Oct 17, 2007 0600 UTC Day 1 Convective Outlook
Updated: Wed Oct 17 09:26:18 UTC 2007
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the southern and central plains and ozarks today through thursday morning....   Please read the latest public statement about this event.

Categorical Graphic
20071017 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20071017 1200 UTC Day 1 Tornado Probabilities Graphic
Probabilistic Damaging Wind Graphic
20071017 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probabilistic Large Hail Graphic
20071017 1200 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 170552
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1252 AM CDT WED OCT 17 2007
   
   VALID 171200Z - 181200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT OVER
   SERN KS...PARTS OF CNTRL/ERN OK...AR AND SRN MO...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE CNTRL AND SRN
   PLAINS EWD INTO THE MID AND LOWER MS VALLEY...
   
   ...SYNOPSIS...
   
   SIGNIFICANT INTENSIFICATION OF CNTRL U.S. UPPER TROUGH IS FORECAST
   AS STRONG MID AND HIGH-LEVEL JET STREAKS PROPAGATE FROM THE SRN
   ROCKIES INTO THE SRN PLAINS AND EWD INTO THE LOWER/MID MS VALLEY. 
   EMBEDDED SHORT WAVE TROUGH OVER WRN NM AS OF 17/05Z WILL LIFT
   RAPIDLY NEWD INTO CNTRL/SRN PLAINS BY LATE THIS AFTERNOON OR
   EVENING...AND EVENTUALLY INTO THE MIDWEST BY THURSDAY MORNING.
   
   IN THE LOW LEVELS...PRIMARY SURFACE LOW WILL DEEPEN TODAY OVER SWRN
   KS BEFORE DEVELOPING RAPIDLY NEWD INTO ERN NEB OR WRN IA BY THE END
   OF THE FORECAST PERIOD.  DRYLINE EXTENDING SWD FROM THIS LOW WILL
   MIX/ADVECT EWD INTO WRN OK AND NWRN TX BY MID TO LATE
   AFTERNOON...LIKELY PROVIDING THE FOCUS FOR SEVERE TSTM DEVELOPMENT
   LATER TODAY.  ELSEWHERE...WARM FRONT /EFFECTIVELY DELINEATING A
   NOTABLE INCREASE IN BOUNDARY LAYER MOISTURE/ WILL LIFT NWD THROUGH
   THE CNTRL PLAINS...MID MS VALLEY AND LOWER OH VALLEY THROUGH THE
   PERIOD.
   
   ...CNTRL/SRN PLAINS EWD INTO THE MID/LOWER MS VALLEY...
   
   --A POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE IS EXPECTED THIS
   AFTERNOON AND TONIGHT WITH A THREAT OF STRONG...LONG-TRACKED
   TORNADOES--
   
   17/00Z UPPER-AIR ANALYSES AND CURRENT GOES IPW DATA SHOW A RAPID
   RETURN OF RICHER BOUNDARY LAYER MOISTURE NWD THROUGH THE SRN PLAINS
   WITH A MARITIME TROPICAL AIR MASS /I.E. DEWPOINTS IN THE UPPER 60S
   TO LOWER 70S/ NOW IN PLACE FROM SRN TX EWD ACROSS THE CNTRL GULF
   COAST.  STRENGTHENING SLY LOW-LEVEL FLOW FROM THE SRN/CNTRL PLAINS
   EWD THROUGH THE MS RIVER VALLEY WILL ENHANCE THE TRANSPORT OF THIS
   MOISTURE NWD THROUGH THE CNTRL PART OF THE NATION TODAY AND TONIGHT.
   THIS INCREASE IN LOW-LEVEL MOISTURE COUPLED WITH STEEPENING
   MID-LEVEL LAPSE RATES IS EXPECTED TO CONTRIBUTE TO A MODERATELY
   UNSTABLE AIR MASS BY AFTERNOON E OF DRY LINE FROM CNTRL/ERN TX NWD
   THROUGH OK INTO KS WITH MLCAPES OF 1000-1500 J/KG.  FARTHER E OVER
   THE LOWER MS VALLEY/MID SOUTH...LAPSE RATES WILL BE WEAKER...THOUGH
   COMPARABLY RICHER BOUNDARY LAYER MOISTURE AND DAYTIME HEATING WILL
   SUPPORT MLCAPES OF 1000-1500 J/KG.
   
   TSTMS CURRENTLY DEVELOPING OVER THE TX PNHDL ARE EXPECTED TO BE IN
   PROGRESS AT THE ONSET OF THE FORECAST PERIOD OVER PARTS OF NWRN
   TX...OK AND KS IN ASSOCIATION WITH WEAKER...LEAD SHORT WAVE TROUGH
   EJECTING NEWD THROUGH THE SRN HIGH PLAINS.  THESE STORMS ARE
   EXPECTED TO INCREASE IN COVERAGE AND INTENSITY THROUGH THE DAY WHILE
   MOVING/DEVELOPING NEWD TOWARD THE LOWER MO VALLEY WITH THE POTENTIAL
   FOR EMBEDDED SUPERCELLS CAPABLE OF HAIL...DAMAGING WINDS AND PERHAPS
   A COUPLE TORNADOES.
   
   MORE SIGNIFICANT...SEVERE STORM DEVELOPMENT IS ANTICIPATED IN WAKE
   OF EARLIER STORM ACTIVITY LATER THIS AFTERNOON FROM VICINITY OF
   SURFACE LOW OVER SWRN KS SWD/SEWD ALONG DRY LINE INTO WRN/CNTRL OK
   AND FAR N-CNTRL TX.  THE COMBINATION OF MODERATE INSTABILITY AND
   MODERATE TO STRONG LOW AND DEEP-LAYER SHEAR SUGGEST A HIGH LIKLIHOOD
   OF SUPERCELLS CAPABLE OF LARGE HAIL...DAMAGING WINDS AND
   TORNADOES...A FEW OF WHICH COULD BE STRONG AND LONG-TRACKED.  THIS
   IS ESPECIALLY THE CASE FROM SERN KS AND ERN OK INTO AR AND SRN MO
   THIS EVENING AND TONIGHT WHERE DEEP-LAYER FORCING FOR ASCENT WILL BE
   CONCENTRATED IN ADVANCE OF PRIMARY SHORT WAVE TROUGH.
   
   ELSEWHERE...TSTMS WILL BECOME INCREASINGLY NUMEROUS TODAY OVER PARTS
   OF THE LOWER MS VALLEY INTO THE MID SOUTH WITHIN A VERY MOIST AND
   MODERATELY UNSTABLE AIR MASS RETURNING NWD.  FORECAST SOUNDINGS
   INDICATE VERTICAL SHEAR PROFILES QUITE SUPPORTIVE OF SUPERCELLS
   CAPABLE OF TORNADOES /SOME STRONG/ AND PERHAPS ISOLATED WIND AND/OR
   HAIL.  THIS REGIME WILL CONTINUE NWD OVERNIGHT ALONG ERN BRANCH OF
   LLJ THROUGH PORTIONS OF THE MID MS AND LOWER OH VALLEYS...LIKELY
   MERGING WITH OTHER STORM CLUSTERS ORIGINATING OVER THE CNTRL/SRN
   PLAINS IN ADVANCE OF ABOVE-MENTIONED SHORT WAVE TROUGH.  SUPERCELLS
   WILL REMAIN POSSIBLE OVERNIGHT WITH A THREAT OF TORNADOES...LOCALLY
   STRONG WIND GUSTS AND SOME HAIL.
   
   ..MEAD/GUYER.. 10/17/2007
   
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