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    Day 2 Outlook >
Mar 8, 2013 2000 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Fri Mar 8 21:13:43 UTC 2013  (Print Version)
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 Forecast Discussion
   SPC AC 081931
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0131 PM CST FRI MAR 08 2013
   
   VALID 082000Z - 091200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN HIGH PLAINS
   REGION...
   
   ...DISCUSSION...
   LITTLE CHANGE APPEARS NECESSARY TO THE ONGOING FORECAST...WITH
   LATEST DATA SUGGESTING THAT CURRENT EXPECTATIONS REMAIN ON TRACK. 
   THE ONLY CHANGE INSERTED THIS FORECAST WILL BE INCLUSION OF A
   MARGINAL /5% PROBABILITY/ FOR HAIL POSSIBLY APPROACHING SEVERE
   LEVELS IN A STRONGER CELL OR TWO THIS AFTERNOON ACROSS SRN AZ JUST
   AHEAD OF THE UPPER LOW APPROACHING SRN CA ATTM.  FOR ADDITIONAL
   SHORT-TERM INFORMATION ON THIS AREA...PLEASE REFER TO SWOMCD #0251.
   
   ..GOSS.. 03/08/2013
   
   .PREV DISCUSSION... /ISSUED 1046 AM CST FRI MAR 08 2013/
   
   CORRECTED FOR NDFD GRID GENERATION
   
   ...SYNOPSIS...
   UPPER-AIR PATTERN ACROSS CONUS IS DOMINATED BY TWO PRIMARY CYCLONES
   -- ONE OVER ATLC S OF NOVA SCOTIA WITH STG VORTICITY LOBE EXTENDING
   WWD OVER MID-ATLC REGION...AND ANOTHER LOCATED OVER CHANNEL ISLANDS
   AREA OFFSHORE SRN CA.  AS MID-ATLC PERTURBATION MOVES
   OFFSHORE...SYNOPTIC-SCALE RIDGING WILL SHIFT EWD ACROSS MS VALLEY TO
   UPPER GREAT LAKES...LOWER OH VALLEY AND TN VALLEY REGIONS. 
   MEANWHILE...MAIN PAC LOW WILL TURN EWD ACROSS SRN CA...REACHING NEAR
   AZ/NM BORDER BY END OF PERIOD.  BROAD BELT OF CYCLONIC FLOW --
   INCLUDING ROUGHLY 120-KT 250-MB JET MAX AND ELONGATED RIBBON OF
   80-90 KT 500-MB WINDS -- WILL SHIFT EWD OVER PORTIONS SRN AZ AND NRN
   MEX..IN STEP WITH PROGRESS OF CA CYCLONE.  SMALLER MID-UPPER LEVEL
   CIRCULATION IS EVIDENT IN MOISTURE CHANNEL IMAGERY OVER WRN ORE. 
   THIS FEATURE WILL WEAKEN...LOSING IDENTITY WITH TIME AS ITS
   VORTICITY FIELD IS ENTRAINED INTO TRAILING PORTION OF CA
   PERTURBATION.  WEAK SHORTWAVE TROUGH IS EVIDENT IN SATELLITE IMAGERY
   AND VWP/PROFILER DATA OVER SRN HIGH PLAINS ATTM...AND IS FCST TO
   DEAMPLIFY AS IT EJECTS NEWD OVER MO/AR THIS EVENING.
   
   AT SFC...15Z CHART SHOWED CYCLONE OVER SRN PORTION KS/CO BORDER
   REGION...WITH SYNOPTIC WARM FRONT ENEWD ACROSS N-CENTRAL/NERN KS AND
   WELL-DEFINED LEE TROUGH SSWWD OVER ERN NM.  DRYLINE SHOULD BECOME
   BETTER DEFINED TODAY FROM BIG-BEND REGION GENERALLY NNEWD ACROSS WRN
   TX/OK PANHANDLES...RETREATING WWD SOMEWHAT OVERNIGHT. SECONDARY SFC
   LOW...INITIALLY MORE CLOSELY RELATED TO MID-UPPER CYCLONE -- WAS
   EVIDENT OVER SRN NV IN DRA-LAS AREA...WITH PAC COLD FRONT ARCHING
   GENERALLY SWD OVER NRN BAJA.  INTERMOUNTAIN LOW AND LEE LOW SHOULD
   BEGIN TO MERGE OVER ERN CO AROUND END OF PERIOD.  BY THAT TIME...PAC
   COLD FRONT SHOULD CATCH UP TO RETREATED DRYLINE OVER PORTIONS TX
   PANHANDLE/SOUTH-PLAINS AND PERMIAN BASIN REGIONS.
   
   ...CENTRAL/SRN HIGH PLAINS...
   ISOLATED TSTMS ARE POSSIBLE BEFORE DARK NEAR DRYLINE...BUT
   POTENTIALLY SUPERCELLULAR IN CHARACTER.  SCATTERED TSTMS SHOULD FORM
   AFTER DARK...INCREASING IN COVERAGE THROUGH MUCH OF OVERNIGHT HOURS
   AS PAC COLD FRONT AND LARGE-SCALE ASCENT ALOFT CATCH UP TO DRYLINE. 
   GREATEST UNCONDITIONAL SVR THREAT IS OVER SRN HIGH PLAINS...BUT
   ISOLATED SVR DEVELOPMENT IS POSSIBLE AS FAR N AS ERN CO/WRN KS INVOF
   SFC LOW AND NEAR WARM FRONT.
   
   AS LEADING/WEAK SHORTWAVE TROUGH EJECTS AWAY FROM REGION...
   1. SUBTLE SHORTWAVE RIDGING WILL OCCUR...ACTING TO TEMPORARILY
   REINFORCE ELEVATED MIXED LAYER THROUGH WEAK DAVA/DVM WHILE EWD
   ADVECTION OF REMAINING EML CONTINUES.
   2. ASSOCIATED CLOUD COVER WILL MOVE AWAY...LEAVING BROAD GAP OF
   RELATIVELY CLEAR SKIES FOR REMAINDER DAYLIGHT HOURS PRIOR TO ARRIVAL
   OF NEXT UVV PLUME...NOW EVIDENT IN VIS/IR IMAGERY OVER AZ.
   3. DRYLINE WILL SHARPEN FROM COMBINATION OF MOIST ADVECTION FARTHER
   E AND STRENGTHENING MIXING ALONG AND W OF BOUNDARY.  W TX MESONET
   DATA INDICATES LOW-50S F SFC DEW POINTS HAVE REACHED AREA BETWEEN
   CDS-LBB.  THOUGH MOISTENING VIA ADVECTION WILL BE OFFSET SOMEWHAT BY
   HEATING/MIXING...EXPECT MID-UPPER 50S DEW POINTS IN NARROW CORRIDOR
   E OF DRYLINE BY 00Z...FROM ERN PANHANDLES/WRN OK SWD.
   
   MODIFIED RAOBS AND FCST SOUNDINGS SUGGEST 500-1000 J/KG MLCAPE
   POSSIBLE E OF CAPROCK OVER SRN PLAINS...SOMEWHAT LESS OVER HIGHER
   TERRAIN NEARER TO DRYLINE.  BUOYANCY ALSO SHOULD WEAKEN NWD OVER WRN
   KS WHERE MOISTURE WILL BE LESS.  ROBUST MID-UPPER LIFT IS NOT FCST
   TO REACH OUTLOOK AREA UNTIL OVERNIGHT -- LIKELY AFTER 03Z.  AS
   SUCH...EML-RELATED CAPPING SHOULD REMAIN STG...DELAYING ONSET OF
   SUBSTANTIAL CONVECTION WHILE LIMITING BOTH ITS SWD EXTENT AND
   DIURNAL COVERAGE.  STILL...A FEW TSTMS MAY DEVELOP BEFORE DARK INVOF
   DRYLINE...IN ENVIRONMENT CHARACTERIZED BY STRENGTHENING DEEP-LAYER
   AND AT LEAST ADEQUATE LOW-LEVEL SHEAR FOR SUPERCELLS.  EXPECT RISK
   OF DAMAGING GUSTS AND HAIL WITH ANY SUCH TSTMS...SUPPORTED BY
   INITIALLY HIGH LCL AND DEEP SUBCLOUD LAYER.
   
   LOW-LEVEL MOISTURE...DEEP SHEAR AND LOW-LEVEL SHEAR EACH SHOULD
   STRENGTHEN FROM LATE AFTN THROUGH EVENING AS MOIST ADVECTION
   CONTINUES E OF DRYLINE...TROUGH ALOFT APCHS...AND BROAD/45-55 KT LLJ
   TAKES SHAPE FROM W TX TO SERN NEB.  RELATED HODOGRAPH ENLARGEMENT
   SHOULD YIELD 250-450 J/KG EFFECTIVE SRH IN SUPPORT OF STORM-SCALE
   ROTATION.  DAMAGING GUSTS ARE POSSIBLE...THREAT DIMINISHING AFTER
   ABOUT 06Z...WITH INCREASING HAIL RISK INTO EVENING.  TORNADO
   POTENTIAL...WHILE NON-ZERO...IS MITIGATED BY LACK OF ROBUST
   MOISTURE...AND BY LIMITED TEMPORAL WINDOW BETWEEN EVENING LOWERING
   OF LCL AND LOSS OF SFC-BASED EFFECTIVE INFLOW.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: March 08, 2013
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