Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 250854
SPC AC 250853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Sun Jun 25 2017

Valid 281200Z - 031200Z

Various model solutions are in relatively good agreement with the
pattern through the D8 period, but the pattern itself lends
considerable uncertainty to the severe thunderstorm forecast.

On D4/Wed, a low-amplitude shortwave trough will exist across the
upper MS Valley, with substantial rain and storm activity ongoing
Wed morning, supported by a broad southwesterly low-level jet. Some
of this activity could potentially be severe, with damaging winds
the main threat. In the wake of this activity, further development
is likely along the weak cold front from MN into KS with the bulk of
the heating west of the MO river. While some additional wind or hail
threat will exist, predictability is too low to denote any areas.

The pattern will remain zonal on D5/Thu, with another shortwave
trough affecting the northern Plains. By this time, the main
synoptic boundary will stretch west-east from Nebraska into the
Northeast. The upper trough from the previous day will now be
approaching the lower Great Lakes by Thu evening, and strong
southwesterly flow will bring modest levels of instability and
moisture across the OH Valley and into western PA and NY. Sufficient
mean winds may support a few storms capable of damaging wind;
however, the threat does not appear great enough to denote a D5 area
given marginal instability coupled with low predictability.

Similarly, while clusters of strong to severe thunderstorms are
possible late D5/Thu and into the night somewhere between NE and IL
with a late shortwave trough, predictability is low.

For D6/Fri and beyond, a vast area of moisture and instability will
remain across the southeast quarter of the CONUS, with potential
areas of severe weather from the mid MS Valley on D6/Fri spreading
into the Northeast by D7/Sat. In any event, these severe
thunderstorm scenarios do not appear particularly significant.

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