Mar 21, 2007 2000 UTC Day 1 Convective Outlook
Updated: Wed Mar 21 20:02:14 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Categorical Graphic
20070321 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20070321 2000 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20070321 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20070321 2000 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 211958
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0258 PM CDT WED MAR 21 2007
   
   VALID 212000Z - 221200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE LWR/MID MO
   VALLEY INTO THE UPPER GREAT LAKES...AND ACROSS THE CNTRL/SRN HIGH
   PLAINS....
   
   ...LWR/MID MO VALLEY INTO THE UPPER GREAT LAKES REGION...
   AS THE CLOSED LOW...NOW DEVELOPING NEAR THE SOUTHERN CALIFORNIA
   COAST...BECOMES INCREASINGLY CUT-OFF LATER TODAY/TONIGHT...AND THE
   VIGOROUS NORTHERN BRANCH IMPULSE PROGRESSES EASTWARD ALONG THE
   CENTRAL CANADIAN/U.S. BORDER AREA...THE UPPER PATTERN IS EXPECTED TO
   TREND TOWARD A MORE ZONAL SPLIT FLOW REGIME.  UNTIL THIS OCCURS
   ...THE PATTERN REMAINS AMPLIFIED...WITH A WEAK SOUTHWESTERLY BELT OF
   FLOW EMANATING FROM THE SOUTHERN PLATEAU AREA EXTENDING THROUGH THE
   GREAT LAKES.  BROAD...LOW AMPLITUDE TROUGHING WITH SMALLER SCALE
   IMPULSES...EMBEDDED WITHIN THIS REGIME...CONTINUES TO GRADUALLY LIFT
   INTO THE GREAT LAKES.  THIS FEATURE IS PROVIDING THE SUPPORT FOR THE
   PRIMARY ONGOING /AS OF 20Z/ CONVECTIVE DEVELOPMENT...WHICH IS
   OCCURRING ON THE EASTERN FRINGE OF ELEVATED MIXED LAYER AIR WHICH
   HAS SPREAD EAST OF THE PLATEAU/ROCKIES THROUGH MUCH OF THE PLAINS.
   
   WHILE LOW-LEVEL WARMING/MOISTENING CONTINUES AHEAD OF SURFACE COLD
   FRONT ALREADY NOSING TO THE LEE OF THE NORTHERN/CENTRAL ROCKIES
   ...IT IS THE INHIBITION ASSOCIATED WITH WARMING ALOFT THAT IS
   CONTRIBUTING TO UNCERTAIN CONVECTIVE POTENTIAL LATE THIS AFTERNOON. 
   IT STILL APPEARS PROBABLE THAT SUBSTANTIAL CONVECTIVE DEVELOPMENT
   WILL OCCUR IN RESPONSE TO FORCING ASSOCIATED WITH NORTHERN BRANCH
   TROUGH.  HOWEVER...TIMING OF INITIATION IS UNCLEAR.
   
   THE DRY LINE/COLD FRONT INTERSECTION SEEMS TO BE THE MOST LIKELY
   LOCATION OF STRONG CONVECTIVE INITIATION...SOMEWHERE ACROSS
   SOUTHEAST NEBRASKA/NORTH CENTRAL OR NORTHEAST KANSAS.  BUT THIS MAY
   NOT OCCUR UNTIL CLOSER TO 22/00Z.  ONCE CAP BREAKS...MIXED LAYER
   CAPE AT OR ABOVE 1000 J/KG WILL BE SUPPORTIVE OF VIGOROUS UPDRAFTS. 
   ALTHOUGH FLOW NEAR/ABOVE 500 MB IS RELATIVELY MARGINAL...MODERATELY
   STRONG WINDS...VEERING WITH HEIGHT...IN THE 850 TO 700 MB LAYER
   PROBABLY WILL BE SUFFICIENT FOR UPDRAFT ROTATION.  LARGE HAIL AND
   ISOLATED DOWNBURSTS ARE EXPECTED TO BE PRIMARY THREAT WITH THIS
   ACTIVITY.
   
   LATER IN THE EVENING...INTO THE OVERNIGHT HOURS...A CONVECTIVE LINE
   MAY DEVELOP ALONG/AHEAD OF COLD FRONT ACROSS THE MID MISSOURI
   VALLEY...EASTWARD THROUGH UPPER PORTIONS OF THE MIDDLE MISSISSIPPI
   VALLEY.  DAMAGE WIND GUSTS SHOULD BECOME THE MORE PREDOMINANT
   THREAT...PARTICULARLY WITH ACTIVITY IN CLOSER PROXIMITY TO BETTER
   CONVECTIVE INSTABILITY...SPREADING SOUTHEASTWARD THROUGH THE MIDDLE
   TO LOWER MISSOURI VALLEY.
   
   ...SOUTHERN PLAINS...
   CONVECTIVE DEVELOPMENT IS EXPECTED TO BE MUCH MORE SPARSE ALONG DRY
   LINE EXTENDING SOUTHWARD THROUGH THE HIGH PLAINS.  BEST CHANCE FOR
   ISOLATED STORMS MAY BE NEAR MID/UPPER JET AXIS ACROSS THE EASTERN
   TEXAS PANHANDLE/NORTHWEST TEXAS.  GIVEN FAVORABLE
   CONDITIONAL/CONVECTIVE INSTABILITY...DEEP LAYER SHEAR APPEARS
   MARGINALLY FAVORABLE FOR SUPERCELLS WITH HAIL/GUSTY WINDS.
   
   ...GREAT BASIN...
   FORCING/DESTABILIZATION NORTHEAST OF AN INITIAL SOUTHERN BRANCH
   MID-LEVEL CIRCULATION HAS SUPPORTED RECENT FORMATION OF STORMS
   ACROSS THE EASTERN GREAT BASIN.  MODERATELY STRONG DEEP LAYER
   SHEAR...COOL MID-LEVEL AIR MASS AND DEEPENING MIXED BOUNDARY LAYER
   AHEAD OF ASSOCIATED COLD FRONT COULD SUPPORT RISK FOR SOME
   HAIL/GUSTY WINDS IN STRONGER CELLS THIS AFTERNOON.
   
   ..KERR.. 03/21/2007
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z