SWODY2
SPC AC 050557
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1157 PM CST TUE NOV 04 2008
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU ACROSS PARTS OF THE WRN
GULF COAST THRU THE LWR MISSISSIPPI VALLEY....
...SYNOPSIS...
CONSIDERABLE VARIABILITY PERSISTS WITHIN THE MODEL DATA CONCERNING
THE DETAILS OF THE EVOLVING CYCLONE OVER THE UPPER MIDWEST DURING
THIS PERIOD. FURTHER DEEPENING OF THIS FEATURE MAY OCCUR...AS THE
PRIMARY SHORT WAVE IMPULSE PIVOTS AROUND ITS EASTERN/NORTHERN
PERIPHERY. BUT...IT STILL APPEARS THAT THE EASTWARD PROGRESSION OF
THE LARGER-SCALE AMPLIFIED POLAR TROUGH ENCOMPASSING MUCH OF THE
PLAINS AND MISSISSIPPI VALLEY WILL SLOW...WITH ANOTHER EMBEDDED
SHORT WAVE TROUGH DIGGING SOUTHEASTWARD NEAR AND TO THE LEE OF THE
CENTRAL/SOUTHERN ROCKIES. AT THE SAME TIME...THE LOW/MID LEVEL
CYCLONE WITHIN THE SOUTHERN BRANCH OF SPLIT DOWNSTREAM WESTERLIES IS
STILL PROGGED TO BE SLOW TO SHIFT AWAY FROM THE MID ATLANTIC COAST.
...UPPER MISSISSIPPI VALLEY INTO GREAT LAKES...
DUE TO THE INFLUENCE OF THE DOWNSTREAM SOUTHERN BRANCH LOW...WARM
SECTOR GULF MOISTURE RETURN THROUGH THE CENTRAL U.S. IS NOT EXPECTED
TO BECOME PARTICULARLY BROAD OR STRONG. AND...MOISTURE THAT DOES
RETURN IS EXPECTED TO BECOME CUT OFF FROM THE OCCLUDING SURFACE LOW
OVER MINNESOTA EARLY THURSDAY...AS A WEAKENING FRONTAL/PRE-FRONTAL
CONVECTIVE BAND ADVANCES EAST OF THE MID/UPPER MISSISSIPPI VALLEY.
WHILE THE VIGOR OF THE CONVECTION MAY BE LIMITED BY WEAK
INSTABILITY...IT MAY STILL BE STRONG ENOUGH TO ENHANCE DOWNWARD
TRANSPORT OF HIGHER MOMENTUM AIR NEAR A SOUTHERLY JET CORE /40-50
KTS AT 850 MB...70-90 KT AT 500 MB JET/ LIFTING AROUND THE LOW
TOWARD THE GREAT LAKES REGION...SUPPORTING THE RISK FOR AT LEAST
SPORADIC DAMAGING WIND GUSTS.
...MID MS/LWR OH VALLEYS THRU LWR MS VLY/WRN GULF COAST...
BEFORE LOW-LEVEL FLOW WEAKENS AND VEERS TO A MORE WESTERLY COMPONENT
LATE THURSDAY AFTERNOON OR THURSDAY NIGHT...LOWER LEVELS MAY
CONTINUE TO MOISTEN WITHIN A SHRINKING WARM SECTOR WEDGE ACROSS THE
REGION. GUIDANCE HINTS AT A POSSIBLE LINGERING PRE-FRONTAL DRY LINE
STRUCTURE FROM PARTS OF EASTERN TEXAS THROUGH CENTRAL/EASTERN
ARKANSAS...PERHAPS AS FAR NORTHEAST AS THE MISSOURI BOOTHEEL
REGION...WHERE CONVECTIVE INSTABILITY MAY BECOME SOMEWHAT ENHANCED
IN THE CONTINUING PRESENCE OF SUFFICIENT DEEP LAYER SHEAR FOR
SUPERCELLS. DISCRETE STORM DEVELOPMENT SEEMS POSSIBLE...BUT FRONTAL
FORCING COUPLED WITH THE TENDENCY TOWARD INCREASINGLY UNIDIRECTIONAL
SHEAR MAY SUPPORT A BROKEN SQUALL LINE BENEATH DIFLUENT AND AT LEAST
WEAKLY DIVERGENT UPPER FLOW. DAMAGING WINDS AND LARGE HAIL ARE
EXPECTED TO BE THE PRIMARY SEVERE THREATS...BEFORE CONVECTION
WEAKENS THURSDAY EVENING.
..KERR.. 11/05/2008
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