Day 1 Severe Weather Outlook

Valid 302000Z – 011200Z


Isolated large hail and damaging gusts will be possible this evening
across parts of the upper Mississippi Valley.

…20Z Update…

…Western VA…Western NC…Far Western SC…
A couple of strong storms, which may briefly reach severe strength,
are possible across the higher terrain of western VA and NC. In this
region, subtle shortwave trough cresting the large upper ridge is
interacting with a backdoor front along the high terrain and
promoting isolated storm development. Low-level winds are weak but
deep northwesterly flow supports long hodographs and moderate
deep-layer shear. Given these shear profiles, a few more organized
updrafts capable of hail and/or damaging wind gusts are possible.
Eastern extent of the severe potential will limited by the wedge
front and all storm should weaken with the loss of daytime heating.

Recent surface analysis places a low over the ND/SD/MN border
intersection with a warm front extending east-southeastward through
central MN and WI and a cold front extending southwestward through
central NE. Warm sector between these fronts is characterized by
dewpoints in the upper 60s/low 70s and temperatures ranging from the
low 80s near the warm front to upper 80s/low90s across the central
Plains. Overall scenario described in the previous outlook (appended
below) remains valid. Isolated severe storms remain possible across
the Upper MS Valley and southern High Plains this afternoon and
evening as well as over the central Plains this evening through

..Mosier.. 09/30/2019

.PREV DISCUSSION… /ISSUED 1112 AM CDT Mon Sep 30 2019/

…Upper MS Valley this afternoon/evening…
Little change is expected with the larger-scale pattern, as a closed
high persists over the lower MS Valley, and a deep trough remains
over the northern Rockies and Great Basin. An embedded speed max
over WY as of late morning will eject to ND this evening and western
ON overnight, around the northwest periphery of the MS Valley high.
An associated surface low now in northeast SD will move
northeastward across MN/northwest WI by this evening, and Lake
Superior overnight, while weakening gradually.

A moist/unstable warm sector will persist today south and east of
the surface low, where boundary-layer dewpoints near 70 F and
afternoon temperatures in the 80s will contribute to MLCAPE of
2000-3000 J/kg. The majority of the warm sector will remain capped
beneath a relatively warm elevated mixed layer, and large-scale
forcing for ascent will be minimal in proximity to the surface warm
sector. Thus, storm development will depend on weak low-level
ascent near the surface low and along the trailing cold front this
evening. If surface-based storms do form along the cold front, the
environment with effective bulk shear greater than 40 kt will favor
supercells capable of producing large hail, damaging winds, and
perhaps a tornado or two (primarily near the warm front where
low-level shear/hodograph curvature will be greater).

…Central Plains this evening into early tonight…
The trailing cold front will move slowly southeastward across NE
through tonight. Surface-based storm development along the front is
in question given a largely capped warm sector. The more probable
scenario is for elevated storms to form on the cool side of the
boundary, as warm advection increases late evening atop the frontal
surface across southern NE. Elevated supercells will be possible
for a few hours early tonight, with an associated threat for large
hail/damaging winds. Storm coverage should increase through the
overnight hours, though storm intensity will likely diminish.

…Southern High Plains this afternoon/evening…
Low-level moisture from the Gulf of Mexico and mid/high-level
moisture from tropical cyclone Narda near the southern Gulf of
California will stream across the southern High Plains through
tonight. There will be some potential for gusty outflow winds with
the initial convection this afternoon/evening across eastern NM and
vicinity with marginal supercell structures, though moistening
profiles by tonight suggest that locally heavy rainfall will become
the main concern.


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