Apr 15, 2013 2000 UTC Day 1 Convective Outlook
Updated: Mon Apr 15 19:58:35 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20130415 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130415 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20130415 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20130415 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 100,231 12,944,858 Dallas, TX...Ft. Worth, TX...Tulsa, OK...Arlington, TX...St. Louis, MO...
   SPC AC 151955
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0255 PM CDT MON APR 15 2013
   
   VALID 152000Z - 161200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID-MS VALLEY TO THE
   SRN PLAINS...
   
   ...S-CNTRL PLAINS...OZARK PLATEAU...MID-MS VALLEY...
   PREVIOUS FORECAST REASONING REMAINS ON TRACK BUT MINOR ADJUSTMENTS
   HAVE BEEN MADE BASED PRIMARILY ON RECENT OBSERVATIONS/CONVECTION-
   ALLOWING MODEL GUIDANCE. FOR NEAR-TERM FORECAST INFORMATION PLEASE
   SEE MCD 0478. CU CONTINUE TO DEEPEN ALONG A QUASI-STATIONARY FRONT
   AND DRYLINE FROM NERN OK INTO N-CNTRL TX. ISOLATED TO SCATTERED
   TSTMS SHOULD FORM ALONG THESE BOUNDARIES IN THE NEXT FEW HOURS.
   CONVECTION-ALLOWING WRF GUIDANCE SUGGESTS THAT A COUPLE OF SUPERCELL
   CLUSTERS WILL EVENTUALLY EVOLVE E/NEWD. AS SUCH...HAVE SHIFTED
   ENHANCED SEVERE HAIL PROBABILITIES SWWD AND INCREASED TORNADO
   PROBABILITIES. OTHERWISE...AGREE WITH PREVIOUS DISCUSSION THAT
   GREATER TSTM COVERAGE WILL OCCUR LATER TONIGHT WITHIN A LOW-LEVEL
   WAA REGIME IN THE OZARK PLATEAU TO MID-MS VALLEY WITH A CONTINUING
   RISK FOR LARGE HAIL.
   
   ...S FL..
   MARGINAL SEVERE RISK SHOULD PERSIST NEXT FEW HOURS WITH NO MAJOR
   CHANGES NECESSARY.
   
   ..GRAMS.. 04/15/2013
   
   .PREV DISCUSSION... /ISSUED 1125 AM CDT MON APR 15 2013/
   
   ...SYNOPSIS...
   MODERATE TO STRONG MID-LATITUDE WESTERLIES CURRENTLY CURVE IN A
   BROAD CYCLONIC BELT ACROSS THE PACIFIC COAST THROUGH THE MID/UPPER
   MISSISSIPPI VALLEY AND GREAT LAKES REGION.  WITHIN THIS REGIME...AN
   EMBEDDED CLOSED LOW OVER THE UPPER MISSISSIPPI VALLEY IS FORECAST TO
   SHIFT NORTHEASTWARD INTO ONTARIO DURING THIS PERIOD...IN RESPONSE TO
   A VIGOROUS SHORT WAVE IMPULSE PIVOTING AROUND ITS NORTHEASTERN
   PERIPHERY.  AT THE SAME TIME...A VIGOROUS UPSTREAM SHORT WAVE TROUGH
   APPEARS LIKELY TO CONTINUE TO GRADUALLY DIG ACROSS THE PACIFIC COAST
   AND INTERMOUNTAIN REGION.  AS THIS OCCURS...MODELS SUGGEST SHARP
   UPPER RIDGING WILL BUILD ALONG THE ATLANTIC SEABOARD...IN THE WAKE
   OF LOW AMPLITUDE TROUGHING NOW SHIFTING EAST OF THE ATLANTIC COAST. 
   GENERAL MID-LEVEL HEIGHT RISES ARE ALSO EXPECTED ACROSS MUCH OF THE
   PLAINS AND MISSISSIPPI VALLEY REGION...THOUGH THIS COULD BE SLOWED
   OR SUPPRESSED BY A COUPLE OF SUBTLE IMPULSES EMBEDDED NOW
   PROGRESSING EAST OF THE ROCKIES AND NORTHERN MEXICAN PLATEAU REGION.
   
   WHILE MID-LEVEL HEIGHTS TEND TO RISE...A DEEPER SURFACE BASED COLD
   INTRUSION MAY CONTINUE TO NOSE SOUTHWARD THROUGH AT LEAST THE HIGH
   PLAINS.  THE COOL AIR WILL REMAIN SHALLOWER ACROSS THE LOWER PLAINS
   INTO THE MISSISSIPPI VALLEY...BUT THE LEADING EDGE COULD STILL
   ADVANCE SOUTHWARD A BIT ACROSS THE MIDDLE MISSISSIPPI VALLEY/OZARK
   PLATEAU AND ADJACENT SOUTH CENTRAL PLAINS.  A RETURN FLOW OF
   MOISTURE WILL CONTINUE...HOWEVER...OFF THE WESTERN GULF OF
   MEXICO...INTO AND ABOVE AT LEAST THE SHALLOWER PORTION OF THE
   SURFACE FRONT.  BENEATH STEEP MID-LEVEL LAPSE RATES...THIS PROBABLY
   WILL CONTRIBUTE TO A CORRIDOR OF SIZABLE CAPE...BOTH BOUNDARY LAYER
   BASED...SOUTH OF THE FRONT DURING THE LATE AFTERNOON AND EARLY
   EVENING...AND BASED WITHIN THE MOIST LAYER ABOVE THE FRONTAL
   INVERSION TO THE NORTH OF THE SURFACE FRONT.
   
   ...S CNTRL PLAINS/OZARK PLATEAU/MIDDLE MISSISSIPPI VALLEY...
   MODEL VARIABILITY CONCERNING FRONTAL PLACEMENT AND MID-LEVEL HEIGHT
   RISES ACROSS THE REGION ARE AT LEAST A COUPLE OF FACTORS
   CONTRIBUTING TO UNCERTAINTY WITH REGARD TO SEVERE PROBABILITIES FOR
   THIS FORECAST PERIOD.  THE DEGREE OF PRE-FRONTAL BOUNDARY LAYER
   MOISTENING MAY BE ANOTHER.  REGARDLESS...LARGE-SCALE FORCING FOR
   CONVECTIVE DEVELOPMENT APPEARS LIKELY TO REMAIN SUBTLE...AT
   BEST...AND THE LOCATION/EXTENT OF ANY BOUNDARY LAYER STORM
   DEVELOPMENT PRIOR TO THE ONSET OF SURFACE COOLING REMAINS UNCLEAR.  
   
   IT SEEMS POSSIBLE THAT FORCING FOR UPWARD VERTICAL
   MOTION...ASSOCIATED WITH A WEAK IMPULSE NOW MIGRATING NORTHEASTWARD
   ACROSS THE SOUTHERN HIGH PLAINS...COULD CONTRIBUTE TO LATE AFTERNOON
   STORM DEVELOPMENT AS FAR SOUTH AS NORTH CENTRAL TEXAS...NEAR THE
   INTERSECTION OF THE COLD FRONT AND A SHARPENING DRYLINE.  LATEST
   WATER VAPOR IMAGERY...AND OTHER OBSERVATIONAL DATA...STILL SUGGEST
   THAT A WINDOW OF OPPORTUNITY MAY EXIST FOR ISOLATED BOUNDARY LAYER
   BASED STORM DEVELOPMENT ACROSS PARTS OF NORTHERN ARKANSAS AND
   SOUTHERN MISSOURI.  IF STORMS DO INDEED FORM...DEEP LAYER SHEAR WILL
   BE SUFFICIENT FOR SUPERCELLS...CAPABLE OF AT LEAST PRODUCING LARGE
   HAIL AND LOCALLY DAMAGING WIND GUSTS.  AN ISOLATED TORNADO MAY ALSO
   NOT BE OUT OF THE QUESTION.  
   
   MODELS APPEAR TO SUGGEST BETTER POTENTIAL FOR MORE WIDESPREAD
   THUNDERSTORM ACTIVITY LATER THIS EVENING/OVERNIGHT...WITHIN A ZONE
   OF STRENGTHENING LOWER/MID TROPOSPHERIC WARM ADVECTION TO THE NORTH
   OF THE SURFACE FRONT.  THE RISK FOR LARGE HAIL WILL PROBABLY BE THE
   PRIMARY SEVERE THREAT WITH THIS ACTIVITY...ACROSS PARTS OF NORTHEAST
   OKLAHOMA/NORTHWEST ARKANSAS AND SOUTHERN MISSOURI.
   
   ...FLORIDA...
   LOWER/MID TROPOSPHERIC DRYING...AND WARMING ALOFT...ARE CONTRIBUTING
   TO UNCERTAIN CONVECTIVE POTENTIAL TO THE NORTH OF A WEAKENING
   SURFACE BOUNDARY NOW CURVING ACROSS SOUTHEAST COASTAL AREAS AND THE
   KEYS.  BUT REMNANT MID-LEVEL TROUGHING NOW PROGRESSING ACROSS THE
   FLORIDA PENINSULA COULD STILL CONTRIBUTE TO STORM FORMATION ALONG
   DEVELOPING SEA BREEZES FARTHER TO THE NORTH ACROSS THE SOUTHERN
   PENINSULA THIS AFTERNOON.  AND SHEAR BENEATH THE LINGERING
   SUBTROPICAL JET MAY ENHANCE ACTIVITY...SUPPORTING LOW PROBABILITIES
   FOR A SEVERE WIND GUST OR TWO...PERHAPS SOME HAIL.
   
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