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Day 4-8 Severe Weather Outlook Issued on Dec 16, 2017
Updated: Sat Dec 16 08:49:03 UTC 2017
Day 4-8 Severe Weather Outlook Graphics Issued on Dec 16, 2017
Day 4 Severe Weather Outlook Graphics Issued on Dec 16, 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 Dec 16, 2017
Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 6 Severe Weather Outlook Graphics Issued on Dec 16, 2017
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 Dec 16, 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 Dec 16, 2017
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Tue, Dec 19, 2017 - Wed, Dec 20, 2017 D7Fri, Dec 22, 2017 - Sat, Dec 23, 2017
D5Wed, Dec 20, 2017 - Thu, Dec 21, 2017 D8Sat, Dec 23, 2017 - Sun, Dec 24, 2017
D6Thu, Dec 21, 2017 - Fri, Dec 22, 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 160847
   SPC AC 160847

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0247 AM CST Sat Dec 16 2017

   Valid 191200Z - 241200Z

   ...DISCUSSION...
   ...Tuesday/Day 4 and Wednesday/Day 5...
   The medium-range models including the ECMWF, GFS, UKMET and Canadian
   models move an upper-level trough into the southern Plains on
   Tuesday. Low-level moisture is forecast to advect northward onto the
   Texas Coastal Plains on Tuesday as thunderstorm development takes
   place ahead of the upper-level trough. Weak instability coupled with
   moderate to strong deep-layer shear could be sufficient for a
   marginal severe threat Tuesday afternoon along the middle to upper
   Texas Coast.

   On Wednesday, the upper-level trough is forecast to move eastward
   across the Gulf Coast States. Thunderstorm development will be
   possible ahead of the trough in a moist airmass from the lower
   Mississippi Valley eastward into the Carolinas. Although a marginal
   severe threat could develop on Wednesday, substantial uncertainty
   exists concerning the timing of the system and moisture return.

   ...Thursday/Day 6 to Saturday/Day 8...
   For Thursday, the four model solutions amplify an upper-level trough
   in the Southwestern States. The models vary on how fast this
   upper-level trough moves eastward with the ECMWF being the most
   progressive solution. Ahead of this system, west to southwest
   mid-level flow is forecast across the Southeast. The ECMWF shows a
   moist airmass in place on Friday from southern Mississippi eastward
   to Florida. Thunderstorm development will be possible on Friday
   afternoon along a cold front with this potential possibly moving 
   eastward into Georgia and northern Florida. Weak instability will
   probably limit any severe potential on Friday. A relatively dry
   airmass is forecast across the CONUS on Saturday which would limit
   thunderstorm potential.

   ..Broyles.. 12/16/2017

   CLICK TO GET WUUS48 PTSD48 PRODUCT
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Page last modified: December 16, 2017
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