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Day 4-8 Severe Weather Outlook Issued on Apr 6, 2015
Updated: Mon Apr 6 09:03:02 UTC 2015
Day 4-8 Severe Weather Outlook Graphics Issued on Apr 6, 2015
Day 4 Severe Weather Outlook Graphics Issued on Apr 6, 2015
Day 4 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
30 % 48,934 5,438,123 St. Louis, MO...Springfield, IL...Peoria, IL...Decatur, IL...Champaign, IL...
15 % 241,503 33,655,786 Chicago, IL...Dallas, TX...Indianapolis, IN...Memphis, TN...Arlington, TX...
Day 5 Severe Weather Outlook Graphics Issued on Apr 6, 2015
Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 110,325 27,325,017 Baltimore, MD...Charlotte, NC...Washington, DC...Raleigh, NC...Norfolk, VA...
Day 6 Severe Weather Outlook Graphics Issued on Apr 6, 2015
Day 6 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 7 Severe Weather Outlook Graphics Issued on Apr 6, 2015
Day 7 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 8 Severe Weather Outlook Graphics Issued on Apr 6, 2015
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Thu, Apr 09, 2015 - Fri, Apr 10, 2015 D7Sun, Apr 12, 2015 - Mon, Apr 13, 2015
D5Fri, Apr 10, 2015 - Sat, Apr 11, 2015 D8Mon, Apr 13, 2015 - Tue, Apr 14, 2015
D6Sat, Apr 11, 2015 - Sun, Apr 12, 2015 (All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
 Forecast Discussion

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 060901
   SPC AC 060901

   DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0401 AM CDT MON APR 06 2015

   VALID 091200Z - 141200Z

   ...DISCUSSION...
   LATEST RUNS OF THE MEDIUM-RANGE MODELS EXHIBIT GOOD
   LARGE/BROAD-SCALE AGREEMENT ON LOCATIONS OF MAJOR FEATURES --
   THROUGH MUCH IF NOT ALL OF THE PERIOD.  HAVING SAID
   THAT...DIFFERENCES -- EVEN AT THE START OF THE PERIOD -- AT SMALLER
   SCALES WITH RESPECT TO BOTH INTENSITY AS WELL AS AREAL/TEMPORAL
   OFFSETS OF FEATURES PRESENTS SUBSTANTIAL CHALLENGES WITH RESPECT TO
   THE CONVECTIVE FORECAST.

   ONGOING -- AND POSSIBLY WIDESPREAD -- CONVECTION IS EXPECTED AT THE
   START OF THE DAY 4 PERIOD /THU 4-9/...ACROSS A LARGE CORRIDOR LIKELY
   TO BE CENTERED OVER THE MIDWEST/UPPER MIDWEST AREA IN ZONE OF STRONG
   WARM ADVECTION.  THE LOCATION/COVERAGE/LONGEVITY OF THIS CONVECTION
   -- DEPICTED QUITE DIFFERENTLY BY THE ECMWF AS COMPARED TO THE GFS --
   WILL LIKELY HAVE SIGNIFICANT IMPACT ON DAY 4 CONVECTIVE/SEVERE
   POTENTIAL.  

   ATTM...IT APPEARS THAT REDEVELOPMENT OF STORMS /IN THE WAKE OF
   EARLIER CONVECTION/ ALONG THE ADVANCING COLD FRONT WILL OCCUR. 
   THOUGH INSTABILITY IN MANY AREAS WILL LIKELY BE LESSER DUE TO PRIOR
   CONVECTIVE OVERTURNING...STRONG ASCENT ALONG THE FRONT COMBINED WITH
   STRONG SHEAR WITHIN WHAT SHOULD BE AN AMPLY UNSTABLE PRE-FRONTAL
   AFTERNOON ENVIRONMENT SUGGEST WIDESPREAD RISK FOR HAIL AND DAMAGING
   WINDS.  TORNADO RISK REMAINS MORE UNCERTAIN GIVEN MODEL
   DIFFERENCES...BUT WOULD BE MAXIMIZED ACROSS THE IL/ERN MO VICINITY
   PER GFS FORECASTS OF A MUCH STRONGER SURFACE LOW AND
   ASSOCIATED/BACKED LOW-LEVEL FLOW...PLUS LIKELY PRESENCE OF A PRIOR
   CONVECTIVE BOUNDARY ACROSS THE AREA.

   THE FRONT SHOULD CONTINUE RAPID EWD MOVEMENT ACROSS THE OH/TN
   VALLEYS OVERNIGHT...AND ATTM IS EXPECTED TO CROSS THE APPALACHIANS
   THROUGH LATE AFTERNOON DAY 5 /FRI 4-10/.  WITH AN AMPLY UNSTABLE AND
   SUFFICIENTLY SHEARED ENVIRONMENT LIKELY TO EXIST IN LEE OF THE
   MOUNTAINS...SCATTERED CONVECTION WITH ATTENDANT HAIL/WIND RISK
   APPEARS POSSIBLE.

   BEYOND DAY 5...THE FRONT IS PROGGED TO MOVE OFF THE ATLANTIC AND
   GULF COASTS...WITH ANY APPRECIABLE SEVERE RISK CONFINED TO POSSIBLY
   S TX -- THOUGH AN UNCERTAIN SCENARIO ATTM.  THROUGH THE LATTER
   STAGES OF THE PERIOD...A SRN-STREAM LOW/TROUGH ADVANCE  ACROSS THE
   SOUTHWEST/SRN ROCKIES AND ADJACENT NRN MEXICO IS DEPICTED...AND
   MOISTURE RETURN/AIRMASS DESTABILIZATION AHEAD OF THIS FEATURE /AND
   ASSOCIATED LEE SURFACE TROUGHING/ MAY YIELD AN INCREASE IN
   CONVECTIVE RISK INTO THE SRN PLAINS VICINITY LATE IN THE PERIOD.

   ..GOSS.. 04/06/2015

   CLICK TO GET WUUS48 PTSD48 PRODUCT
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Page last modified: April 06, 2015
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