Mar 21, 2007 1630 UTC Day 1 Convective Outlook
Updated: Wed Mar 21 16:36:15 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Categorical Graphic
20070321 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20070321 1630 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20070321 1630 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20070321 1630 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 211632
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1132 AM CDT WED MAR 21 2007
   
   VALID 211630Z - 221200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER
   MIDWEST...CENTRAL AND SRN PLAINS...
   
   ...SYNOPSIS...
   SPLIT FLOW PATTERN IS EVIDENT OVER THE WRN STATES WITH A STRONG
   SHORT WAVE TROUGH IN THE NRN BRANCH OF THE WESTERLIES FROM THE
   CANADIAN PRAIRIES INTO MT...AND A DEVELOPING CUT-OFF LOW OVER THE
   GREAT BASIN.  THE NRN SHORT WAVE IS FORECAST TO CONTINUE RAPIDLY EWD
   ACROSS THE NRN PLAINS REACHING THE UPPER MS VALLEY LATE TONIGHT
   WHILE THE CUT-OFF LOW DEVELOPS SWD OFF THE NRN BAJA COAST. 
   DOWNSTREAM OVER THE PLAINS/UPPER MS VALLEY THERE ARE SEVERAL WEAK
   PERTURBATIONS IN THE MID/UPPER LEVELS MOVING ENEWD.
   
   AT THE SURFACE...THE NRN PART OF A STRONG COLD FRONT CURRENTLY
   LOCATED FROM THE ERN ND/NWRN MN BORDER SEWD INTO CENTRAL NEB INTO
   CENTRAL CO WILL MOVE RAPIDLY EWD...WHILE THE SRN PART OF THE FRONT
   MOVES MORE SLOWLY SEWD. THE FRONT IS FORECAST TO EXTEND BY 00Z FROM
   WRN LAKE SUPERIOR AND NWRN IA/S CNTRL NEB INTO A LOW ALONG THE
   KS/NEB BORDER THEN CONTINUING INTO CENTRAL CO...AND IS EXPECTED TO
   REACH A LOWER MI/NRN IL/NRN MO/SWRN KS LINE BY THE END OF THE
   PERIOD.  A DRY LINE OVER THE HIGH PLAINS WILL MOVE EWD INTO CENTRAL
   KS AND THE TX SOUTH PLAINS BY THIS EVENING.
   
   ...CENTRAL AND ERN IA/NRN MO/NWRN IL...
   ELEVATED STRONG/SEVERE STORMS ARE CONTINUING TO SPREAD EWD ACROSS
   SOUTH CENTRAL/SERN IA IN ADVANCE OF MID/UPPER LEVEL SHORT WAVE
   TROUGH MOVING ACROSS THE LOWER MO RIVER VALLEY.  PLUME OF STEEP
   ELEVATED LAPSE RATES ABOVE 700 MB IS ENHANCING UPDRAFT INTENSITY. 
   DIURNAL HEATING WILL BE STRONGER OVER NRN MO INTO SERN IA WHERE
   SATELLITE INDICATES LIMITED CLOUDS IN ADVANCE OF THE
   CONVECTION...WITH POTENTIAL FOR STORMS TO INCREASE OVER NRN MO/SERN
   IA AND BECOME NEAR-SURFACE BASED DURING THE AFTERNOON.  STRONGER
   CELLS WILL BE CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND
   GUSTS INTO THE EVENING.
   
   ...SOUTH CENTRAL AND ERN NEB/N CENTRAL/NERN KS/IA...
   MOISTURE IS INCREASING NWD OVER THE CENTRAL PLAINS AND LOWER MO
   VALLEY WITH SURFACE DEW POINTS CURRENTLY NEAR 60F.  COOL MID LEVEL
   TEMPERATURES/STEEP LAPSE RATES ABOVE A STRONG CAPPING INVERSION IN
   THE 800-750 MB LAYER WILL CONTRIBUTE TO A MODERATELY UNSTABLE
   ENVIRONMENT WITH MLCAPE OF 1500-2500 J/KG.  HOWEVER...THE CAP WILL
   LIKELY INHIBIT CONVECTIVE DEVELOPMENT IN THE WARM SECTOR THROUGH AT
   LEAST MID AFTERNOON.  ALTHOUGH DYNAMIC FORCING FOR LARGE SCALE
   ASCENT APPEARS TO BE MODEST AT BEST...LOW LEVEL CONVERGENCE ALONG
   THE ADVANCING COLD FRONT AND DRY LINE IS EXPECTED TO BE SUFFICIENT
   FOR CONVECTIVE INITIATION TO OCCUR BY LATE AFTERNOON OR
   EVENING...ESPECIALLY INVOF THE TRIPLE POINT NEAR THE KS/NEB BORDER. 
   MODEL GUIDANCE INCLUDING HIGH RESOLUTION WRF MODELS INDICATE STORMS
   WILL DEVELOP OVER PARTS OF ERN NEB INTO NORTH CENTRAL KS BY LATE
   AFTERNOON OR EVENING.  GIVEN THE FAVORABLE INSTABILITY AND
   SUFFICIENT DEEP LAYER SHEAR /35-40 KT IN THE LOWEST 6 KM/...A FEW
   SUPERCELLS ARE LIKELY TO DEVELOP WITH ATTENDANT THREAT FOR ISOLATED
   TORNADOES IN ADDITION TO LARGE HAIL AND DAMAGING WIND GUSTS.  AS THE
   EVENING PROGRESSES CONVECTIVE MODE MAY TRANSITION INTO LINE SEGMENTS
   ALONG THE COLD FRONT AS IT MOVES EWD AND SEWD INTO THE LOW LEVEL
   MOISTURE AND INSTABILITY AXIS.  A THREAT FOR DAMAGING WIND GUSTS AND
   ISOLATED HAIL MAY PERSIST INTO THE OVERNIGHT HOURS.
   
   ...REMAINDER OF KS SWD INTO WRN TX...
   STRONG HEATING IS EXPECTED TO OCCUR ALONG THE DRY LINE FROM KS SWWD
   INTO SWRN TX WHICH WILL CONTRIBUTE TO MLCAPE OF 1500-2000 J/KG. 
   WEAK CONVERGENCE ALONG THE DRY LINE COUPLED WITH LOW LEVEL HEATING
   MAY WEAKEN THE CAP SUFFICIENTLY FOR ISOLATED CONVECTION TO DEVELOP
   LATE THIS AFTERNOON AND EVENING.  MOST FAVORABLE DEEP LAYER SHEAR
   FOR ORGANIZED STORMS WILL BE OVER CENTRAL KS AND ESPECIALLY FROM THE
   TX SOUTH PLAINS SWD INTO THE TRANSPECOS REGION...SUGGESTING
   SUPERCELLS WILL BE POSSIBLE IN THESE AREAS.
   
   ..WEISS/JEWELL.. 03/21/2007
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z