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Day 4-8 Severe Weather Outlook Issued on Mar 20, 2017
Updated: Mon Mar 20 08:31:02 UTC 2017
Day 4-8 Severe Weather Outlook Graphics Issued on Mar 20, 2017
Day 4 Severe Weather Outlook Graphics Issued on Mar 20, 2017
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 Mar 20, 2017
Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 167,771 15,889,780 Dallas, TX...Memphis, TN...Fort Worth, TX...Arlington, TX...Plano, TX...
Day 6 Severe Weather Outlook Graphics Issued on Mar 20, 2017
Day 6 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 122,883 10,704,145 Birmingham, AL...Montgomery, AL...Mobile, AL...Columbus, GA...Jackson, MS...
Day 7 Severe Weather Outlook Graphics Issued on Mar 20, 2017
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 Mar 20, 2017
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Thu, Mar 23, 2017 - Fri, Mar 24, 2017 D7Sun, Mar 26, 2017 - Mon, Mar 27, 2017
D5Fri, Mar 24, 2017 - Sat, Mar 25, 2017 D8Mon, Mar 27, 2017 - Tue, Mar 28, 2017
D6Sat, Mar 25, 2017 - Sun, Mar 26, 2017 (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 200828
   SPC AC 200828

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0328 AM CDT Mon Mar 20 2017

   Valid 231200Z - 281200Z

   ...DISCUSSION...
   ...Day 4 to Day 6...
   The medium-range models begin the day 4 to 8 period with an
   upper-level ridge in the central U.S. and an upper-level trough over
   Baja California. This system is forecast to move quickly
   northeastward across the Desert Southwest and into the southern
   Rockies on Thursday/Day 4. A dryline is forecast to setup in the
   southern and central High Plains by late afternoon where isolated
   severe thunderstorms will be possible into the evening. However,
   will not add a severe threat area yet due to uncertainties
   concerning the quality of moisture return and exact timing of
   large-scale ascent entering the high Plains Thursday evening.

   The dryline is forecast to sharpen on Friday/Day 5 and move eastward
   across the southern Plains during the day. The best chance for
   thunderstorm initiation would be in the late afternoon from
   east-central Oklahoma south southwestward into the north-central to
   northeast Texas. The ECMWF and GFS solutions are in good agreement
   with this scenario and the models provide support for the idea of a
   line of thunderstorms organizing into a wind producing linear MCS.
   If this where to occur based on the timing of the models, a line of
   storms would move east southeastward across the Arklatex Friday
   evening, into the lower Mississippi Valley overnight crossing the
   central Gulf Coast States during day on Saturday/Day 6. Based on
   this scenario, will maintain a 15 percent contour from eastern parts
   of the southern Plains into the Arklatex. Will expand this area
   eastward into the lower Mississippi Valley and add a new 15 percent
   contour in the central to eastern Gulf Coast States for Day 6.

   ...Day 7 to Day 8...
   On Sunday/Day 7 and Monday/Day 8, large differences exist between
   the ECMWF and GFS solutions. The ECMWF emphasizes the development of
   a negatively tilted upper-level trough in the southern and central
   Plains while the GFS emphasizes the upper-level trough just upstream
   from the Carolinas. A severe threat could develop ahead of either of
   these two systems. However, due to large model differences,
   uncertainty is too great to warrant adding a 15 percent area late in
   the forecast period.

   ..Broyles.. 03/20/2017

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Page last modified: March 20, 2017
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