER MS
VALLEY...WHILE AN UPSTREAM RIDGE WILL REMAIN OVER THE PAC NW.
THE UPPER MS VALLEY SHORTWAVE WILL BE ACCOMPANIED BY A SURFACE
CYCLONE THAT WILL DEVELOP EWD FROM WI TO LOWER MI BY TONIGHT...WHILE
A TRAILING SURFACE TROUGH PROGRESSES SEWD INTO TX AND THE LOWER MS
VALLEY BY THE END OF THE PERIOD. A MODIFYING CP AIR MASS /BOUNDARY
LAYER DEWPOINTS OF 56-60 F/ WILL RETURN NWD/NEWD TO THE NW GULF
COAST THROUGH TONIGHT IN ADVANCE OF THE SURFACE TROUGH.
HOWEVER...THIS MOISTENING WILL OCCUR BENEATH RATHER POOR MID LEVEL
LAPSE RATES. THE OPERATIONAL NAM IS THE MOST AGGRESSIVE OF THE
MODELS IN GENERATING SUFFICIENT INSTABILITY FOR DEEP
CONVECTION/LIGHTNING PRODUCTION LATE TONIGHT NEAR THE UPPER TX
COAST...WHILE MODIFIED OBSERVED PROFILES AND FORECAST SOUNDINGS FROM
THE NAM KF/GFS APPEAR QUITE MARGINAL FOR THUNDERSTORMS. GIVEN THE
UNCERTAINTIES AND MARGINAL NATURE OF ANY POTENTIAL THUNDERSTORM
THREAT...WILL NOT INTRODUCE AN OUTLOOK AREA IN THIS UPDATE.
..THOMPSON.. 01/17/2009
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