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Day 4-8 Severe Weather Outlook Issued on Apr 9, 2018
Updated: Mon Apr 9 08:41:03 UTC 2018
Day 4-8 Severe Weather Outlook Graphics Issued on Apr 9, 2018
Day 4 Severe Weather Outlook Graphics Issued on Apr 9, 2018
Day 4 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 5 Severe Weather Outlook Graphics Issued on Apr 9, 2018
Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 137,279 7,246,538 Shreveport, LA...Little Rock, AR...Springfield, MO...Tyler, TX...Fort Smith, AR...
Day 6 Severe Weather Outlook Graphics Issued on Apr 9, 2018
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 9, 2018
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 9, 2018
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Thu, Apr 12, 2018 - Fri, Apr 13, 2018 D7Sun, Apr 15, 2018 - Mon, Apr 16, 2018
D5Fri, Apr 13, 2018 - Sat, Apr 14, 2018 D8Mon, Apr 16, 2018 - Tue, Apr 17, 2018
D6Sat, Apr 14, 2018 - Sun, Apr 15, 2018 (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 090839
   SPC AC 090839

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0339 AM CDT Mon Apr 09 2018

   Valid 121200Z - 171200Z

   ...DISCUSSION...
   The main focus of the extended period continues to be the impressive
   amplification of a mid/upper trough over the central US late this
   week into the weekend. Along the base of the trough, an approximate
   100-kt west/southwesterly 500-mb jet will overspread the
   southern/central Plains on D5/Fri, transporting a broad area of
   relatively steep lapse rates across the region. Concurrently, a
   deepening low over the central US will encourage a narrow corridor
   of enhanced poleward moisture return (generally characterized by
   surface dew points in the 60s) from eastern Texas to the lower
   Missouri Valley. Attendant to this low, a dry line and cold front
   will accelerate eastward from the Plains towards the Mississippi
   Valley through Friday night, promoting thunderstorm activity from
   the western Gulf Coast to the Midwest.

   While still exhibiting diversity in the timing of the eastward
   evolution of the trough, medium-range guidance continues to
   highlight areas from eastern Texas to the Mid-South for the highest
   probability of severe weather late Friday into the overnight. Here,
   deterministic/ensemble guidance indicates robust wind fields will
   overlap adequate surface-based buoyancy for the development of
   severe thunderstorms. Considering the magnitude of forcing for
   ascent and the forecast meridional nature of deep-layer flow,
   upscale growth into larger convective complexes appears probable.
   Such evolution should enhance the ability of severe convection to
   spread east overnight; therefore, the ongoing 15-percent area has
   been expanded slightly towards the Mississippi Valley.

   Farther north towards the lower Missouri and mid Mississippi
   Valleys, guidance also indicates a possibility for severe
   convection. However, a narrowing moist/warm sector towards the
   primary surface low yields greater uncertainty with the spatial
   placement of such convection during the afternoon/evening. In turn,
   15-percent probabilities have not been expanded northward with this
   cycle, but could be in later updates.

   Beyond D5/Fri, timing of the eastward progression of the trough and
   associated convection remains quite uncertain. Furthermore,
   lessening buoyancy with eastward extent suggests stronger convection
   will likely remain focused near the corridor of greatest deep
   ascent, magnifying concerns regarding temporal uncertainty.
   Subsequently, predictability too low is maintained through the
   remainder of the extended period.

   ..Picca.. 04/09/2018

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Page last modified: April 09, 2018
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