(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 240751
SPC AC 240751
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 AM CDT Sat Jun 24 2017
Valid 271200Z - 021200Z
On D4/Tue, shortwave ridging will move quickly eastward across the
northern Plains with a 30-40 kt midlevel speed max moving into the
area by late in the day. High pressure will remain centered over the
mid Mississippi and Ohio valleys, with southerly flow across the
plains bringing near 60 dewpoints northward into the Dakotas ahead
of a surface low. MUCAPE around 1000-1500 J/kg is expected, with
scattered storms by late afternoon from the central Dakotas into
Nebraska. Given the progressive upper trough and an increasing
low-level jet, storms are expected to persist at least through
evening, with hail and wind possible.
By early D5/Wed, the upper disturbance will be located near the
Mississippi river, and will continue eastward across the upper Great
Lakes. By this time, the surface low will be over western Ontario,
but moisture will have increased across the Minnesota, Wisconsin and
Iowa with mid to upper 60s dewpoints. Given that storms will be
ongoing, predictability is too low to denote a D5 area, although an
eventual Slight Risk appears possible in later outlooks.
From D6/Thu and beyond, as broad belt of modest zonal flow aloft
will remain across the northern tiers of states, and large,
broadening moist sector will develop south of the synoptic front
which will extend roughly from northern Nebraska eastward into New
England. While sporadic clusters of storms are possible along this
general zone, predictability will remain low.
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