Day 1 Severe Weather Outlook

Valid 022000Z – 031200Z


Severe thunderstorms are possible this afternoon through early
Tuesday morning across parts of the Northern Plains and Upper
Midwest, with the most likely corridor from North Dakota to central
Minnesota and west-central Wisconsin. Other severe storms are
possible across the Northeast States, along with a low tornado risk
along the Florida east coast.

…Northern Plains and Upper Mississippi Valley…
Changes to this outlook include an east/southeast expansion in the
risk categories to include more of western Wisconsin for an
anticipated MCS and/or cluster of storms. Strong instability
continues to develop south of the warm front from SD into southern
MN. An initial cluster of storms over central ND will continue
southeastward with a damaging wind and hail threat, increasing later
this evening and overnight as the system encounter warmer air. In
addition, a tornado or two will be possible given favorable shear

For more information regarding ongoing storms over ND, see mesoscale
discussion 1913.

..Jewell.. 09/02/2019

.PREV DISCUSSION… /ISSUED 1147 AM CDT Mon Sep 02 2019/

…Dakotas/Upper Midwest…
Severe thunderstorm potential is expected to steadily increase this
afternoon into tonight, initially across the Dakotas this afternoon
and into Minnesota and western Wisconsin late this
evening/overnight, with all severe-weather-related risks possible.

A consequential shortwave trough by late-summer standards will
continue to amplify/dig southeastward over southern portions of
Alberta/Saskatchewan today, reaching the eastern Dakotas and
Minnesota tonight. Increasing mid-level height falls and
strengthening deep-layer winds will be associated with this trough,
all while a moist air mass steadily spreads northward in relation to
a northward-moving warm front across the region.

Initially, a band of mid-level warm advection will support elevated
convection spreading from northeast Montana/northwest North Dakota,
some of which may be capable of severe hail. See Mesoscale
Discussion 1911 for short-term details. It is likely that convection
will further increase in coverage/organization this afternoon while
becoming increasingly near-surface-based in closer proximity to the
warm front with an increasing damaging wind potential aside from
large hail. It appears likely that a well-organized MCS will evolve
by late afternoon/early evening.

Although some questions exist regarding the stability of the
low-level thermodynamic environment late tonight, storm
organization/forward acceleration will be influenced by a dramatic
strengthening of 850/700 mb winds. This suggests damaging wind
potential will likely further increase late this evening/early
overnight, particularly in closer proximity to the warm front, as
the MCS accelerates east-southeastward across a broad part of
central Minnesota. Damaging winds aside, this will also include some
potential for QLCS-related tornadoes along with continued severe
hail potential.

…Southern New England through northern Virginia…
Bands of convection are moving across southern New England and
northern New Jersey/southeast New York at midday. Surface-based
buoyancy will tend to remain modest where low-level hodographs will
remain modestly enlarged, but isolated damaging wind and/or brief
tornado is possible. Farther southwest, across a broader part of the
Mid-Atlantic region, isolated to scattered thunderstorms may develop
as a weaker upstream impulse shifts east from Lower Michigan and
interacts with a lee surface trough. Adequate deep-layer shear will
exist for isolated strong gusts and marginally severe hail.

…Florida Atlantic coast…
Hurricane Dorian is forecast to drift northwestward through the
period; reference NHC forecasts for the latest details. Dorian
should remain far enough offshore to limit the overall tornado
threat as typical on the western periphery of hurricanes. That said,
low-level hodographs should gain some additional length/curvature
through late today and tonight as winds strengthen along the east
coast of the Peninsula. Any cells that can develop in outer
rainbands this afternoon into tonight might pose a risk for a brief


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