Dec 23, 2015 1630 UTC Day 1 Convective Outlook
Updated: Wed Dec 23 16:34:12 UTC 2015 (20151223 1630Z Day 1 shapefile | 20151223 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...Severe thunderstorms expected over parts of the Mid South region today....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20151223 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 74,768 7,387,170 Memphis, TN...Nashville, TN...Louisville, KY...Evansville, IN...Clarksville, TN...
ENHANCED 107,140 11,593,870 Indianapolis, IN...Cincinnati, OH...Lexington-Fayette, KY...Little Rock, AR...Jackson, MS...
SLIGHT 297,196 48,943,291 Chicago, IL...Columbus, OH...Atlanta, GA...St. Louis, MO...Toledo, OH...
MARGINAL 268,854 35,025,608 Detroit, MI...Charlotte, NC...Milwaukee, WI...New Orleans, LA...Cleveland, OH...
Probabilistic Tornado Graphic
20151223 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 68,670 5,998,255 Memphis, TN...Nashville, TN...Clarksville, TN...Murfreesboro, TN...Jackson, TN...
15 % 72,940 6,449,632 Memphis, TN...Nashville, TN...Clarksville, TN...Murfreesboro, TN...Jackson, TN...
10 % 43,952 3,961,565 Louisville, KY...Little Rock, AR...Evansville, IN...North Little Rock, AR...Pine Bluff, AR...
5 % 276,376 35,332,215 Indianapolis, IN...Atlanta, GA...St. Louis, MO...Cincinnati, OH...Lexington-Fayette, KY...
2 % 218,534 38,539,032 Chicago, IL...Columbus, OH...Charlotte, NC...Milwaukee, WI...New Orleans, LA...
Probabilistic Damaging Wind Graphic
20151223 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
SIG SEVERE 34,475 4,592,440 Nashville, TN...Louisville, KY...Evansville, IN...Clarksville, TN...Murfreesboro, TN...
45 % 43,397 5,335,202 Nashville, TN...Louisville, KY...Evansville, IN...Clarksville, TN...Murfreesboro, TN...
30 % 138,413 13,637,206 Indianapolis, IN...Memphis, TN...Cincinnati, OH...Lexington-Fayette, KY...Little Rock, AR...
15 % 295,087 48,825,670 Chicago, IL...Columbus, OH...Atlanta, GA...St. Louis, MO...Toledo, OH...
5 % 269,244 34,980,379 Detroit, MI...Charlotte, NC...Milwaukee, WI...New Orleans, LA...Cleveland, OH...
Probabilistic Large Hail Graphic
20151223 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
15 % 110,564 8,995,695 Memphis, TN...St. Louis, MO...Jackson, MS...Springfield, IL...Peoria, IL...
5 % 230,982 22,378,610 Nashville, TN...New Orleans, LA...Louisville, KY...Birmingham, AL...Baton Rouge, LA...
   SPC AC 231634

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1034 AM CST WED DEC 23 2015

   VALID 231630Z - 241200Z

   ...THERE IS A MDT RISK OF SVR TSTMS OVER FAR SRN PORTIONS OF
   IL/IND...WRN AND CNTRL KY....SERN MO....ERN AR...WRN AND MIDDLE
   TN....NRN MS AND FAR NWRN AL...

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM THE OH TO LOWER MS
   VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN GREAT LAKES TO
   GULF COAST...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE GREAT LAKES TO GULF
   COAST AND SRN MID-ATLANTIC...

   ...SUMMARY...
   AN OUTBREAK OF SEVERE THUNDERSTORMS AND TORNADOES IS FORECAST TODAY
   INTO TONIGHT FROM THE OHIO VALLEY INTO THE TENNESSEE AND LOWER
   MISSISSIPPI VALLEYS.  THE GREATEST RISK FOR A FEW
   INTENSE...LONG-TRACKED TORNADOES WILL EXIST OVER WESTERN TENNESSEE
   INTO NORTHERN MISSISSIPPI AND EASTERN ARKANSAS THIS AFTERNOON INTO
   TONIGHT.

   ...SYNOPSIS...

   A NEGATIVELY TILTED MID-LEVEL TROUGH FROM THE CNTRL HIGH PLAINS TO
   ARKLATEX WILL EJECT NEWD THROUGH THE MID-MS VALLEY INTO UPPER GREAT
   LAKES AHEAD OF AN AMPLIFYING UPSTREAM SYSTEM ALONG THE PACIFIC NW
   COAST.  AT THE SURFACE...AN AREA OF LOW PRESSURE OVER NERN KS WILL
   CONCURRENTLY DEVELOP NEWD TO CNTRL WI BY 24/00Z PRIOR TO REACHING
   CNTRL ONTARIO BY 12Z/THURSDAY.  MEANWHILE...A TRAILING COLD FRONT
   WILL SURGE EWD THROUGH THE MID-MS VALLEY INTO UPPER GREAT LAKES AND
   OH VALLEY WITH THE TRAILING EXTENSION OF THE FRONT ADVANCING MORE
   SLOWLY INTO THE LOWER-MS VALLEY.  ELSEWHERE...AN OUTFLOW
   BOUNDARY/RESIDUAL BAROCLINIC ZONE FROM CNTRL LA TO ALONG THE MS/AL
   COASTS AND THEN NEWD THROUGH E-CNTRL GA INTO THE CAROLINA PIEDMONT
   WILL ATTEMPT TO DEVELOP NWD/NWWD IN RESPONSE TO STRENGTHENING
   LOW-LEVEL SLY WINDS.

   ...OH VALLEY INTO THE TN AND LOWER-MS VALLEYS...

   MULTIPLE BANDS OF STRONG TO SEVERE STORMS ARE ONGOING AS OF MID
   MORNING FROM SRN IL TO CNTRL AR WITH THIS ACTIVITY LIKELY BEING
   FORCED BY A COMBINATION OF LOW-LEVEL WARM THERMAL AND MOISTURE
   ADVECTIONS...AND THE LEADING EDGE OF STRONGER MID-LEVEL HEIGHT
   FALLS/DCVA DOWNSTREAM OF THE MIGRATORY SHORT-WAVE TROUGH.  WHILE
   CLOUDS WILL LIKELY REMAIN FAIRLY WIDESPREAD ACROSS THE WARM
   SECTOR...POLEWARD FLUXES OF HEAT AND MOISTURE ALONG A
   BROADENING/STRENGTHENING SWLY LLJ WILL ALLOW FOR THE AIR MASS TO
   DESTABILIZE AHEAD OF THE ONGOING STORMS.  AFTERNOON MLCAPE VALUES
   ARE EXPECTED TO RANGE FROM 250-500 J/KG ACROSS THE OH VALLEY TO AS
   HIGH AS 1500-2500 J/KG OVER THE LOWER-MS VALLEY WHERE RICHER
   LOW-LEVEL MOISTURE AND THE POTENTIAL FOR STRONGER DAYTIME HEATING
   WILL RESIDE.

   LATEST CONVECTION-ALLOWING MODEL GUIDANCE REMAINS CONSISTENT WITH
   EARLIER DATA IN SUGGESTING THAT THE BOWING STRUCTURE OVER SERN
   MO/NERN AR WILL CONTINUE NEWD ALONG THE OH RIVER WITH AN ATTENDANT
   RISK FOR POTENTIALLY WIDESPREAD DAMAGING WINDS AND EMBEDDED
   TORNADOES GIVEN THE PRESENCE OF STRONG LOW-LEVEL AND DEEP-LAYER
   SHEAR.  FARTHER SW OVER ERN AR INTO WRN TN AND NRN MS...THE
   FAVORABLE OVERLAP OF MODERATE INSTABILITY AND STRONG VERTICAL SHEAR
   WILL YIELD AN ENVIRONMENT CONDUCIVE FOR TORNADIC SUPERCELLS THIS
   AFTERNOON INTO TONIGHT WHERE THE POTENTIAL WILL EXIST FOR A FEW
   INTENSE...LONG-TRACKED TORNADOES.  THIS CONVECTIVE REGIME
   --FEATURING REGENERATIVE/BACKBUILDING STORMS-- WILL PERSIST
   OVERNIGHT FROM THE TN VALLEY INTO LOWER-MS VALLEY WHERE A CONTINUED
   RISK FOR TORNADOES AND DAMAGING WINDS WILL EXIST.  

   ...CNTRL GULF COAST INTO CAROLINA PIEDMONT...

   THE INLAND FLUX OF HIGH THETA-E AIR FROM OFF THE GULF OF MEXICO WILL
   FOSTER AN INCREASE IN TSTMS ACROSS THE REGION TODAY WITH ACTIVITY
   LARGELY BEING FOCUSED ALONG THE RESIDUAL FRONT/OUTFLOW BOUNDARY
   WHICH WILL ATTEMPT TO DEVELOP NWD/NWWD.  GIVEN THE PRESENCE OF A
   MOIST AND AT LEAST MARGINALLY UNSTABLE AIR MASS COINCIDENT WITH THE
   ERN EDGE OF STRONGER DEEP-LAYER WIND FIELDS ATTENDANT TO THE CNTRL
   U.S. SYNOPTIC SYSTEM...A RISK FOR A FEW TORNADOES AND LOCALLY
   DAMAGING WINDS WILL EXIST WITH THE MOST INTENSE STORMS.

   ...MID-MS VALLEY...

   AN ADDITIONAL BAND OF TSTMS IS EXPECTED TO DEVELOP THIS AFTERNOON
   AHEAD OF THE MIGRATORY SURFACE LOW AND TRAILING COLD FRONT FROM
   PORTIONS OF ERN MO INTO WRN IL...ALONG THE CHANNEL OF STRONGEST
   MID-LEVEL HEIGHT FALLS ATTENDING THE UPPER-AIR SYSTEM.  POCKETS OF
   STRONGER HEATING AND RESIDUAL DEWPOINTS IN THE 50S WILL YIELD MLCAPE
   OF AROUND 500 J/KG AMIDST STRONG VERTICAL SHEAR.  AS SUCH THE
   POTENTIAL WILL EXIST FOR LOW-TOPPED SUPERCELLS AND BOWING STRUCTURES
   CAPABLE OF A FEW TORNADOES...DAMAGING WINDS AND PERHAPS SOME HAIL.

   ..MEAD/GLEASON.. 12/23/2015

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z