Severe Storm Outlook Narrative (AC)
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461
ACUS48 KWNS 290849
SWOD48
SPC AC 290848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Mon May 29 2017

Valid 011200Z - 061200Z

...DISCUSSION...
...Thursday/Day 4 and Friday/Day 5...
The ECMWF and GFS models are in reasonable agreement on Thursday
with an upper-level ridge in the central and northern high Plains, a
subtle upper-level trough in the southern Plains, and another
upper-level trough in the Great Lakes. These two solutions show a
corridor of low-level moisture from eastern parts of the Great
Plains into the Mississippi Valley. Both models show a somewhat
similar synoptic setup in place on Friday. Although the upper-level
pattern may not be conducive for a lot of severe storms, an isolated
severe threat would be possible across parts of the Great Plains and
Upper Midwest on each afternoon and evening for Thursday and Friday.
Spatial uncertainty is considerable for these two days.

...Saturday/Day 6 to Monday/Day 8...
On Saturday, the ECMWF and GFS solutions diverge, with the ECMWF
showing an upper-level trough in the Great Lakes and mid Mississippi
Valley while the GFS keeps an upper-level trough in the southern
Plains. The two solutions show more agreement at low-levels with a
broad moist sector from the Great Plains eastward to the Carolinas.
A potential for isolated severe storms would appear to be greatest
along the western moisture gradient in the Great Plains and along
the northern moisture gradient from the Upper Midwest
east-southeastward to the Mid-Atlantic on Saturday afternoon and
evening. Model spreads widen considerably for Sunday and Monday
suggesting predictability is very low for late in the day 4 to 8
period.

..Broyles.. 05/29/2017



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