SPC AC 232000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT MON APR 23 2007
VALID 232000Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND TONIGHT
ACROSS PARTS OF THE ERN TX PNHDL...NW OK...WRN KS...ERN CO AND PARTS
OF SW NEB....
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...ACROSS MUCH OF THE CNTRL/SRN HIGH PLAINS....
...CENTRAL/SOUTHERN PLAINS...
SOUTHERN BRANCH TROUGH REMAINS OVER THE INTERMOUNTAIN WEST...WITH A
NEW CLOSED LOW NOW DEVELOPING ACROSS PARTS OF THE SOUTHERN GREAT
BASIN. THIS IS OCCURRING IN RESPONSE TO STRONGER MID/UPPER JET
CORE...WHICH IS JUST NOW NOSING ACROSS SOUTHERN CALIFORNIA/ARIZONA.
MODELS SUGGEST THAT THIS FEATURE WILL EVENTUALLY DEVELOP AROUND THE
SOUTHERN/EASTERN PERIPHERY OF THE MID-LEVEL CIRCULATION...INTO THE
SOUTHERN/CENTRAL HIGH PLAINS...BUT THIS WILL NOT OCCUR UNTIL LATER
TONIGHT INTO EARLY TUESDAY.
HOWEVER...BROADER SCALE DIFLUENT/DIVERGENT UPPER FLOW REGIME
DOWNSTREAM OF SOUTHERN BRANCH TROUGH ALREADY EXTENDS ACROSS THE
CENTRAL/SOUTHERN HIGH PLAINS...WHERE A MOIST RETURN FLOW OFF THE
GULF OF MEXICO IS UNDERWAY. SOUTH/SOUTHWESTERLY MID-LEVEL
FLOW...ABOVE SLOWLY STRENGTHENING SOUTHERLY LOW-LEVEL FLOW...IS ALSO
ALREADY OF SUFFICIENT STRENGTH TO SUPPORT FAVORABLE DEEP LAYER SHEAR
FOR SUPERCELL DEVELOPMENT...AND THIS WILL IMPROVE THROUGH THE LATE
AFTERNOON AND EVENING HOURS. IN CONJUNCTION WITH ONGOING
DESTABILIZATION...POTENTIAL FOR SEVERE THUNDERSTORMS IS INCREASING
ACROSS MUCH OF THE CENTRAL/SOUTHERN HIGH PLAINS.
INHIBITION ASSOCIATED WITH A WARM LOWER/MID TROPOSPHERE IS
CONSIDERABLE ACROSS THE SOUTHERN PLAINS. BUT...A WEAK SUBTROPICAL
IMPULSE NOW PROGRESSING ACROSS WESTERN TEXAS MAY SUPPRESS THIS A
BIT. AND...IN CONJUNCTION WITH CONFLUENT LOW-LEVEL FLOW AND
LOW-LEVEL WARM ADVECTION...CAP MAY WEAKEN ENOUGH FOR AT LEAST
SCATTERED STORMS BY LATE AFTERNOON. FORCING SEEMS LIKELY TO FOCUS
DEVELOPMENT FROM PARTS OF WESTERN OKLAHOMA AND THE EASTERN TEXAS
PANHANDLE INTO SOUTHWEST KANSAS...WHERE RETURN OF 60F+ DEW POINTS
AND STEEPENING LAPSE RATES WILL CONTRIBUTE TO MIXED LAYER CAPE AS
HIGH AS 2000 J/KG. A FEW SUPERCELLS ARE LIKELY...WITH POTENTIAL FOR
VERY LARGE HAIL/ISOLATED DAMAGING WIND GUSTS. TORNADOES ARE ALSO
POSSIBLE...PARTICULARLY AS LOW-LEVEL SHEAR PROFILES BECOME ENHANCED
BENEATH STRENGTHENING LOW-LEVEL JET BY THE 24/00-02Z TIME FRAME.
FAVORABLE OROGRAPHY MAY AID ADDITIONAL CONVECTIVE DEVELOPMENT LATE
THIS AFTERNOON TO THE LEE OF THE COLORADO FRONT RANGE...WHERE
SIGNIFICANT DESTABILIZATION HAS YET TO OCCUR. HOWEVER...THE
BOUNDARY LAYER IS MOISTENING ON SOUTHEASTERLY UPSLOPE FLOW...AND A
FEW SUPERCELLS SEEM LIKELY WITH POTENTIAL FOR LARGE HAIL/DAMAGING
WIND GUSTS...PERHAPS BRIEF TORNADOES.
LATER THIS EVENING...INCREASING INHIBITION WITH THE LOSS OF DAYTIME
HEATING MAY SUPPRESS SOUTHERN HIGH PLAINS ACTIVITY...BUT STORMS SEEM
LIKELY TO INCREASE IN COVERAGE AND MAINTAIN OR INCREASE IN INTENSITY
ACROSS PARTS OF EASTERN COLORADO INTO WESTERN KANSAS. THIS WILL
OCCUR AS MID/UPPER FORCING FOR UPWARD VERTICAL MOTION STRENGTHENS
WITH THE APPROACH OF THE UPPER JET...AND MOIST RETURN FLOW
CONTINUES. TRENDS ARE EXPECTED FOR MUCH OF THE CONVECTION TO BECOME
BASED ABOVE A WARM FRONTAL INVERSION LAYER...WITH LARGE HAIL
BECOMING THE PRIMARY SEVERE THREAT BEFORE ACTIVITY CONTINUES TO
SPREAD NORTHWARD INTO NEBRASKA OVERNIGHT.
...OHIO VALLEY...
IN THE WAKE OF SHORT WAVE TROUGH NOW ACCELERATING INTO THE LOWER
GREAT LAKES/ST. LAWRENCE VALLEY...A TRAILING LOW/MID-LEVEL
CONFLUENCE ZONE MAY STILL BECOME THE FOCUS FOR THUNDERSTORM
ACTIVITY. LAPSE RATES ACROSS THIS REGION ARE WEAK...BUT A HEATED
MOIST BOUNDARY WITH SIZABLE TEMPERATURE/DEW POINTS SPREADS AND 40+
KT MEAN ENVIRONMENTAL FLOW WILL PROVIDE POTENTIAL FOR GUSTY WINDS
NEAR ANY STORMS THAT DO DEVELOP...THROUGH MID EVENING.
..KERR.. 04/23/2007
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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