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May 22, 2007 0600 UTC Day 1 Convective Outlook
Updated: Tue May 22 05:16:14 UTC 2007  (Print Version)
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
  | | |  
SPC Day 1 1200Z Wind prob outlook SPC Day1 1200Z Outlook Categorical Legend
 Forecast Discussion
   SPC AC 220512
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1212 AM CDT TUE MAY 22 2007
   
   VALID 221200Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT FROM
   SERN SD SWD INTO PORTIONS OF WRN AND CNTRL KS...
   
   ...SYNOPSIS...
   
   A SLOW EWD PROGRESSION OF WRN U.S. TROUGH IS FORECAST DURING THE DAY
   ONE PERIOD AS MAIN UPPER LOW OVER WRN MT/ID SHIFTS ENEWD INTO THE
   WRN DAKOTAS.  PRIMARY FEATURE OF INTEREST IN THIS BROADER SCALE
   TROUGH IS EMBEDDED SHORT WAVE TROUGH OR SPEED MAX OVER UT AS OF
   22/05Z.  THIS IMPULSE IS FORECAST TO EMERGE INTO THE CNTRL HIGH
   PLAINS THIS AFTERNOON...PRIOR TO EJECTING NEWD INTO THE UPPER MS
   VALLEY BY WEDNESDAY MORNING.
   
   IN THE LOW-LEVELS...NRN MOST SURFACE LOW OVER CNTRL SD IS EXPECTED
   TO DEVELOP NEWD ALONG COLD FRONT THROUGH THE RED RIVER VALLEY OF THE
   N INTO WRN ONTARIO.  MEANWHILE...SECONDARY SURFACE LOW DEVELOPING AT
   INTERSECTION OF COLD FRONT AND DRYLINE OVER NWRN KS WILL SHIFT
   GENERALLY SWD INTO THE OK/TX PNHDLS BY LATE TONIGHT.
   
   ...DAKOTAS AND NEB...
   
   COLD FRONT PUSHING EWD ACROSS THE REGION IS EXPECTED TO BE THE
   PRIMARY LOW-LEVEL FOCUS FOR STRONG TO POTENTIALLY SEVERE TSTM
   DEVELOPMENT THIS AFTERNOON INTO TONIGHT.  GOES SOUNDER DATA AND GPS
   PW PLOTS INDICATE THAT MOISTURE IS GRADUALLY INCREASING NWD THROUGH
   THE PLAINS...AND THIS TREND WILL CONTINUE TODAY AS THE ADVECTION
   PROCESS IS MAINTAINED BY 30-40 KT SLY LLJ.  THE STEEPEST MID-LEVEL
   LAPSE RATES /ASSOCIATED WITH ELEVATED MIXED LAYER/ ARE FORECAST TO
   RESIDE ALONG AND S OF MID-LEVEL JET...GENERALLY FROM CNTRL NEB SWD. 
   THESE STEEPER LAPSE RATES WILL CONTRIBUTE TO STRONGER INSTABILITY
   /MLCAPES OF 1500-2000 J PER KG/ BUT ALSO STRONGER CAPPING.  BOTH A
   WEAKER CAP AND INSTABILITY /MLCAPES OF 500-1000 J PER KG/ WILL
   EXTEND NWD INTO CNTRL/ERN SD BY AFTERNOON.
   
   TSTMS MAY BE ONGOING INITIALLY ACROSS THE CNTRL/ERN DAKOTAS...DRIVEN
   LARGELY BY WAA ALONG LLJ AXIS.  MORE VIGOROUS STORM DEVELOPMENT IS
   ANTICIPATED BY EARLY TO MID AFTERNOON ALONG FRONT OVER S-CNTRL SD
   WHERE SOME HEATING AND LOW-LEVEL MOISTURE INCREASE WILL ALLOW AIR
   MASS TO DESTABILIZE.  TSTMS SHOULD THEN DEVELOP SWD/SWWD ALONG COLD
   FRONT INTO WRN/CNTRL NEB THIS AFTERNOON AND EVENING.
   
   LARGELY PARALLEL ORIENTATION OF MID AND HIGH LEVEL WINDS TO SURFACE
   FRONT INDICATE A FAIRLY RAPID TRANSITION TO A CONVECTIVE LINE ACROSS
   SD INTO NRN NEB.  FARTHER S INTO CNTRL/SRN NEB...A STRONGER CAPPED
   ENVIRONMENT AND INCREASINGLY ZONAL MID AND HIGH LEVEL WIND COMPONENT
   SUGGESTS THE POTENTIAL FOR MORE OF A BROKEN LINE OR DISCRETE
   STORMS...SOME OF WHICH COULD BE SUPERCELLS GIVEN 35-40 KT OF DEEP
   LAYER SHEAR.  LARGE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY
   SEVERE THREATS...THOUGH A TORNADO OR TWO WILL BE POSSIBLE WITH ANY
   SUPERCELLS...ESPECIALLY OVER CNTRL/SRN NEB.
   
   OVER ND...ISOLATED HAIL AND/OR STRONG WIND GUSTS WILL ACCOMPANY THE
   MORE INTENSE STORMS DEVELOPING AHEAD OF FRONT. 
   HOWEVER...INSTABILITY APPEARS TO BE TOO LIMITED TO WARRANT A
   CATEGORICAL SLIGHT RISK.
   
   ...KS INTO THE ERN OK/TX PNHDLS AND WRN OK...
   
   DEWPOINTS IN THE LOWER/MID 60S COUPLED WITH STEEP LOW/MID-LEVEL
   LAPSE RATES ARE EXPECTED TO CONTRIBUTE TO A MODERATELY UNSTABLE AIR
   MASS LATER THIS AFTERNOON WITH MLCAPES INCREASING TO 1500-2500 J/KG.
   FORECAST SOUNDINGS SUGGEST THAT A WELL DEFINED EML WILL EFFECTIVELY
   CAP AIR MASS THROUGH MUCH OF DAY E OF DRYLINE.  AS MENTIONED IN THE
   ABOVE SECTION...DIURNAL STORM DEVELOPMENT IS EXPECTED TO OCCUR
   THROUGH THE AFTERNOON SWWD ALONG COLD FRONT OVER CNTRL/SRN
   NEB...EVENTUALLY INTO NWRN AND N-CNTRL KS BY LATE AFTERNOON OR EARLY
   EVENING.
   
   PRIMARY UNCERTAINTY IS HOW FAR S THE INITIATION AND SUSTENANCE OF
   DEEP MOIST CONVECTION WILL OCCUR.  22/00Z DETERMINISTIC AND 21/21Z
   ENSEMBLE MODEL DATA SUGGEST THAT THE COLD FRONT WILL THE PRIMARY
   LOCUS FOR STORM INITIATION WITH THE DRYLINE REMAINING LARGELY
   CAPPED.  AS SUCH...PROBABILISTIC AND CATEGORICAL FORECASTS HAVE BEEN
   ADJUSTED TO REFLECT THIS.
   
   DESPITE SOME RELATIVE WEAKNESS IN HIGH-LEVEL WIND FIELDS...OVERALL
   HODOGRAPH SHAPE OVER WRN/CNTRL KS APPEARS TO BE QUITE SUPPORTIVE OF
   SUPERCELLS GIVEN THE DEGREE OF INSTABILITY WITH THE PRIMARY SEVERE
   THREATS BEING LARGE HAIL /SOME POTENTIALLY SIGNIFICANT/...HIGH WINDS
   AND A FEW TORNADOES.  THIS IS ESPECIALLY THE CASE FOR SWRN-MOST OR
   ANCHOR STORMS ALONG COLD FRONT AND IF ANY STORMS CAN BECOME
   ESTABLISHED ALONG DRYLINE.
   
   OVER THE OK/TX PNHDLS INTO WRN OK...STORM INITIATION APPEARS MUCH
   LESS PROBABLE.  SHOULD AN ISOLATED STORM DEVELOP...ENVIRONMENT WOULD
   BE SUPPORTIVE OF UPDRAFT ROTATION WITH A THREAT OF LARGE HAIL AND
   PERHAPS A TORNADO.
   
   ...ERN TX...
   
   A MOIST AND MODERATELY UNSTABLE AIR MASS WILL EXIST TODAY IN WAKE OF
   MID-LEVEL IMPULSE LIFTING NEWD TOWARD THE ARKLATEX.  POTENTIAL WILL
   EXIST FOR AN MCV TO DEVELOP FROM MCS ONGOING NOW OVER THE EDWARDS
   PLATEAU...WITH THIS FEATURE FOCUSING DIURNAL STORM DEVELOPMENT THIS
   AFTERNOON /SIMILAR TO MONDAY/.  GIVEN THE MOIST BOUNDARY LAYER
   CONDITIONS AND MODEST LOW-LEVEL SHEAR...A TORNADO OR TWO IS POSSIBLE
   WITH ANY ROTATING STORMS...ALONG WITH THE POSSIBILITY OF LOCALLY
   STRONG WIND GUSTS.
   
   ..MEAD/TAYLOR.. 05/22/2007
   
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Page last modified: May 22, 2007
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