Aug 11, 2010 2000 UTC Day 1 Convective Outlook
Updated: Wed Aug 11 19:55:47 UTC 2010
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20100811 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20100811 2000 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20100811 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20100811 2000 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 111952
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0252 PM CDT WED AUG 11 2010
   
   VALID 112000Z - 121200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS TONIGHT ACROSS PARTS OF THE NRN
   PLAINS...
   
   ...20Z UPDATE...
   SLIGHT RISK PROBABILITIES HAVE BEEN ADDED TO PARTS OF THE NORTHERN
   PLAINS.  NO CHANGES ELSEWHERE.
   
   ...NRN PLAINS...
   LATEST RUC GUIDANCE INDICATES THAT THE MOIST BOUNDARY LAYER...
   ALONG/NORTH OF A QUASI-STATIONARY SURFACE FRONT EXTENDING EAST OF A
   MONTANA SURFACE LOW THROUGH SOUTH CENTRAL NORTH DAKOTA...HAS
   DESTABILIZED WITH SURFACE HEATING.  MIXED LAYER CAPE IS MODERATELY
   LARGE...AROUND 200O J/KG...BUT INHIBITION FOR BOUNDARY LAYER PARCELS
   REMAINS CONSIDERABLE BENEATH A CAPPING ELEVATED MIXED LAYER.
   
   HOWEVER...MOST MODEL GUIDANCE CONTINUES TO INDICATE THAT LARGE-SCALE
   FORCING FOR UPWARD VERTICAL MOTION WILL INCREASE BY MID TO LATE
   EVENING...IN RESPONSE TO STRENGTHENING LOW-LEVEL WARM
   ADVECTION...AND STRENGTHENING HIGH-LEVEL DIVERGENCE IN THE EXIT
   REGION OF AN UPPER JET EMERGING FROM THE GREAT BASIN.  THIS SHOULD
   CONTRIBUTE TO CONVECTIVE DEVELOPMENT...AND POTENTIAL EXISTS FOR
   STORM CONSOLIDATION AND UPSCALE CONVECTIVE GROWTH INTO AN ORGANIZED
   MESOSCALE CONVECTIVE SYSTEM...PARTICULARLY NEAR THE NOSE OF A 30-40
   KT LOW-LEVEL JET ACROSS PARTS OF WESTERN INTO CENTRAL NORTH DAKOTA. 
   
   
   IF THIS OCCURS...THERMODYNAMIC PROFILES CHARACTERIZED BY STEEP
   MID-LEVEL LAPSE RATES AND SIZABLE LOWER/MID-LEVEL TEMPERATURE-DEW
   POINT SPREADS...ABOVE THE SHALLOW FRONTAL INVERSION...WILL BE
   CONDUCIVE TO DOWNBURSTS...AND SURFACE COLD POOL DEVELOPMENT.  AS THE
   DOWNWARD TRANSFER OF MOMENTUM ASSOCIATED WITH MODEST WESTERLY
   MID-LEVEL FLOW CONTRIBUTES TO AN EAST/SOUTHEASTWARD MOTION OF THE
   COLD POOL...AN EASTERLY COMPONENT TO THE BOUNDARY LAYER FLOW WILL
   ENHANCE THE POTENTIAL FOR STRONG SURFACE GUSTS.
   
   ..KERR.. 08/11/2010
   
   .PREV DISCUSSION... /ISSUED 1105 AM CDT WED AUG 11 2010/
   
   ...NORTHERN HIGH PLAINS TO NRN ROCKIES...
   UPPER LOW ERN OR WILL BEGIN TO DRIFT EWD INTO SWRN ID TONIGHT. 
   STRONGER SWLY FLOW AHEAD OF LOW WILL SPREAD EWD ACROSS MT/NRN WY
   INTO THE NRN HIGH PLAINS TODAY AND TONIGHT.  WITH LITTLE IN THE WAY
   OF UPPER FORCING...STILL EXPECT THE SEVERE THREAT WITH THE SCATTERED
   DIURNAL THUNDERSTORMS TO BE INSUFFICIENT TO JUSTIFY INTRODUCING A
   SEVERE RISK ATTM.  STRONG HEATING AND STEEP LAPSE RATES COUPLED WITH
   SBCAPES TO 1000 J/KG WILL LEAD TO POTENTIAL FOR GUSTY WINDS AND
   ISOLATED SEVERE WIND DAMAGE ALONG WITH MARGINAL HAIL DEVELOPING
   INITIALLY OVER HIGHER TERRAIN CENTRAL ID/WRN MT SPREADING EWD ACROSS
   HIGH PLAINS BY THIS EVENING.
   
   AS SOUTHERLY LOW LEVEL WINDS STRENGTHEN ACROSS THE NRN HIGH PLAINS E
   OF LEE SURFACE TROUGH...SHEAR WILL INCREASE OVERNIGHT AND THIS AREA
   WILL BE MONITORED FOR A POSSIBLE UPGRADE TO SLIGHT RISK IF
   SUFFICIENT INSTABILITY CAN DEVELOP.
   
   ...OH VALLEY...
   WEAK UPPER TROUGH TRACKING EWD ACROSS UPPER GREAT LAKES AS NOTED ON
   W/V IMAGERY.  THE MARGINALLY SEVERE STORMS THAT DEVELOPED THIS AM IN
   RESPONSE TO APPROACH OF TROUGH CURRENTLY MOVING ACROSS LOWER MI AND
   NRN OH VALLEY.
   
   WHILE VERTICAL SHEAR REMAINS QUITE WEAK AHEAD OF THESE
   STORMS...HEATING OF THE VERY MOIST AIRMASS ACROSS OH VALLEY WILL
   LEAD TO VERY UNSTABLE CONDITIONS WITH SBCAPES TO 4000 J/KG THIS
   AFTERNOON.  THERE WILL CONTINUE TO BE A MARGINAL WIND DAMAGE THREAT
   WITH STORMS DEVELOPING ALONG AND AHEAD OF THIS MORNINGS
   ACTIVITY...PARTICULARLY WHERE COLD POOLS CAN ORGANIZE AND ENHANCE
   DOWNBURST POTENTIAL. HOWEVER GIVEN THE LIMITED SHEAR...EXPECTED
   COVERAGE OF SEVERE STORMS SEEMS INSUFFICIENT FOR INTRODUCING A
   SLIGHT RISK.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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