SWODY2
SPC AC 120532
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT TUE AUG 12 2008
VALID 131200Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF GA INTO THE
CAROLINAS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL HIGH PLAINS...
...SYNOPSIS...
LARGE-SCALE CYCLONIC FLOW REGIME /ANCHORED BY VORTEX OVER ERN
CANADA/ WILL EXIST OVER THE CNTRL/ERN CONUS DURING THE DAY TWO
PERIOD. FARTHER UPSTREAM...AN UPPER LOW WILL SLOWLY MOVE SWD
THROUGH SASKATCHEWAN INTO THE NRN HIGH PLAINS IN RESPONSE TO
AMPLIFIED RIDGING ALONG THE W COAST. A SERIES OF SMALLER-SCALE
PERTURBATIONS WILL MOVE THROUGH THIS BROADER PATTERN...THE MOST
NOTABLE OF WHICH BEING A STRONG SHORT WAVE TROUGH WHICH WILL
TRANSLATE NEWD THROUGH THE SERN STATES. IN THE LOW-LEVELS...THE
PRIMARY FEATURE OF INTEREST WILL BE DEEPENING SURFACE LOW WHICH WILL
DEVELOP NEWD FROM ERN AL ACROSS THE CAROLINAS. FARTHER W...A LEE
TROUGH WILL STRENGTHEN OVER THE HIGH PLAINS WHILE A WEAK SURFACE
FRONT MOVES SWD THROUGH THE DAKOTAS INTO NEB.
...GA INTO THE CAROLINAS...
MODEL DIFFERENCES STILL EXIST WITH REGARD TO THE INTENSITY AND
TIMING OF AFOREMENTIONED SHORT WAVE TROUGH AND SURFACE LOW. THE GFS
REMAINS MOST PROGRESSIVE WITH THE SURFACE AND UPPER SYSTEMS WHEN
COMPARED TO THE NAM...SHORT RANGE ENSEMBLE MEAN AND 12Z ECMWF
SOLUTIONS. ANOTHER UNCERTAINTY IS THE DEGREE OF INSTABILITY THAT
WILL DEVELOP ACROSS WARM SECTOR OWING TO WEAK LAPSE RATES AND THE
POTENTIAL FOR WIDESPREAD CLOUDS AND PRECIPITATION. THUS...SEVERE
THREAT IS CONDITIONAL ON A SLOWER...MORE AMPLIFIED SYNOPTIC SYSTEM
AND SUFFICIENT INSTABILITY TO INITIATE AND SUSTAIN SURFACE-BASED
STORMS.
LATEST MODEL GUIDANCE DOES SUGGEST THAT MOIST BOUNDARY LAYER
CONDITIONS /DEWPOINTS IN THE 70S/ IN COMBINATION WITH DIABATIC
HEATING SHOULD RESULT IN POCKETS OF STRONGER INSTABILITY WITH
MLCAPES APPROACHING 1000 J/KG. TSTMS ARE EXPECTED TO INCREASE IN
COVERAGE AND INTENSITY BY AFTERNOON FROM ALONG AND AHEAD OF SURFACE
LOW SWWD ALONG TRAILING FRONT AS FORCING FOR ASCENT ATTENDANT TO
MIGRATORY SHORT WAVE TROUGH ACTS ON DESTABILIZING AIR MASS. THE
GREATEST SEVERE WEATHER THREAT /INCLUDING THE POTENTIAL FOR
SUPERCELLS AND/OR BOWING STRUCTURES/ WILL EXIST ALONG THE SURFACE
LOW TRACK WHERE SEASONABLY STRONG WIND FIELDS WILL RESULT IN A
CORRIDOR OF STRONG LOW AND DEEP-LAYER SHEAR. THE PRIMARY SEVERE
THREATS WILL BE DAMAGING WINDS AND A FEW TORNADOES.
...CNTRL HIGH PLAINS...
DEWPOINTS IN THE 50S TO LOWER 60S AND STEEP MIDLEVEL LAPSE RATES
WILL CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS /MLCAPES OF
1000-2000 J PER KG/ WEDNESDAY AFTERNOON E OF LEE TROUGH AND TO THE S
OF FRONT MOVING INTO NEB. GIVEN THE ABSENCE OF ANY APPRECIABLE
SHORT WAVE TROUGHS APPROACHING THE REGION...THERE IS SOME
UNCERTAINTY REGARDING THE TIMING AND LOCATION OF TSTM INITIATION.
IN GENERAL...LATEST MODEL GUIDANCE IS SUGGESTIVE THAT WRN PORTIONS
OF NEB AND KS WILL BE THE MOST FAVORED AREAS BY MID/LATE AFTERNOON.
VERTICAL SHEAR WILL BE SOMEWHAT MARGINAL /DEEP-LAYER SHEAR OF 30-35
KT/...BUT STILL SUFFICIENT FOR STORM ORGANIZATION GIVEN THE
MODERATELY UNSTABLE AIR MASS. THE MOST INTENSE STORMS WILL BE
CAPABLE OF LARGE HAIL AND DAMAGING WIND GUSTS THROUGH THE AFTERNOON
AND EVENING HOURS.
..MEAD.. 08/12/2008
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