SWODY2
SPC AC 110525
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1225 AM CDT MON AUG 11 2008
VALID 121200Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL HIGH PLAINS...
...SYNOPSIS...
LARGE-SCALE TROUGHING WILL BE MAINTAINED OVER THE ERN CONUS DURING
THE DAY TWO PERIOD WITH SOME SUPPRESSION OF WRN U.S. RIDGE OCCURRING
DUE TO THE PRESENCE OF UPPER LOW OVER ALBERTA/SASKATCHEWAN. MORE
SPECIFICALLY...A SHORT WAVE TROUGH WILL MOVE SEWD THROUGH THE OZARK
PLATEAU INTO THE LOWER MS VALLEY...WHILE AN UPSTREAM IMPULSE ALSO
SHIFTS SSEWD FROM THE UPPER MS VALLEY INTO IA. IN THE LOW
LEVELS...SURFACE LOW ATTENDANT TO LEAD SHORT WAVE TROUGH WILL
DEVELOP EWD ALONG BAROCLINIC ZONE FROM THE ARKLATEX ACROSS THE GULF
COAST STATES. ELSEWHERE...WEAK LOW PRESSURE WILL DEVELOP SWD FROM
MN INTO IA ALONG COLD FRONT MOVING EWD THROUGH THE UPPER MS AND
MID/LOWER MO RIVER VALLEYS.
...CNTRL HIGH PLAINS...
DEEPENING LEE CYCLONE OVER ERN CO WILL RESULT IN INCREASING ELY/SELY
LOW-LEVEL FLOW ACROSS THE REGION TUESDAY. BOUNDARY LAYER MOISTURE
WILL BE SOMEWHAT MARGINAL /DEWPOINTS IN THE 40S TO LOWER 50S/...BUT
THE PRESENCE OF RATHER STEEP MIDLEVEL LAPSE RATES WILL CONTRIBUTE TO
AN AXIS OF MODERATE INSTABILITY WITH MLCAPES APPROACHING 1000-1500
J/KG. LATEST MODEL GUIDANCE SUGGESTS THAT A LOW AMPLITUDE
DISTURBANCE MAY MOVE THROUGH WY DURING THE DAY...HOWEVER OROGRAPHIC
FORCING WILL LIKELY BE THE PRIMARY MECHANISM INITIATING ISOLATED TO
SCATTERED...DIURNAL TSTM DEVELOPMENT. FORECAST HODOGRAPHS SHOW
CONSIDERABLE VEERING WINDS WITH HEIGHT WITH SUFFICIENT DEEP-LAYER
VERTICAL SHEAR FOR LONGER-LIVED/ROTATING UPDRAFTS. STORMS MAY
PERSIST INTO TUESDAY NIGHT ACROSS THE HIGH PLAINS OF ERN CO...WRN KS
AND SWRN NEB. LARGE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY
SEVERE THREATS WITH THE MOST INTENSE TSTMS.
...IA INTO ERN KS/WRN MO...
A MOIST BOUNDARY LAYER /DEWPOINTS IN THE 60S/ COMBINED WITH DAYTIME
HEATING WILL CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS BY
AFTERNOON AHEAD OF FRONT WITH MLCAPES INCREASING TO 1000-2000 J/KG.
FRONTAL CONVERGENCE AND INCREASING LARGE-SCALE FORCING IN ADVANCE OF
SHORT WAVE TROUGH MOVING SSEWD FROM THE UPPER MS VALLEY ARE EXPECTED
TO RESULT IN AN INCREASE IN TSTM COVERAGE BY MID/LATE AFTERNOON.
THE STRONGEST STORMS WILL BE CAPABLE OF GUSTY WINDS AND SOME HAIL
THROUGH THE EVENING HOURS. HOWEVER...IT APPEARS THAT MARGINAL
MIDLEVEL LAPSE RATES AND VERTICAL SHEAR MAY TEND TO LIMIT A MORE
ORGANIZED SEVERE THREAT.
...ERN TX INTO THE CNTRL GULF STATES...
A VERY MOIST AIR MASS WILL EXIST ALONG/S OF SURFACE BAROCLINIC ZONE
WITH DEWPOINTS IN THE 70S. WIDESPREAD CLOUDS/PRECIPITATION WILL
LIMIT DAYTIME HEATING AND LAPSE RATES...THOUGH POCKETS OF MODERATE
INSTABILITY ARE POSSIBLE WHERE LOCALLY STRONGER INSOLATION CAN
OCCUR. MODEL GUIDANCE SUGGESTS THAT LOWER TO MID-TROPOSPHERIC WIND
FIELDS WILL STRENGTHEN THROUGH THE PERIOD WITH THE APPROACH OF SHORT
WAVE TROUGH. WHEN COMBINED WITH THE MOIST/UNSTABLE
ENVIRONMENT...SOME POTENTIAL WILL EXIST FOR MARGINAL SUPERCELL
STRUCTURES EMBEDDED IN LARGER PRECIPITATION SHIELD. WHILE A BRIEF
TORNADO AND/OR LOCALLY STRONG WIND GUSTS WILL BE POSSIBLE...A MORE
SUBSTANTIAL SEVERE THREAT WILL LIKELY BE LIMITED BY THE MARGINAL
INSTABILITY.
..MEAD.. 08/11/2008
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