ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 080959
   SPC AC 080959

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0359 AM CST Mon Mar 08 2021

   Valid 111200Z - 161200Z

   ...DISCUSSION...
   ...Thursday/Day 4 to Saturday/Day 6...
   The medium-range models begin the Day 4 to 8 period in good
   agreement. Model solutions show southwest mid-level flow from the
   south-central U.S. to the Northeast. An upper-level low is forecast
   over southern California. At the surface, a cold front is forecast
   to advance southeastward across the southern Plains, Ozarks and mid
   Mississippi Valley. Thunderstorm development will be possible along
   parts of the front during the afternoon and evening. Although
   instability is forecast to be weak ahead of the front Thursday
   afternoon, strong deep-layer shear should be adequate for at least
   isolated severe storms. The severe threat should extend from
   northwest Texas northeastward across the Ozarks and into the lower
   Ohio Valley. Hail and wind damage will be the primary threats.

   On Friday, the models continue to be in good agreement. The
   solutions move the upper-level low into the Desert Southwest and
   have an upper-level ridge in the south-central states. The cold
   front is forecast to move slowly southward and may stall from the
   southern Plains eastward into the mid Mississippi Valley during the
   day on Friday. Model forecasts suggest that thunderstorm development
   will be possible along and near the front during the afternoon and
   evening. The greatest potential for severe storms would be from
   Oklahoma eastward into Arkansas, where low-level moisture, deep
   layer shear and instability are forecast to be maximized.

   Although there is some spread among the GEFS members, on Saturday
   the deterministic solutions remain in relatively good agreement. The
   upper-level low is forecast to move into the Four Corners region as
   a mid-level jet moves into the southern Plains. Ahead of the
   approaching system, strong moisture advection is forecast in the
   southern Plains where a corridor of 60+ surface dewpoints appears
   likely by afternoon. Thunderstorms should be ongoing across parts of
   the southern Plains and Ozarks throughout the day. An increase in
   thunderstorm coverage may take place in the late afternoon and
   evening as instability maximizes across the region. Model forecasts
   show a potential for moderate instability, widespread large-scale
   ascent and strong deep-layer shear from the southern Plains eastward
   into the Ozarks. All severe threat hazards will be possible, but the
   magnitude and spatial extent of the severe threat will depend upon
   moisture return and the eastward timing of the system. 

   ...Sunday/Day 7 and Monday/Day 8...
   On Sunday and Monday, the upper-level low is forecast to move
   eastward across the Great Plains. At the surface, a cold front is
   forecast to move quickly eastward from the Great Plains into the
   Ohio and Tennessee Valleys. Severe thunderstorms will be possible
   along parts of the front both on Sunday and on Monday. At this time,
   models suggest that the greatest severe threat will be located in
   eastern parts of the southern Plains and in the Ozarks on Sunday.
   The severe threat should shift eastward into the Ohio and Tennessee
   Valleys on Monday. However, uncertainty concerning the timing of the
   system is substantial at this extended range in the forecast period.

   ..Broyles.. 03/08/2021

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