SWODY2
SPC AC 050600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT SUN SEP 05 2010
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE UPPER
MIDWEST/UPPER MS VALLEY...
...SYNOPSIS...
00Z NAM/GFS GUIDANCE REMAIN IN GENERAL AGREEMENT THAT A BASAL
SHORTWAVE PORTION OF THE CURRENT BRITISH COLUMBIA/PACIFIC NORTHWEST
UPPER TROUGH WILL ULTIMATELY PIVOT NORTHEASTWARD/TAKE ON MORE OF A
NEGATIVE TILT ON LABOR DAY FROM THE NORTHERN HIGH PLAINS TO THE
UPPER MS RIVER VALLEY. ASSOCIATED NORTHEASTWARD ADVANCING SURFACE
LOW/EASTWARD ADVANCING COLD FRONT WILL FOCUS THE
PRIMARY DEEP CONVECTIVE POTENTIAL ACROSS THE UPPER MIDWEST/UPPER MS
RIVER VALLEY MONDAY/MONDAY NIGHT.
...UPPER MIDWEST/UPPER MS RIVER VALLEY...
SOME TIMING DIFFERENCES ASIDE...LATEST NUMERICAL GUIDANCE STILL
SUGGESTS THAT THE BRUNT OF THE AFOREMENTIONED UPPER TROUGH WILL BE
CROSSING THE MIDDLE MO RIVER VALLEY VICINITY MONDAY AFTERNOON...WITH
APPRECIABLE LARGE SCALE FORCING FOR ASCENT/HEIGHT FALLS FOCUSED
DOWNSTREAM ACROSS PORTIONS OF IA/MN TO THE ADJACENT UPPER MS RIVER
VALLEY. BASED ON THE LATEST OBSERVATIONAL DATA...RECENT COLD FRONTAL
PASSAGE /NOW ALONG THE GULF COAST/...AND THE RESIDUAL INFLUENCE OF
EASTERN STATES SURFACE HIGH PRESSURE/ASSOCIATED TRAJECTORIES...WILL
LIKELY ONLY BE CONDUCIVE FOR A NARROW WARM MOIST SECTOR WITH MAINLY
LOWER 60S F SURFACE DEWPOINTS ALONG/AHEAD OF THE ADVANCING SURFACE
LOW/COLD FRONT.
TSTMS /SOME POTENTIALLY STRONG TO SEVERE/ ARE INITIALLY EXPECTED
FROM THE DAKOTAS INTO WESTERN MN...BUT WITH A STRONG EML
OVERSPREADING MUCH OF THE MODESTLY MOIST WARM SECTOR...CONSEQUENTIAL
SURFACE BASED TSTM DEVELOPMENT WILL LIKELY BE DELAYED UNTIL LATE
AFTERNOON/EARLY EVENING ACROSS THE MAJORITY OF THE SURFACE FRONTAL
ZONE ACROSS SOUTHERN MN AND IA TO THE ADJACENT LOWER MO VALLEY.
HERE...SUFFICIENT PRE-FRONTAL HEATING COUPLED WITH THE EXPECTED
MODEST MOISTURE CONTENT COULD SUPPORT MLCAPES TO HIGH AS 1000-2000
J/KG -- LIKELY MAXIMIZED ACROSS IA. THE DEGREE OF LARGE SCALE
FORCING ACCOMPANIED BY STEEP LAPSE RATES ALOFT AND INCREASINGLY
ROBUST WIND PROFILES /60-90 KT AT 500 MB WITH 45-60 KT AT 850 MB/
WILL LIKELY SUPPORT AT LEAST A SEVERAL HOUR TEMPORAL WINDOW FOR
EARLY MODAL SUPERCELLS AND OTHERWISE FAST MOVING LINEAR
SEGMENTS/BOWS CAPABLE OF DAMAGING WINDS/SOME HAIL AND PERHAPS A
TORNADO OR TWO. THE SEVERE THREAT WILL LIKELY CONTINUE
EAST-NORTHEASTWARD INTO WI DURING THE EVENING HOURS. WHILE THE COLD
FRONT/EXPECTED ONGOING TSTM CLUSTERS WILL TEND TO OUTRUN THE MAIN
RESERVOIR OF INSTABILITY IN ADDITION TO A TENDENCY FOR A DECOUPLING
BOUNDARY LAYER...BOUTS OF WIND DAMAGE MAY CONTINUE THROUGH THE
EVENING GIVEN THE MAGNITUDE/DEEPENING PHASE OF THE PARENT SYSTEM.
...SOUTH TX...
DISTURBANCE/SURFACE TROUGH EXISTS ACROSS THE WESTERN GULF OF MEXICO
PER LATEST SATELLITE IMAGERY...REFERENCE THE LATEST NHC
OUTLOOKS/DISCUSSIONS. LATEST AVAILABLE GUIDANCE IS HIGHLY VARIABLE
REGARDING THIS SYSTEM...WITH THE 00Z NAM MOST AGGRESSIVE IN TERMS OF
ORGANIZATION/ENHANCED WIND FIELDS POTENTIALLY DEVELOPING/SPREAD
ACROSS THE FAR SOUTH TX COAST MONDAY NIGHT/EARLY TUESDAY. GIVEN A
HIGH DEGREE OF UNCERTAINTY...SEVERE PROBABILITIES ARE NOT WARRANTED
AT THIS TIME.
..GUYER.. 09/05/2010
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