Skip Navigation Links 
NOAA logo-Select to go to the NOAA homepage NOAA's National Weather Service   Select to go to the NWS homepage
Storm Prediction Center
navigation bar left  
  navigation bar end cap is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.

< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Jul 17, 2018
Updated: Tue Jul 17 07:37:03 UTC 2018
D4-8 D4 D5 D6 D7 D8
 Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions

D4Fri, Jul 20, 2018 - Sat, Jul 21, 2018 D7Mon, Jul 23, 2018 - Tue, Jul 24, 2018
D5Sat, Jul 21, 2018 - Sun, Jul 22, 2018 D8Tue, Jul 24, 2018 - Wed, Jul 25, 2018
D6Sun, Jul 22, 2018 - Mon, Jul 23, 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

   ACUS48 KWNS 170735
   SPC AC 170735

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0235 AM CDT Tue Jul 17 2018

   Valid 201200Z - 251200Z

   ...Friday/Day 4 and Saturday/Day 5...
   The medium-range models are in much better agreement early in the
   Day 4 to 8 period. The ECMWF, GFS, Canadian and UKMET move an
   upper-level trough across the mid Mississippi Valley on Friday and
   show the moist sector in the base of the trough. This would imply
   that moderate instability will be in place by Friday afternoon
   across parts of Missouri and Arkansas extending eastward into
   western parts of the Ohio and Tennessee Valleys. An isolated severe
   threat would be possible Friday afternoon along the northern edge of
   the strongest instability from near St. Louis, MO eastward to the
   Cincinnati, OH area. For Saturday, the models move the upper-level
   trough slowly eastward and again show the moist sector in the base
   of the system. The models would suggest an isolated severe threat
   will be possible across parts of the Ohio and Tennessee Valleys
   Saturday afternoon. Any severe threat would be probably remain
   marginal due to the relatively weak deep-layer shear forecast.

   ...Sunday/Day 6 to Tuesday/Day 8...
   The models continue to move the upper-level trough slowly eastward
   across the eastern U.S. from Sunday to Tuesday. Thunderstorms would
   be possible each day from near the upper-level trough eastward
   across the moist sector. For Sunday, the greatest potential for a
   marginal severe threat would be in the central Appalachians. The
   threat would shift eastward into the Mid-Atlantic on Monday and
   appears likely to diminish by Tuesday as the upper-level trough
   becomes less amplified. Also, a marginal severe threat can not be
   ruled out in parts of the central and northern Plains from Sunday to
   Tuesday but model spread is large and forecast uncertainty is high.

   ..Broyles.. 07/17/2018


To retrieve previous Day 4-8 convective outlooks, enter the date YYYYMMDD (e.g., 20050310 for March 10, 2005.)
Data available since March 8, 2005.
Weather Topics:
Watches, Mesoscale Discussions, Outlooks, Fire Weather, All Products, Contact Us

NOAA / National Weather Service
National Centers for Environmental Prediction
Storm Prediction Center
120 David L. Boren Blvd.
Norman, OK 73072 U.S.A.
Page last modified: July 17, 2018
Information Quality
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities