SWODY2
SPC AC 291729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT SUN AUG 29 2010
VALID 301200Z - 311200Z
...THERE IS A SLGT RISK OF SVR TSTMS ERN ND...ERN SD...WRN MN AND
NEB...
...SYNOPSIS...
UPPER TROUGH IN THE WEST WILL DEAMPLIFY AS AN INTENSE SHORTWAVE
TROUGH LIFTS NEGATIVELY TILTED FROM THE GREAT BASIN INTO THE NRN
PLAINS. AHEAD OF THIS SYSTEM...SURFACE LOW PRESSURE IS FORECAST TO
BE LOCATED IN CENTRAL SD DURING THE MORNING...AND THEN SHIFT NEWD
INTO ERN ND BY LATE AFTERNOON AND SRN MANITOBA OVERNIGHT. A SURFACE
TROUGH WILL EXTEND SWD FROM THE LOW ACROSS THE CENTRAL/SRN HIGH
PLAINS.
...ERN SD/ND...WRN MN AND NEB...
ALTHOUGH FORECAST SOUNDINGS INDICATE A STRONG LOW LEVEL CAPPING
INVERSION WILL BE IN PLACE DURING THE MORNING...STRENGTHENING LOW
LEVEL JET AND WARM ADVECTION MAY RESULT IN ISOLATED ELEVATED
THUNDERSTORMS. HOWEVER...MAIN THUNDERSTORM ACTIVITY IS EXPECTED TO
WAIT UNTIL LATE IN THE DAY WHEN LARGE SCALE FORCING AND 60-90 M
HEIGHT FALLS SPREAD INTO THE REGION. THIS SHOULD ELIMINATE THE
CAPPING INVERSION AND STRENGTHEN THE LOW LEVEL CONVERGENCE...
ESPECIALLY NEAR SURFACE LOW/TROUGH. EVEN THOUGH TROPOSPHERIC WINDS
WILL BE MOSTLY SLY/SWLY...ONCE SURFACE BASED STORMS DEVELOP... SPEED
SHEAR AND MODERATE INSTABILITY SHOULD BE SUFFICIENT FOR SUPERCELLS.
HAIL IS LIKELY WITH SOME STORMS DUE TO THE DEGREE OF INSTABILITY AND
RELATIVELY STEEP MID LEVEL LAPSE RATES. HOWEVER... WIND DAMAGE
APPEARS TO THE GREATER THREAT...GIVEN THE STRENGTH OF THE
ENVIRONMENTAL WINDS AND A MID LEVEL THERMAL TROUGH SPREADING INTO
THE REGION. LOW LEVEL SHEAR AROUND 20 KT MIGHT ALSO SUPPORT A
TORNADO OR TWO...THOUGH FORECAST SOUNDINGS SHOW DRY ADIABATIC LAPSE
RATES IN THE LOWER 250 MB...SUGGESTING DOWNDRAFTS SHOULD BE TOO
STRONG FOR MORE THAN BRIEF EVENTS. STORMS SHOULD GRADUALLY WEAKEN
OVERNIGHT AS STRONGER FORCING LIFTS NEWD INTO SRN CANADA.
...WRN KS...
COMBINATION OF MOIST TROPICAL PLUME AND SURFACE TROUGH IS EXPECTED
TO GENERATE AT LEAST WIDELY SCATTERED THUNDERSTORMS DURING THE LATE
AFTERNOON AND EVENING HOURS. ALTHOUGH FORCING ASSOCIATED WITH UPPER
TROUGH AND HEIGHTS FALLS WILL BE LOCATED NORTH OF KS...DEEP LAYER
SHEAR AT 30-35 KT AND MLCAPES NEAR 1000 J/KG WOULD SUPPORT A FEW
STORMS. HOWEVER...ONLY 5% SEVERE PROBABILITIES ARE FORECAST ATTM DUE
TO THE WEAK FORCING AND WARM TEMPERATURES ALOFT/ -6C AT 500 MB.
..IMY.. 08/29/2010
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