SWODY2
SPC AC 061645
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1145 AM CDT SUN SEP 06 2009
VALID 071200Z - 081200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PRIMARY FEATURE OF INTEREST DURING THE DAY TWO PERIOD WILL BE
MID/UPPER-LEVEL TROUGH WHICH WILL PROGRESS EWD THROUGH WRN CANADA
AND THE NRN INTERMOUNTAIN REGION INTO THE PRAIRIE PROVINCES AND NRN
HIGH PLAINS. AT THE SURFACE...COLD FRONT ASSOCIATED WITH THIS
SYSTEM WILL SHIFT SLOWLY EWD THROUGH THE WRN/CNTRL DAKOTAS WHILE A
LEE TROUGH IS MAINTAINED OVER THE CNTRL HIGH PLAINS.
...DAKOTAS INTO NEB/WY...
06/12Z REGIONAL SOUNDINGS INDICATED THE PRESENCE OF MODEST BOUNDARY
LAYER MOISTURE OVER THE NRN PLAINS INTO MID MO VALLEY WITH DEWPOINTS
IN THE 50S TO LOWER 60S AND LOWEST 100-MB MEAN MIXING RATIOS OF
10-11 G/KG. BASED ON 12Z MODEL GUIDANCE...A SIMILAR LOW-LEVEL
MOISTURE PROFILE IS FORECAST AHEAD OF COLD FRONT AND LEE TROUGH
MONDAY...WHICH WHEN COUPLED WITH EWD ADVECTION OF EML...WILL
CONTRIBUTE TO A MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF
1000-2000 J/KG.
CAP ASSOCIATED WITH EML WILL LIKELY DELAY MAJORITY OF TSTM
DEVELOPMENT UNTIL AFTERNOON WHEN DAYTIME HEATING AND DEEP ASCENT IN
ADVANCE OF UPPER TROUGH AID IN FOCUSING INITIATION ALONG SURFACE
BOUNDARIES. AS MENTIONED IN PREVIOUS DAY TWO DISCUSSION...STRONGER
SWLY WIND FIELD ASSOCIATED WITH LARGE-SCALE TROUGH WILL LAG SURFACE
WARM SECTOR TO THE W...EFFECTIVELY LIMITING THE POTENTIAL FOR MORE
INTENSE...LONGER-LIVED UPDRAFTS. NONETHELESS...THE PRESENCE OF THE
STEEP LAPSE RATES AND MODERATE CONVECTIVE INSTABILITY WILL BE
SUPPORTIVE OF ISOLATED SEVERE STORMS CAPABLE OF STRONG WIND GUSTS
AND SOME HAIL.
...ERN NC...
WARM CORE CYCLONE CURRENTLY OFF THE SC COAST IS FORECAST TO DEVELOP
SLOWLY NWD OVER THE NEXT 48 HOURS...RESULTING IN AN INCREASE IN
LOW-LEVEL GRADIENT FLOW ACROSS THE AREA. THIS PROCESS WILL COINCIDE
WITH A MOISTENING BOUNDARY LAYER...SUGGESTING SOME THREAT FOR A
BRIEF TORNADO WITH ANY MORE INTENSE CONVECTIVE ELEMENTS EMBEDDED IN
LARGER PRECIPITATION SHIELD. CURRENTLY...THIS THREAT APPEARS QUITE
SMALL AND NO SEVERE PROBABILITIES WILL BE INCLUDED.
..MEAD.. 09/06/2009
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