Apr 9, 2015 1630 UTC Day 1 Convective Outlook
Updated: Thu Apr 9 16:30:27 UTC 2015 (20150409 1630Z Day 1 shapefile | 20150409 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150409 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 221,994 30,010,184 Chicago, IL...Indianapolis, IN...Memphis, TN...St. Louis, MO...Louisville, KY...
SLIGHT 231,932 38,670,989 Dallas, TX...Detroit, MI...Columbus, OH...Fort Worth, TX...Milwaukee, WI...
MARGINAL 246,727 30,228,949 San Antonio, TX...Austin, TX...Charlotte, NC...Raleigh, NC...Pittsburgh, PA...
Probabilistic Tornado Graphic
20150409 1630 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
SIG SEVERE 35,873 8,815,053 Aurora, IL...Rockford, IL...Naperville, IL...Joliet, IL...Springfield, IL...
10 % 42,725 11,856,122 Chicago, IL...Aurora, IL...Rockford, IL...Naperville, IL...Joliet, IL...
5 % 190,534 21,779,559 Indianapolis, IN...Memphis, TN...Milwaukee, WI...St. Louis, MO...Louisville, KY...
2 % 242,219 32,949,225 Dallas, TX...Detroit, MI...Columbus, OH...Nashville, TN...Cleveland, OH...
Probabilistic Damaging Wind Graphic
20150409 1630 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
30 % 181,375 27,378,851 Chicago, IL...Indianapolis, IN...Memphis, TN...St. Louis, MO...Louisville, KY...
15 % 254,601 39,851,114 Dallas, TX...Detroit, MI...Columbus, OH...Fort Worth, TX...Milwaukee, WI...
5 % 247,040 30,515,359 San Antonio, TX...Austin, TX...Charlotte, NC...Raleigh, NC...Pittsburgh, PA...
Probabilistic Large Hail Graphic
20150409 1630 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 % 96,685 6,088,421 Shreveport, LA...Little Rock, AR...Springfield, IL...Peoria, IL...Davenport, IA...
15 % 237,735 42,408,321 Chicago, IL...Dallas, TX...Indianapolis, IN...Memphis, TN...Fort Worth, TX...
5 % 349,235 46,954,068 San Antonio, TX...Detroit, MI...Columbus, OH...Austin, TX...Charlotte, NC...
   SPC AC 091630

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1130 AM CDT THU APR 09 2015

   VALID 091630Z - 101200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM THE ARKLATEX NORTHEAST
   INTO THE SRN GRT LKS/LWR OH VLY...

   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENHD AREA FROM
   E TX INTO THE UPR OH VLY...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE ABOVE AREAS
   FROM S CNTRL TX TO THE CNTRL APPALACHIANS...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE LIKELY TODAY INTO TONIGHT OVER A BROAD
   SWATH FROM PARTS OF TEXAS NORTHEASTWARD THROUGH THE LOWER AND
   MID-MISSISSIPPI VALLEYS INTO THE OHIO VALLEY AND SOUTHERN GREAT
   LAKES. THESE WILL PRODUCE DAMAGING WIND...HAIL...AND A FEW
   TORNADOES...ONE OR TWO OF WHICH COULD BE STRONG.

   ...SYNOPTIC SETUP...
   PROGRESSIVE...MULTI-STREAM FLOW WILL PREVAIL OVER THE CNTRL AND ERN
   U.S. THIS PERIOD...DOWNSTREAM FROM WRN STATES SPLIT. STRONG
   SHORTWAVE TROUGH NOW EXITING THE CNTRL HIGH PLNS SHOULD ACCELERATE
   ENE INTO ERN IA THIS EVE...BEFORE FURTHER ACCELERATING AND TURNING
   NE TO NEAR SSM EARLY FRI AS NRN BRANCH IMPULSE AMPLIFIES SE INTO MN.
   AT THE SAME TIME...WEAKER LEAD DISTURBANCE NOW CROSSING THE OZARKS
   SHOULD MOVE NE INTO THE MID-OH VLY BY THIS EVE...AND INTO NY/PA
   EARLY FRI...AS DEEP SWLY FLOW STRENGTHENS ACROSS THE E-CNTRL AND ERN
   U.S.

   AT THE SFC...NW MO LOW EXPECTED TO DEEPEN NEWD INTO SRN WI BY THIS
   EVE...AND UNDERGO FURTHER DEEPENING AS IT REACHES THE SSM AREA EARLY
   FRI. COLD FRONT TRAILING SSW FROM THE LOW SHOULD STRENGTHEN AND
   ACCELERATE E ACROSS THE MID-MISSISSIPPI VALLEY AND OZARKS BY LATE
   TODAY...AND INTO THE UPR OH...TN...AND LWR MS VLYS EARLY FRI...WHILE
   MORE DIFFUSE WARM FRONT ADVANCES N INTO LWR MI.

   IN SUMMARY...THE OVERALL SET-UP SUPPORTS A BROAD AREA WITH AN
   APPRECIABLE RISK FOR SVR WEATHER LATER TODAY THROUGH EARLY FRI...BUT
   WITH MITIGATING FACTORS THAT LIKELY WILL KEEP THE CORRIDORS OF
   GREATEST RISK SOMEWHAT FRAGMENTED AND MULTI-MODAL.

   ...MID-MS VLY TO SRN GRT LKS THIS AFTN THROUGH EARLY TNGT...
   SEVERAL FACTORS MAY COMBINE TO YIELD A MESOSCALE CORRIDOR OF
   SOMEWHAT ENHANCED SVR THREAT...INCLUDING THE POTENTIAL FOR A COUPLE
   STRONG TORNADOES...OVER THE ERN IA/NE MO/NRN IL/SRN WI AREA LATER
   TODAY INTO EARLY TNGT. PERSISTENT HEIGHT FALLS ACROSS
   REGION...LARGELY DUE TO AMPLIFICATION OF UPSTREAM...LARGER-SCALE
   TROUGH...WILL OFFSET SINKING/DESCENT OCCURRING IN WAKE OF LEAD UPR
   IMPULSE AND EMBEDDED MCV NOW CROSSING THE OZARKS. AT THE SAME
   TIME...SATELLITE SUGGESTS LIKELIHOOD FOR AT LEAST MODEST SFC HEATING
   AHEAD OF COLD FRONT AND DEEPENING SFC LOW APPROACHING FROM NW MO.

   WITH 700 MB SWLY WINDS INCREASING TO AOA 60 KTS ATOP 40+ KT SSW FLOW
   AT 850 MB...HODOGRAPHS WILL BE FAVORABLE FOR SUSTAINED SUPERCELLS
   WITH LARGE HAIL. THE DIRECTIONAL COMPONENT TO LOW-LVL SHEAR LIKELY
   WILL NOT BE GREAT. BUT COMBINATION OF STRENGTHENING FLOW AND
   EXPECTED BACKING OF NEAR-SFC WINDS/ENHANCED SRH IMMEDIATELY AHEAD OF
   SFC LOW SUGGEST THAT A CORRIDOR OF HEIGHTENED TORNADO POTENTIAL
   COULD EVOLVE LATER THIS AFTN...BEFORE THE STORMS MERGE INTO BROKEN
   LINES/SMALL CLUSTERS EARLY TNGT. ALTHOUGH CLOUDS AND SHOWERS MAY
   DELAY NWD ADVANCE OF WARM FRONT ACROSS IL/IND...STRENGTHENING SFC
   PRESSURE FALLS/TRACK OF SFC LOW FURTHER INDICATE THAT THE SVR THREAT
   COULD EXTEND NWD INTO SRN WI AND SW LWR MI...WITH DMGG WINDS
   BECOMING THE DOMINANT THREAT OVER TIME.

   ...LWR OH VLY SW INTO E TX/LWR MS VLY LATE TODAY THROUGH EARLY
   FRI...

   SFC HEATING AND UPLIFT ALONG COLD FRONT AND PRE-FRONTAL CONFLUENCE
   AXES EXPECTED TO INITIATE TSTMS LATER TODAY THROUGH TNGT AS EML CAP
   IS BROKEN. ALTHOUGH WIND FIELDS WILL BE WEAKER RELATIVE TO POINTS
   N...AMPLE /40+ KT/ WSWLY DEEP SHEAR WILL EXIST FOR SUSTAINED
   STORMS/SUPERCELLS...ESPECIALLY OVER THE LWR OH AND TN VLYS. GIVEN
   FAIRLY RICH MOISTURE AVAILABILITY /PW AOA 1.50 INCHES/...IN THEIR
   EARLY STAGES THESE STORMS COULD YIELD LARGE HAIL AND A FEW
   TORNADOES. WITH TIME...DEGREE OF LOW-LVL FORCING SHOULD RESULT INTO
   AMALGAMATION OF CONVECTION INTO AN EXTENSIVE...BROKEN SQLN. EMBEDDED
   LEWPS AND BOWING STRUCTURES LIKELY WILL BE ACCOMPANIED BY A SLOWLY
   DIMINISHING RISK FOR DMGG WIND INTO EARLY FRI.

   ...UPR OH LY/CNTRL APPALACHIANS THIS AFTN/EVE...
   A CONDITIONAL RISK WILL EXIST FOR LOOSELY-ORGANIZED CLUSTERS OF
   MAINLY MULTICELL STORMS WITH HAIL AND LOCALLY DMGG WIND THIS AFTN
   OVER PARTS OF OH...KY AND WRN SLOPES OF THE CNTRL
   APPALACHIANS...WHERE SFC HEATING WILL FURTHER DESTABILIZE REGION OF
   MODEST LOW-LVL MOISTURE AND MID-LVL INSTABILITY. SOME OF THIS
   ACTIVITY COULD ARISE FROM EXISTING AREAS OF ELEVATED CONVECTION NOW
   OVER PARTS OF THE REGION...WITH OTHER STORMS INITIATED BY
   DIFFERENTIAL HEATING ALONG RESIDUAL SFC BOUNDARIES. MOST OF THE
   STORMS SHOULD WEAKEN WITH NIGHTFALL...ALTHOUGH PARTS OF THE OH VLY
   COULD EXPERIENCE A SECOND ROUND OF STORMS LATE TNGT AS MID MS VLY
   COLD FRONT APPROACHES REGION.

   ..CORFIDI/GRAMS/MOSIER.. 04/09/2015

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