Day 4-8 Outlook

Day 4-8 Outlook Image

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0358 AM CDT Fri Oct 16 2020

Valid 191200Z - 241200Z

...Monday/Day 4 to Tuesday/Day 5...
An upper-level trough is forecast to move eastward across the
central United States on Monday as a cold front advances
southeastward into the mid Mississippi and Ohio Valleys. The
medium-range models are suggesting potential for thunderstorm
development ahead of the front Monday afternoon and evening. At this
time, instability is forecast to be weak ahead of the front which
would limit the potential for severe storms.

On Tuesday, the central U.S. upper-level trough is forecast to move
into the Mississippi Valley as the front advances southward into the
Southeast. As a large area of high pressure moves into the eastern
states, moisture return will be possible across the southern Plains.
Although the models are forecasting moderate instability across
parts of Texas, capping and weak deep-layer shear should keep any
severe threat marginal across Texas Tuesday afternoon and evening.

...Wednesday/Day 6 to Friday/Day 8...
On Wednesday, the medium-range models maintain a large-scale
upper-level trough across the Mississippi Valley. A moist airmass is
forecast to advect northward from the Arklatex to the lower Ohio
Valley. Convective development will be most likely along the
instability gradient from the central Plains east-northeastward into
northern sections of the Ohio Valley. An isolated severe threat will
be possible along this corridor.

The same general area is forecast to have a continued chance of
storms on Thursday as an upper-level trough moves into the Great
Plains. The ECMWF and GFS are in good agreement with the timing of
the system and placement of the moist axis. Thunderstorms would be
most likely Thursday evening from Oklahoma northeastward into
Missouri, Illinois and Indiana. Although a severe threat will be
possible Thursday afternoon and evening, the models suggest that the
strongest instability will be located to the southwest of the
stronger mid-level flow. For this reason, predictability is low
concerning the magnitude and spatial distribution of a severe threat
Thursday afternoon and evening.

On Friday, the models move an upper-level trough eastward across the
Great Lakes as a cold front advances quickly eastward into the
eastern U.S. Thunderstorm development will be possible along the
front during the day extending into the overnight period. However,
instability is forecast to be weak which should keep any severe
threat isolated. In any case, uncertainty is substantial late in the
day 4 to 8 period.

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