Apr 18, 2015 2000 UTC Day 1 Convective Outlook
Updated: Sat Apr 18 19:49:00 UTC 2015 (20150418 2000Z Day 1 shapefile | 20150418 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150418 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 96,181 6,430,996 San Antonio, TX...Oklahoma City, OK...Laredo, TX...Killeen, TX...Norman, OK...
SLIGHT 150,678 11,987,228 Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...Wichita, KS...
MARGINAL 369,246 28,892,840 Houston, TX...Kansas City, MO...New Orleans, LA...Omaha, NE...Tulsa, OK...
Probabilistic Tornado Graphic
20150418 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.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 89,226 1,031,577 Wichita Falls, TX...Grand Island, NE...Kearney, NE...Dodge City, KS...North Platte, NE...
2 % 359,425 36,065,418 Houston, TX...San Antonio, TX...Dallas, TX...Austin, TX...Fort Worth, TX...
Probabilistic Damaging Wind Graphic
20150418 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.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 237,288 18,389,647 San Antonio, TX...Dallas, TX...Austin, TX...Fort Worth, TX...Oklahoma City, OK...
5 % 370,502 28,848,477 Houston, TX...Kansas City, MO...New Orleans, LA...Omaha, NE...Tulsa, OK...
Probabilistic Large Hail Graphic
20150418 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.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
30 % 96,285 6,443,235 San Antonio, TX...Oklahoma City, OK...Laredo, TX...Killeen, TX...Norman, OK...
15 % 150,929 11,982,942 Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...Wichita, KS...
5 % 368,892 28,884,886 Houston, TX...Kansas City, MO...New Orleans, LA...Omaha, NE...Tulsa, OK...
   SPC AC 181949

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0249 PM CDT SAT APR 18 2015

   VALID 182000Z - 191200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM PARTS OF WRN AND CENTRAL
   KS SWD ACROSS CENTRAL TX TO THE RIO GRANDE...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM NERN CO/SRN NEB SWD ACROSS
   CENTRAL AND S TX...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   AREA...AND ALSO EXTENDING EWD ACROSS THE GULF COAST STATES...

   ...SUMMARY...
   SCATTERED THUNDERSTORMS WILL CONTINUE THIS AFTERNOON AND EVENING
   FROM THE CENTRAL PLAINS TO SOUTH TEXAS...SOME OF WHICH WILL PRODUCE
   HAIL AND SEVERE WIND GUSTS.  A FEW TORNADOES CANNOT BE RULED
   OUT...PARTICULARLY ACROSS THE NORTHERN HALF OF THIS AREA.

   ...DISCUSSION...
   GENERAL FORECAST REASONING AND AREAS REMAIN VALID THIS UPDATE...WITH
   THE MAJOR ADJUSTMENT BEING MADE ATTM TO EXTEND HIGHER /5%/ TORNADO
   PROBABILITY SWD ACROSS THE WRN OK VICINITY.  HERE...LOW-LEVEL FLOW
   CONTINUES TO BACK AHEAD OF THE SURFACE DRYLINE...RESULTING IN SOME
   ENHANCEMENT TO THE LOW-LEVEL SHEAR AS COMPARED TO EARLIER IN THE
   DAY.  AS SUCH...RISK FOR TORNADOES HAS LIKELY BECOME SLIGHTLY
   ENHANCED OVER THIS AREA.  ELSEWHERE...STORMS CONTINUE TO INCREASE
   FROM ERN CO/WRN KS SWD ACROSS WRN OK TO THE TX BIG BEND
   REGION...ALONG THE PRIMARY AXIS OF FORECAST SEVERE RISK.

   ..GOSS.. 04/18/2015

   .PREV DISCUSSION... /ISSUED 1123 AM CDT SAT APR 18 2015/

   ..CENTRAL/SOUTHERN PLAINS...
   MORNING WATER VAPOR LOOPS SHOW A PERSISTENT UPPER LOW OVER CO...WITH
   SEVERAL SHORTWAVE TROUGHS ROTATING THROUGH THE BASE OF THE LOW INTO
   THE SOUTHERN PLAINS.  ONE SUCH FEATURE IS EVIDENT OVER SOUTHEAST
   NM...WHICH WILL TRACK INTO WEST TX AND EVENTUALLY INTO WESTERN OK
   LATER TODAY/TONIGHT.  VISIBLE SATELLITE IMAGERY SHOWS POCKETS OF LOW
   CLOUDS ALONG THE DRYLINE FROM WESTERN KS INTO WEST-CENTRAL TX...BUT
   THOSE CLOUDS WILL LIKELY ERODE BY EARLY AFTERNOON ALLOWING STRONG
   HEATING TO TAKE PLACE.  DEWPOINTS IN THE 60S AND COOL TEMPERATURES
   ALOFT /-16 AND COLDER AT 500MB/ WILL HELP CONTRIBUTE TO AFTERNOON
   MLCAPE VALUES OF 1500+ J/KG AND ONLY A WEAK CAP.  

   SCATTERED THUNDERSTORMS ARE EXPECTED TO FORM ALONG THE ENTIRE LENGTH
   OF THE DRYLINE FROM WESTERN KS INTO WEST TX. SUFFICIENT DEEP-LAYER
   EFFECTIVE SHEAR WILL SUPPORT SUPERCELL STORM STRUCTURES CAPABLE OF
   LARGE HAIL AND PERHAPS DAMAGING WINDS.  ISOLATED TORNADOES ARE ALSO
   POSSIBLE...BUT WEAK LOW LEVEL VERTICAL SHEAR WILL BE A LIMITING
   FACTOR.  THE AREA OF PERHAPS GREATEST TORNADO THREAT WOULD BE OVER
   WESTERN KS INTO WESTERN NEB WHERE EASTERLY NEAR-SURFACE WINDS WILL
   ENHANCE SHEAR.  STORMS THROUGHOUT THE RISK AREA SHOULD PERSIST INTO
   MID-EVENING BEFORE SLOWLY WEAKENING.

   ...GULF COAST STATES...
   A LARGE MCS REMAINS OFF THE COAST OF LA/MS TODAY...LIMITING INFLOW
   INLAND AND MAINTAINING WIDESPREAD CLOUD COVER OVER THE GULF COAST
   STATES.  SLOW/PARTIAL CLEARING IS EXPECTED THROUGH THE AFTERNOON
   OVER PARTS OF LA/MS...WHERE DEWPOINTS ARE IN THE UPPER 60S.  THIS
   MAY LEAD TO POCKETS OF MLCAPE OF 1000 J/KG.  FORECAST SOUNDINGS IN
   THIS REGION ARE MOIST WITH RATHER WEAK MID LEVEL LAPSE RATES AND
   DISORGANIZED LOW LEVEL WINDS.  FOR THIS REASON...WILL MAINTAIN ONLY
   MARGINAL SEVERE PROBABILITIES ACROSS THE REGION.  IF STRONGER
   DESTABILIZATION CAN OCCUR THAN CURRENTLY ANTICIPATED...PORTIONS OF
   THE AREA MAY NEED TO BE UPGRADED TO SLIGHT RISK.

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