Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 260842
SWOD48
SPC AC 260841

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0341 AM CDT Fri May 26 2017

Valid 291200Z - 031200Z

...DISCUSSION...
...Monday/Day 4 and Tuesday/Day 5...
The ECMWF and GFS solutions move an upper-level trough across the
mid to upper Mississippi Valley on Monday as a cold front advances
southeastward into the southern Plains, lower Mississippi Valley and
southern Appalachians. The models move the front southward on
Tuesday as the upper-level trough moves eastward across the Ohio and
Tennessee Valleys. An isolated severe threat will be possible along
parts of the front where instability becomes the strongest both on
Monday and Tuesday during the afternoon and evening.

...Wednesday/Day 6...
The ECMWF and GFS solutions both show strong moisture advection
across the Great Plains and lower to mid Mississippi Valley on
Wednesday. The GFS is more aggressive with moisture return and has a
less amplified upper-level trough in the Great Lakes region. This
solution would be more favorable for a severe threat in the Upper
Midwest. However, the ECMWF solution seems a little bit more
reasonable with an axis of instability from the Ozarks northward
into the mid Missouri Valley. This would suggest a severe threat
will be possible in the lower to mid Missouri Valley on Wednesday
afternoon and evening. Severe thunderstorms could also develop
southward along a dryline in the southern and central Plains.
Predictability is too low to add a severe threat area on Wednesday.

...Thursday/Day 7 and Friday/Day 8...
The ECMWF and GFS solutions are different on Thursday and Friday
especially concerning the upper-level pattern. However, both models
show a front from the mid Missouri Valley extending eastward into
the Ohio Valley/southern Great Lakes on Thursday. This could be the
favored corridor for a severe threat Thursday afternoon and evening.
On Friday, these solutions are quite different suggesting
predictability is very low late in the day 4 to 8 period.

..Broyles.. 05/26/2017



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