SWODY2
SPC AC 210600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE SEP 21 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SD/NEB/IA AND
SWRN MN...
...SYNOPSIS...
A LARGE MID-LEVEL TROUGH INITIALLY ALONG THE W COAST IS FORECAST TO
SHIFT EWD ACROSS THE ROCKIES THIS PERIOD...WITH A SMALLER-SCALE LEAD
FEATURE TO MOVE INTO THE HIGH PLAINS DURING THE SECOND HALF OF THE
PERIOD.
AS THE UPPER SYSTEM ADVANCES...SURFACE CYCLOGENESIS IS FORECAST OVER
THE CENTRAL HIGH PLAINS. MEANWHILE...INCREASING SLY WARM SECTOR
FLOW ACROSS THE PLAINS WILL RESULT IN THE NWD RETREAT OF A W-E
BAROCLINIC ZONE -- THE TRAILING PORTION OF AN ERN NOAM COLD FRONT
WHICH SHOULD MOVE OFF THE NEW ENGLAND COAST LATE. THE DEVELOPING
SURFACE LOW AND RETREATING WARM FRONT WILL SERVE AS A FOCUS FOR
WIDESPREAD CONVECTION THIS PERIOD.
...SRN SD/NRN NEB/SWRN MN/NRN IA.
PERSISTENT RIDGING ACROSS THE PLAINS WILL CONTRIBUTE TO A CAPPED
BOUNDARY LAYER...THUS LIMITING CONVECTIVE DEVELOPMENT THROUGH MUCH
OF THE AFTERNOON DESPITE HEATING/DESTABILIZATION OF THE WARM SECTOR
AIRMASS.
AS THE UPPER SYSTEM APPROACHES AND SURFACE CYCLOGENESIS
PERSISTS...ISOLATED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ACROSS
THE HIGH PLAINS REGION. MORE SUBSTANTIAL CONVECTIVE
DEVELOPMENT...HOWEVER...IS FORECAST TO OCCUR NEAR AND N OF THE
RETREATING WARM FRONT...AS WARM ADVECTION/QG FORCING INCREASE.
STORMS SHOULD EXPAND THROUGH THE LATE AFTERNOON AND INTO THE
EVENING...WITH THE OVERALL ZONE OF MOST ACTIVE CONVECTION TO SHIFT
NWD WITH TIME AS THE LOW MOVES NEWD INTO THE PLAINS LATE.
WITH LOW-LEVEL SLYS INCREASING WITH TIME AS STRONGER MID-LEVEL SWLYS
SPREAD EWD INTO THE PLAINS...SHEAR WILL INCREASINGLY SUPPORT
SEVERE/SUPERCELL STORMS. ISOLATED STORMS WHICH SHOULD DEVELOP OVER
THE HIGH PLAINS WILL LIKELY BECOME CAPABLE OF HAIL AND DAMAGING
WINDS...THOUGH GREATEST THREAT -- PRIMARILY IN THE FORM OF LARGE
HAIL -- WILL EXIST WITH MORE WIDESPREAD/ELEVATED CONVECTION NORTH OF
THE WARM FRONT. EXPECT SOME SEVERE THREAT TO PERSIST INTO THE
OVERNIGHT HOURS...WITH STORMS LIKELY ONGOING THROUGH THE END OF THE
PERIOD.
..GOSS.. 09/21/2010
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