Severe Storm Outlook Narrative (AC)
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000
ACUS48 KWNS 280857
SWOD48
SPC AC 280855

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0355 AM CDT Sun May 28 2017

Valid 311200Z - 051200Z

...DISCUSSION...
...Wednesday/Day 4 and Thursday/Day 5...
The ECMWF and GFS solutions are in reasonable agreement on Wednesday
with an upper-level trough in the Great Lakes and an upper-level
ridge in the central and northern Rockies. Both models show a moist
sector from the southern and central Plains into the Gulf Coast
States. Organized convection may occur on Wednesday afternoon and
evening from parts of western and central Texas northward into
Oklahoma and Kansas but the upper-level ridge will probably suppress
the severe threat some. Both solutions advect low-level moisture
quickly northward across the mid Missouri and mid to upper
Mississippi Valleys on Thursday. A severe threat seems possible
Thursday afternoon and evening on the northern part of the corridor
of low-level moisture from eastern Nebraska and eastern South Dakota
eastward into southern Minnesota and Iowa. Spatial uncertainty is
still too high to warrant adding a severe threat area for Wednesday
and Thursday.

...Friday/Day 6 to Sunday/Day 8...
The ECMWF and GFS solutions show a lot of spread by Friday but do
have a moist airmass still in place across the north-central states.
If these solutions are somewhat close to correct, a severe threat
would be possible along the moisture gradient from the Dakotas
eastward into the southern Great Lakes Friday afternoon and evening.
On Saturday, the two solutions develop an upper-level trough in the
Great Lakes and appear to show a front from the southern plains
northeastward into the mid to upper Mississippi Valley. If these
solutions are somewhat close to being correct, a severe threat would
be possible along this corridor on Saturday afternoon and evening.
Model differences on Sunday are substantial. Predictability
concerning exact scenarios remains low throughout the day 4 to 8
period.

..Broyles.. 05/28/2017


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