SWODY2
SPC AC 040603
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1203 AM CST TUE NOV 04 2008
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS WED/WED NIGHT ACROSS THE
EASTERN PLAINS INTO THE MID/LWR MO VALLEY AND OZARK PLATEAU....
...SYNOPSIS...
LATEST MODEL RUNS AND NCEP SREF/MREF CONTINUE TO INDICATE POTENTIAL
FOR AN OUTBREAK OF SEVERE STORMS ACROSS THE EASTERN PLAINS INTO
PARTS OF THE MID/LOWER MISSOURI VALLEY AND THE OZARK PLATEAU DURING
THIS FORECAST PERIOD. A DEEP SURFACE CYCLONE IS PROGGED TO ALREADY
BE ESTABLISHED ACROSS PARTS OF CENTRAL/EASTERN SOUTH DAKOTA BY 12Z
WEDNESDAY...EAST OF AN AMPLIFIED UPPER TROUGH SLOWLY PROGRESSING
ACROSS THE INTERMOUNTAIN WEST AND ROCKIES. AND...GUIDANCE INDICATES
THAT THE AXIS OF THIS TROUGH WILL SHIFT IN A NEUTRAL TO NEGATIVELY
TILTED FASHION EAST OF THE ROCKIES INTO THE PLAINS BY WEDNESDAY
NIGHT...AS A STRONG EMBEDDED POLAR JET CORE NOSES THROUGH ITS
BASE...ACROSS THE SOUTH CENTRAL PLAINS. AS THIS OCCURS...A
SIGNIFICANT COLD FRONT IS EXPECTED TO SURGE THROUGH MUCH OF THE
PLAINS BY 12Z THURSDAY.
THE LINGERING UNCERTAINTY...AND PRIMARY POTENTIAL LIMITING
FACTOR...REMAINS THE QUALITY OF THE LOW-LEVEL MOISTURE RETURN OFF
THE GULF OF MEXICO PRIOR TO THE FRONTAL PASSAGE. BOUNDARY LAYER
MODIFICATION REMAINS INHIBITED BY THE CONTINUING PRESENCE OF A
SOUTHERN BRANCH TROUGH OVER THE EASTERN GULF INTO WESTERN
ATLANTIC...AND A FAIRLY SIGNIFICANT EMBEDDED LOW/MID-LEVEL CYCLONE
WHICH IS EXPECTED TO PERSIST NEAR SOUTHERN MID ATLANTIC COASTAL
AREAS THROUGH THIS PERIOD. HOWEVER...A NARROW TONGUE OF MOISTURE
RETURN IS NOW EVIDENT IN SATELLITE TOTAL PRECIPITABLE WATER
DATA...ACROSS THE RIO GRANDE VALLEY AND SOUTHERN HIGH PLAINS. THIS
MAY ADVECT NORTHWARD INTO AREAS NEAR/NORTHEAST OF THE SURFACE
CYCLONE BY WEDNESDAY...WHILE A PERHAPS MORE SUBSTANTIVE TONGUE OF
MOISTENING...NOW DEVELOPING EAST OF THE LOWER TEXAS/MEXICAN GULF
COAST...ADVECTS ACROSS THE WESTERN GULF COAST TOWARD THE CENTRAL
PLAINS DURING THE DAY WEDNESDAY.
...PLAINS INTO MO VALLEY/OZARK PLATEAU/ARKLATEX...
STRONG/SEVERE CONVECTIVE DEVELOPMENT MAY BE ONGOING AT THE OUTSET OF
THE PERIOD IN THE WARM SECTOR OF THE SURFACE CYCLONE...AND ALONG AN
ASSOCIATED WARM FRONT...ACROSS PARTS OF THE EASTERN DAKOTAS INTO
NORTHERN MINNESOTA...AS AN INITIAL JET STREAK SHIFTS NORTHWARD TO
THE EAST OF THE UPPER TROUGH AXIS. ACTIVITY MAY PERSIST THROUGH THE
DAY...WITH PERHAPS ADDITIONAL STORM DEVELOPMENT ALONG/AHEAD OF THE
SURFACE COLD...SOUTHWARD THROUGH PARTS OF NEBRASKA BY MID DAY.
BUT...THE MOST SIGNIFICANT DESTABILIZATION...AND PRIMARY SEVERE
POTENTIAL...STILL SEEMS LIKELY TO AWAIT THE ARRIVAL OF THE BETTER
LOW-LEVEL MOISTURE RETURN ACROSS THE CENTRAL PLAINS LATE IN THE
AFTERNOON. MODELS CONTINUE TO SUGGEST THAT A NARROW CORRIDOR OF
SURFACE HEATING ALONG A SHARPENING DRY LINE WILL CONTRIBUTE TO MIXED
LAYER CAPE OF 500-1000 J/KG...AS SURFACE DEW POINTS RISE TO AROUND
60F ACROSS PARTS OF CENTRAL/EASTERN OKLAHOMA AND KANSAS...PERHAPS
NORTHWARD INTO THE MID MISSOURI VALLEY. AND...A WINDOW OF
OPPORTUNITY APPEARS TO EXIST FOR THE DEVELOPMENT OF DISCRETE
SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL/LOCALIZED
DOWNBURSTS...POSSIBLY A COUPLE OF TORNADOES.
MID-LEVEL INHIBITION IS EXPECTED TO PRECLUDE MORE WIDESPREAD STORM
DEVELOPMENT...UNTIL THE PRIMARY MID-LEVEL IMPULSE ASSOCIATED WITH AN
80-90 KT 500 MB JET STREAK PIVOTS TOWARD THE CENTRAL PLAINS EARLY
WEDNESDAY EVENING...AND THE SURGING COLD FRONT OVERTAKES THE DRY
LINE. THE EVOLUTION OF A SEVERE SQUALL LINE IS EXPECTED...WHICH
SHOULD MAINTAIN OR INCREASE THE RISK FOR DAMAGING WINDS AND HAIL
THROUGH THE EVENING...PERHAPS INTO THE OVERNIGHT HOURS...EASTWARD
INTO PARTS OF THE LOWER MISSOURI VALLEY/OZARK PLATEAU AND ARKLATEX.
..KERR.. 11/04/2008
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