ACUS02 KWNS 161730
SWODY2
SPC AC 161728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT TUE OCT 16 2007
VALID 171200Z - 181200Z
..THERE IS A MDT RISK OF SVR TSTMS WED AFTN/EVE ACROSS MUCH OF
CNTRL/ERN KS AND OK INTO PARTS OF WRN MO/AR....
..THERE IS A SLGT RISK OF SVR TSTMS WED/WED NIGHT SURROUNDING THE
MDT RISK AREA...ACROSS THE CNTRL/SRN PLAINS INTO THE MID MS VLY....
..SYNOPSIS...
THE NOSE OF A VERY STRONG WEST NORTHWESTERLY UPPER JET STREAK OVER
THE EASTERN PACIFIC IS NOW OVERSPREADING CALIFORNIA...AND PROGGED TO
CONTINUE THROUGH THE SOUTHERN ROCKIES BY 12Z WEDNESDAY...AND THE
MIDDLE/LOWER MISSISSIPPI VALLEY BY 12Z THURSDAY. MUCH OF MODEL
GUIDANCE INDICATES THAT...AS THIS OCCURS...STRONG SURFACE
CYCLOGENESIS WILL TAKE PLACE TO THE LEE OF THE CENTRAL ROCKIES...
WITH THE MAIN SURFACE LOW LIKELY TO LIFT OUT OF THE CENTRAL PLAINS
THROUGH THE MIDDLE MISSOURI VALLEY BY LATE WEDNESDAY NIGHT/EARLY
THURSDAY. THIS WILL SUPPORT A NORTHWARD RETURN FLOW OF MOISTURE
FROM THE SOUTHERN PLAINS/RIO GRANDE VALLEY.
RICHER BOUNDARY LAYER MOISTURE OVER THE WESTERN GULF OF
MEXICO...CHARACTERIZED BY LOWER/MID 70S DEW POINTS...WILL PROBABLY
NOT BECOME ENTRAINED INTO THE DEVELOPING SYSTEM OVER THE PLAINS.
BUT...THIS MOISTURE IS EXPECTED TO ADVECT TOWARD THE LOWER
MISSISSIPPI VALLEY/CENTRAL AND EASTERN GULF COAST REGION...AS A
TROPICAL PERTURBATION NOW OVER THE WESTERN GULF OF MEXICO
ACCELERATES NORTH NORTHEASTWARD...AHEAD OF THE DEVELOPING SOUTH
CENTRAL PLAINS POLAR TROUGH.
THE FIRST IN A SERIES OF IMPULSES EMBEDDED WITHIN THE POLAR JET IS
PROGGED EAST OF THE SOUTHERN ROCKIES INTO THE SOUTHERN PLAINS LATE
TONIGHT INTO EARLY WEDNESDAY. AND...AMPLIFICATION OF A LARGER SCALE
TROUGH WILL CONTINUE THROUGH THE REMAINDER OF THE PERIOD AS A MORE
SIGNIFICANT IMPULSE/JETLET DIGS TO THE LEE OF THE CENTRAL/ SOUTHERN
ROCKIES.
..CENTRAL/SOUTHERN PLAINS INTO THE MID MISSISSIPPI VALLEY...
POTENTIAL FOR AN OUTBREAK OF SEVERE STORMS DOES EXIST FOR
WEDNESDAY...INCLUDING THE POSSIBILITY OF ISOLATED STRONG TORNADOES.
MOISTURE RETURN AND LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION
WITH INITIAL IMPULSE ARE EXPECTED TO SUPPORT A RAPID INCREASE IN
CONVECTIVE DEVELOPMENT EARLY IN THE PERIOD...PARTICULARLY FROM PARTS
OF THE SOUTH CENTRAL PLAINS THROUGH THE OZARK PLATEAU REGION. MUCH
OF THIS ACTIVITY LIKELY WILL BE ELEVATED ABOVE A LINGERING
COOL/STABLE LOW-LEVEL ENVIRONMENT ASSOCIATED WITH A WEAKENING LOW/
MID-LEVEL CYCLONE NOW LIFTING NORTHEAST OF THE MID MISSOURI VALLEY.
SOME OF THESE STORMS...MAINLY WHERE STRONGER MID-LEVEL COOLING
CONTRIBUTES TO STEEPER MID-LEVEL LAPSE RATES ACROSS THE SOUTH
CENTRAL PLAINS...COULD CONTAIN SOME LARGE HAIL. HOWEVER...THIS
THREAT MAY DIMINISH AS CONVECTION/CLOUDS AND PRECIPITATION BECOME
INCREASINGLY WIDESPREAD AND DEVELOP NORTHEASTWARD/EASTWARD THROUGH
THE DAY.
THE PROSPECT FOR CONSIDERABLE EARLY CONVECTION...IN CONJUNCTION WITH
LOWER SUN ANGLE/SEASONABLY WEAKER DAYTIME HEATING...PROVIDE
UNCERTAINTY REGARDING THE MAGNITUDE AND EXTENT OF SEVERE THREAT
LATER WEDNESDAY...AND PARTICULARLY WEDNESDAY EVENING/NIGHT.
HOWEVER...IT APPEARS LIKELY THAT A LEAST A NARROW CORRIDOR OF
SURFACE HEATING WILL OCCUR ALONG/JUST EAST OF A DRY LINE EXPECTED TO
CURVE SOUTHEAST/SOUTH OF A DEEPENING SURFACE LOW OVER WESTERN KANSAS
BY 21Z WEDNESDAY. IN THE PRESENCE OF STEEP LAPSE RATES BENEATH A
MID-LEVEL THERMAL TROUGH...MODELS ARE SUGGESTIVE THAT MIXED LAYER
CAPE WILL EXCEED 1000 J/KG...AND THERMODYNAMIC PROFILES WILL BE
CONDUCIVE TO STRONG UPDRAFTS. COUPLED WITH STRONG DEEP LAYER NEAR A
90+ KT WESTERLY 500 MB JET STREAK...THE ENVIRONMENT WILL BE
FAVORABLE FOR SUPERCELLS WITH VERY LARGE HAIL/ LOCALIZED DAMAGING
WINDS. AND...LARGE LOW-LEVEL HODOGRAPHS BENEATH A 40-50+ KT
SOUTHERLY 850 MB JET WILL SUPPORT THE RISK FOR A FEW
TORNADOES...SOME OF WHICH COULD BECOME STRONG ACROSS PARTS OF
CENTRAL/EASTERN KANSAS AND OKLAHOMA.
SEVERE THREAT WILL CONTINUE AT LEAST INTO EARLY EVENING. AND... IF
DESTABILIZATION IS NOT SUBSTANTIALLY IMPEDED BY EARLIER
CONVECTION...SEVERE POTENTIAL COULD CONTINUE NORTHEASTWARD THROUGH
THE MIDDLE MISSISSIPPI VALLEY WEDNESDAY NIGHT. BUT...AGAIN...THIS
IS HIGHLY UNCERTAIN AT THE PRESENT TIME.
..LOWER MS VALLEY/TN VALLEY AND ERN GULF STATES...
UNCERTAINTY ALSO EXISTS...BUT A SEVERE THREAT COULD ACCOMPANY A
LINGERING LOW/MID-LEVEL CIRCULATION LIFTING INLAND OUT OF THE
WESTERN GULF OF MEXICO. INSTABILITY WILL LIKELY BE LIMITED DUE TO
WEAK LAPSE RATES...BUT INLAND ADVECTION OF A MOIST BOUNDARY LAYER
WITH 70F+ DEW POINTS AND STRENGTHENING LOW-LEVEL WIND FIELDS/SHEAR
COULD SUPPORT THE RISK FOR ISOLATED TORNADOES/DAMAGING WINDS.
.KERR.. 10/16/2007
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