Dec 21, 2014 0830 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sun Dec 21 08:30:54 UTC 2014 (20141221 0830Z Day 3 shapefile | 20141221 0830Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
0830 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 90,164 8,280,369 New Orleans, LA...St. Petersburg, FL...Baton Rouge, LA...Mobile, AL...Jackson, MS...
MARGINAL 74,168 11,324,795 Jacksonville, FL...Tampa, FL...Orlando, FL...Montgomery, AL...Gainesville, FL...
Probabilistic Graphic
20141221 0830 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 90,969 8,382,359 New Orleans, LA...St. Petersburg, FL...Baton Rouge, LA...Mobile, AL...Jackson, MS...
5 % 73,103 11,277,954 Jacksonville, FL...Tampa, FL...Orlando, FL...Montgomery, AL...Gainesville, FL...
   SPC AC 210830

   DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0230 AM CST SUN DEC 21 2014

   VALID 231200Z - 241200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
   THE GULF COASTAL REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER THE LOWER MS VALLEY INTO A
   PORTION OF THE SERN STATES AND NRN FL...

   ...SUMMARY...
   POTENTIAL WILL EXIST FOR A FEW STRONG TO SEVERE THUNDERSTORMS FROM
   SOUTHERN PORTIONS OF THE LOWER MISSISSIPPI VALLEY THROUGH THE GULF
   COASTAL REGION TUESDAY INTO TUESDAY NIGHT. THE PRIMARY THREATS WILL
   BE ISOLATED DAMAGING WIND GUSTS AND A COUPLE OF TORNADOES. SOME HAIL
   WILL ALSO BE POSSIBLE...MAINLY OVER THE LOWER MISSISSIPPI VALLEY
   REGION.

   ...SYNOPSIS...

   HIGH-AMPLITUDE UPPER TROUGH WILL ADVANCE SLOWLY THROUGH THE PLAINS
   WITH AN EMBEDDED SRN STREAM SHORTWAVE TROUGH REACHING THE LOWER MS
   VALLEY REGION TUESDAY NIGHT. PRIMARY SFC CYCLONE ATTENDANT TO THE
   NRN-STREAM SHORTWAVE TROUGH WILL WEAKEN AS IT MOVES TOWARD THE WRN
   GREAT LAKES. THE TRAILING COLD FRONT WILL CONTINUE THROUGH THE MS
   VALLEY AND LIKELY EXTEND FROM THE GREAT LAKES SWD INTO AL BY THE END
   OF THIS PERIOD. WEAK CYCLOGENESIS WILL ALSO BE POSSIBLE IN
   ASSOCIATION WITH THE SRN-STREAM IMPULSE...AND THIS FEATURE SHOULD
   LIFT NEWD ALONG THE FRONT THROUGH MS INTO THE TN VALLEY OVERNIGHT. A
   WARM FRONT SHOULD STALL OVER THE GULF COAST REGION. 

   ...LOWER MS VALLEY THROUGH THE GULF COASTAL REGION AND NRN FL...

   PRIMARY COMPLICATING FACTOR THIS FORECAST IS POTENTIAL FOR NUMEROUS
   SHOWERS AND THUNDERSTORMS TO DEVELOP EARLY IN PERIOD OVER A PORTION
   OF THE SERN STATES WITHIN ZONE OF ISENTROPIC ASCENT ALONG AND NORTH
   OF COASTAL FRONT. THIS SHOULD LIMIT BOUNDARY-LAYER DESTABILIZATION
   POTENTIAL WITH NWD EXTENT AWAY FROM THE GULF COAST. GREATEST CAPE
   EARLY TUESDAY IS LIKELY OVER LA AND SRN MS WHERE REMNANT EML WILL
   HAVE ADVECTED ABOVE WRN FRINGE OF THE MOIST AXIS. MUCAPE IN THIS
   REGION MAY APPROACH 1500 J/KG. STORMS WILL LIKELY INCREASE DURING
   THE DAY ALONG AND NORTH OF THE WARM FRONT FROM THE GULF COAST AREA
   NWD INTO THE SERN STATES PROMOTED BY A BROAD SLY LLJ. GIVEN
   EFFECTIVE SHEAR FROM 40-50 KT...POTENTIAL WILL EXIST FOR A FEW
   SUPERCELLS...AND STORMS MAY BECOME ROOTED NEAR THE SFC OVER SRN
   PORTIONS OF THE LOWER MS VALLEY AND GULF COAST REGION. OTHER STORMS
   MAY DEVELOP AS SEWD ADVANCING FRONT INTERCEPTS THE MOIST AXIS.
   ACTIVITY WILL DEVELOP EWD DURING THE DAY AND OVERNIGHT THROUGH THE
   SERN STATES AND GULF OF MEXICO AND EVENTUALLY INTO NRN FL. WILL
   MAINTAIN A LOWER-END SLIGHT RISK THIS UPDATE GIVEN THE CONDITIONAL
   NATURE OF THE THREAT.

   ..DIAL.. 12/21/2014

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0830Z