[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 170605
SWODY2
SPC AC 170604

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0104 AM CDT THU AUG 17 2006

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE DAKOTAS AND
NERN NEB...

...SYNOPSIS...
UPPER TROUGH CURRENTLY MOVING INTO THE INTERIOR NORTHWEST WILL BRING
MODEST MID LEVEL HEIGHT FALLS FROM THE NRN PLAINS TO UPPER MS VALLEY
THROUGH EARLY SATURDAY. THIS DISTURBANCE WILL CONTINUE TO DAMPEN THE
NRN PERIPHERY OF THE LARGE UPPER HIGH BLANKETING MUCH OF THE CNTRL
AND SRN U.S...AND WILL INDUCE FRONTAL WAVE DEVELOPMENT ACROSS SD
FRIDAY AFTERNOON. COLD FRONT ACCOMPANYING UPPER TROUGH AND
ASSOCIATED SURFACE WAVE WILL SPREAD SOUTH ACROSS THE CNTRL PLAINS
THROUGH FRIDAY NIGHT AS UPPER TROUGH AND SURFACE LOW TRACK GENERALLY
EAST TOWARD THE UPPER MS VALLEY.

NAM-WRF AND GFS MODELS DIFFER SLIGHTLY ON THE TIMING OF THE NRN
STREAM FEATURES WITH THE GFS INDICATING A FASTER EWD/SEWD MOVEMENT
TO THE UPPER TROUGH AND COLD FRONT THROUGH EARLY SATURDAY. THIS
OUTLOOK IS FURTHER COMPLICATED BY A SERIES OF MORE SUBTLE
SUBTROPICAL SRN STREAM DISTURBANCES IN WEAKER FLOW AROUND THE NRN
EDGE OF THE DEEP-LAYER ANTICYCLONE. A LEADING FEATURE IN THIS WAVE
TRAIN WAS ALREADY AIDING MESOSCALE CONVECTIVE COMPLEX OVER THE MO
VALLEY ATTM. ADDITIONAL IMPULSES ARE FORECAST TO EVOLVE AND EMANATE
FROM HIGH PLAINS CONVECTION OVER THE NEXT DAY OR SO. THESE WEAK
DISTURBANCES WILL SPREAD EAST AND ENHANCE ASCENT ATOP A
QUASI-STATIONARY WARM FRONT FROM MO/IA...ACROSS THE MIDWEST...TO THE
OH VALLEY THROUGH EARLY SATURDAY.

...DAKOTAS/NEB...
STRONGER FORCING ASSOCIATED WITH UPPER TROUGH AND COLD FRONT WILL
SPREAD ESEWD OVER THE NRN PLAINS DURING THE DAY AND ENHANCE LIFT
ACROSS INCREASINGLY UNSTABLE AIR MASS. MODELS APPEAR TO BE
OVERFORECASTING LOW LEVEL MOISTURE ACROSS THE AREA BUT MLCAPE VALUES
TO 2000 J/KG APPEAR POSSIBLE OVER NEB/SD GIVEN MID TO UPPER 60S
DEWPOINTS AND TEMPERATURES IN THE 80S TO 90S. SUFFICIENT SHEAR AND
INSTABILITY ARE FORECAST ACROSS SERN ND AND SD FOR SUPERCELLS WITH
HAIL. TORNADO POTENTIAL MAY INCREASE SHOULD THIS CONVECTION REMAIN
DISCRETE AND PERSIST NEAR SURFACE WAVE.

ACROSS NEB...SHEAR WILL INITIALLY BE WEAKER BUT POTENTIAL
INSTABILITY IS FORECAST TO BE GREATER. HEATING AND LARGE SCALE LIFT
WILL ACT TO OVERCOME THE CAP ACROSS THIS AREA AND SHOULD RESULT IN
SCATTERED TSTM DEVELOPMENT THROUGH EVENING. ROBUST MULTICELL
CONVECTION SHOULD POSE SOME THREAT OF LARGE HAIL AND LOCAL DOWNBURST
WINDS BEFORE COLD FRONT MOVES ACROSS THE REGION OVERNIGHT.

...MO/IA EAST TO OH VALLEY...
AN MCS OR TWO MAY BE ONGOING AT THE START OF THE PERIOD WITHIN
PLAINS WARM CONVEYOR BELT FROM MO VALLEY EAST ACROSS THE MS VALLEY.
CONVECTION MAY REGENERATE OR CONTINUE TO SPREAD EAST ACROSS THE
MIDWEST THROUGH THE DAY SUSTAINED BY MCVS/SHORT WAVE TROUGHS AND
PERSISTENT WARM AIR ADVECTION ON THE EDGE OF THE STRONGER CAP.
POCKETS OF GREATER MID LEVEL FLOW ASSOCIATED WITH MCVS/SUBTLE SHORT
WAVES...COUPLED WITH AREAS OF STRONGER DESTABILIZATION...COULD
SUPPORT CLUSTERS OF SEVERE STORMS WITH WIND AND HAIL. UNCERTAINTIES
WITH RESPECT TO TIMING AND AMPLITUDE OF MID LEVEL IMPULSES...CAP
STRENGTH...LOCATION OF MCS OUTFLOW...AND STRENGTH OF SHEAR...ALL
PLAY INTO KEEPING SEVERE PROBABILITIES LOW AT THIS TIME.

..CARBIN.. 08/17/2006