Day 1 Severe Weather Outlook

Valid 171200Z – 181200Z


Severe storms are expected over parts of the northern and central
Plains into thee upper Midwest later this afternoon into tonight. A
few strong storms are also possible from the Ohio Valley into
western New England.


…Northern Plains and upper MS Valley region…

Upper trough over western Canada will undergo significant
amplification as it advances eastward today. A cold front will
accompany this feature through the northern Plains. By 12Z the front
will extend from eastern ND southwest into western SD. By early
evening the front should stretch from northwest MN into southwestern
SD. This region will reside along the northern fringe of the steeper
mid-level lapse rates. Low to mid 60s F dewpoints will reside in
warm sector, and diabatic heating should boost MLCAPE to 2000-2500
J/kg. Forcing for ascent accompanying the amplifying upper trough
will overtake the frontal zone and storms should develop and
intensify along the southeast- advancing cold front during the
afternoon from eastern ND into central and southwest SD.
Strengthening winds aloft will support 40-45 kt effective bulk shear
in frontal zone and some supercell structures appear likely across
SD with large hail and damaging wind the main threats, through a
couple of tornadoes will also be possible. Storms may evolve into
line segments as they develop eastward toward the MS valley with a
continued severe threat into the evening.

…Middle Mississippi Valley region…

Widespread storms developing tonight will reinforce the front across
KS and northern MO. This activity may be ongoing across KS and MO at
the start of this period, but should decrease in coverage as it
shifts east toward the OH Valley. This reinforced front may develop
north during the day, but considerable uncertainty remains where
this boundary will reside by 00Z. The warm sector south of and in
vicinity of this boundary will become strongly unstable with
2500-3500 J/kg MLCAPE. Timing and placement of redevelopment of
storms along this boundary is uncertain, but current thinking is
that the atmosphere will probably remain capped to surface-based
storms until evening when the low-level jet will augment isentropic
ascent along and north of this feature. Storms should redevelop
anywhere from northeast KS, eastern NE into IA where the environment
will support supercells capable of mainly large hail, but a few
tornadoes will also be possible if development occurs before the
boundary layer decouples. Activity may grow upscale into an MCS and
continue eastward into northern IL overnight with a continued threat
for mainly damaging wind.

…Central Plains…

Deep mixing in vicinity of trough/dryline feature will once again
support high-based storms from the TX Panhandle into western OK and
southern KS with primary threat being isolated damaging wind and

Other storms are expected to develop over the higher terrain or
along a dryline from eastern CO into southeast WY and spread east
into the corridor of moderate instability during the afternoon and
evening. Isolated damaging wind and large hail will be possible with
this activity.

…Ohio Valley region…

An MCV from ongoing storms over the Middle MS Valley will continue
into the OH Valley during the day where moderate instability and
30-35 kt deep layer flow will reside. Storms may intensify during
and afternoon and become capable of producing isolated damaging wind

..Dial/Nauslar.. 08/17/2019


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