Feb 28, 2007 0600 UTC Day 1 Convective Outlook
Updated: Wed Feb 28 06:08:11 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Categorical Graphic
20070228 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20070228 1200 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20070228 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20070228 1200 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 280603
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1203 AM CST WED FEB 28 2007
   
   VALID 281200Z - 011200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN KS/ERN OK EWD INTO THE
   MID MO VALLEY...
   
   ...SYNOPSIS...
   LARGE UPPER TROUGH OVER THE WRN CONUS WILL SHIFT EWD AND TAKE ON AN
   INCREASINGLY-NEGATIVE TILT...AS STRONG/EMBEDDED SHORT-WAVE FEATURE
   SHIFTS QUICKLY EWD ACROSS THE FOUR CORNERS REGION AND INTO THE
   CENTRAL PLAINS AND VICINITY LATE.  THIS TROUGH WILL BE ACCOMPANIED
   BY A BROAD/STRONG MID-LEVEL JET STREAK WHICH WILL SPREAD ACROSS THE
   CENTRAL AND SRN PLAINS -- PARTICULARLY DURING THE SECOND HALF OF THE
   PERIOD.
   
   AT THE SURFACE...CYCLOGENESIS SHOULD BE UNDERWAY AT THE START OF THE
   PERIOD OVER SERN CO...WITH THE LOW FORECAST TO DEEPEN WHILE ARCING
   CYCLONICALLY EWD/NEWD TO NRN MO BY THE END OF THE PERIOD.  A DRYLINE
   IS FORECAST TO SHARPEN/MOVE EWD ACROSS WRN OK/N TX THROUGH THE
   AFTERNOON...AND WILL EVENTUALLY BE OVERTAKEN BY THE COLD FRONT AS IT
   SWEEPS ACROSS OK/TX LATE IN THE PERIOD.
   
   ...ERN KS/ERN OK/NERN TX EWD TO THE MID MO VALLEY...
   DIFFICULT-TO-FORECAST EVENT IS UNFOLDING THIS PERIOD FROM ERN
   PORTIONS OF THE CENTRAL AND SRN PLAINS EWD TO THE MS VALLEY...WITH
   STRONG/NEGATIVELY-TILTED UPPER TROUGH AND ASSOCIATED CYCLOGENESIS
   FORECAST TO SHIFT EWD INTO THIS REGION...ACCOMPANIED BY VERY STRONG
   KINEMATICS.  HOWEVER...DESPITE WHAT AT FIRST GLANCE APPEARS TO BE A
   VERY FAVORABLE SETUP FOR A SIGNIFICANT SEVERE WEATHER EPISODE...THE
   SCENARIO IS COMPLICATED BY QUESTIONS REGARDING QUALITY OF MOISTURE
   RETURN...AS WELL AS FAIRLY SUBSTANTIAL CAPPING FORECAST AT THE BASE
   OF AN ELEVATED MIXED-LAYER.
   
   ATTM...IT APPEARS THAT ELEVATED CONVECTION SHOULD BE
   ONGOING/INCREASING ACROSS THE MID MO VALLEY REGION...WITHIN ZONE OF
   STRONG WARM ADVECTION ASSOCIATED WITH 50 KT LOW-LEVEL JET. 
   POTENTIAL FOR HAIL MAY ACCOMPANY THESE STORMS THROUGH THE DAY AS
   CONVECTION EXPANDS ACROSS IA/IL/NERN AND ERN MO.
   
   MEANWHILE...DRYLINE SHOULD BE SHIFTING EWD ACROSS THE WRN HALF OF OK
   AND WRN N TX THROUGH THE AFTERNOON...AS STRONG/DEEP MIXING OCCURS. 
   THOUGH HIGH-LEVEL CLOUDINESS SHOULD INHIBIT HEATING TO SOME DEGREE
   -- AND THUS MAY SLOW THE EWD ADVANCE OF THE DRYLINE...IT APPEARS
   THAT THE DRYLINE SHOULD EXTEND ROUGHLY ALONG THE I35 CORRIDOR BY
   LATE AFTERNOON.
   
   AHEAD OF THE DRYLINE...BOUNDARY-LAYER MOISTURE WILL CONTINUE
   ADVECTING NWD ON SLY LOW-LEVEL FLOW...WITH MID TO UPPER 50S
   DEWPOINTS SPREADING INTO ERN KS/SRN AND WRN MO AND LOW 60S CROSSING
   THE RED RIVER BY 01/00Z.  THIS WILL RESULT IN THE DEVELOPMENT OF 500
   TO 1000 J/KG MEAN-LAYER CAPE THROUGH THE AFTERNOON ACROSS THE THREAT
   AREA.  WHILE IT APPEARS ATTM THAT CAP WILL SUPPRESS CONVECTIVE
   DEVELOPMENT IN MOST AREAS...EXPECT A FEW STORMS TO INITIATE FROM
   NEAR THE LOW/WARM FRONT ACROSS SRN AND ERN KS SWD ALONG THE DRYLINE.
    AS THETA-E ADVECTION CONTINUES/INCREASES OVERNIGHT WITH THE
   RE-DEVELOPMENT OF THE LOW-LEVEL JET...STORMS SHOULD INCREASE
   SOMEWHAT IN COVERAGE THROUGH THE EVENING -- MAINLY FROM ERN KS/ERN
   OK INTO MO AND AR.  HOWEVER...OVERALL COVERAGE OF STORMS SHOULD
   REMAIN LIMITED AS GENERAL CAPPING PERSISTS IN THE FREE WARM SECTOR.
   
   THOUGH STORMS WILL BE INCREASINGLY-ELEVATED WITH NEWD EXTENT ACROSS
   MO...SURFACE-BASED STORMS SHOULD EXTEND AT LEAST AS FAR N AS CENTRAL
   MO BY LATE IN THE PERIOD AS LOW-LEVEL UVV/MIXING INCREASE.  
   
   DESPITE THE QUESTIONS REGARDING STORM COVERAGE...VERY STRONG FLOW
   VEERING WITH HEIGHT WILL SUPPORT LONG-LIVED/ROTATING UPDRAFTS WITH
   ANY STORMS WHICH CAN DEVELOP.  ALONG WITH SOME POTENTIAL FOR
   LOCALLY-DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES WILL ALSO
   BE POSSIBLE.  GIVEN WIDESPREAD AREA OF VERY STRONG SHEAR...A COUPLE
   OF SIGNIFICANT TORNADOES CANNOT BE RULED OUT ANYWHERE FROM ERN
   OK/ERN KS DURING THE AFTERNOON INTO MO/AR THROUGH THE OVERNIGHT
   HOURS.  ATTM...WILL NOT INTRODUCE A MODERATE RISK...BUT THE
   POTENTIAL FOR AT LEAST A FEW SIGNIFICANT SUPERCELLS IS EVIDENT. 
   SHOULD IT APPEAR THAT STORM COVERAGE WILL BE GREATER THAN CURRENTLY
   ANTICIPATED...AN UPGRADE TO MODERATE RISK WOULD BE LIKELY.
   
   ..GOSS.. 02/28/2007
   
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