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ACUS01 KWNS 281317
SWODY1
SPC AC 281316
Day 1 Convective Outlook RESENT 1
NWS Storm Prediction Center Norman OK
0816 AM CDT Thu Jun 28 2018
Valid 281300Z - 291200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS FAR
EASTERN MONTANA...MUCH OF WESTERN AND CENTRAL NORTH DAKOTA...AND FAR
NORTHERN SOUTH DAKOTA...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHERN PLAINS TO THE UPPER MIDWEST AS WELL AS THE MISSOURI VALLEY
AND SOUTHEAST STATES...
...SUMMARY...
Severe thunderstorms are likely across the northern Plains,
especially this afternoon and tonight, with the potential for very
large hail, tornadoes, and widespread damaging winds. Other severe
storms can be expected across the middle to lower Missouri Valley
and the Southeast States.
...Northern Plains and Upper Midwest...
Multiple rounds of severe storms are likely today, featuring
multiple storm modes including daytime into evening
supercell-related severe risks, and the possibility of an
upscale-growing significant and potentially widespread quasi-linear
MCS tonight. Accordingly, parts of eastern Montana, western and
central North Dakota, and far northern South Dakota have been
upgraded to a categorical Moderate Risk.
An initial early-day concern exists mainly across southern North
Dakota and nearby South Dakota in vicinity of a residual front,
although at least a conditional severe weather risk will exist today
as far east as northern Minnesota in vicinity of the boundary.
Reference Mesoscale Discussion 915 for additional details on today's
early-day severe threat across the region.
A warm front will otherwise lift northward towards the Canadian
border through the day. Meanwhile, a cold front will begin to
accelerate southeast over central Montana during the evening hours.
Between these two surface features, southeasterly flow will
transport mid/upper 60s dew points over the western Dakotas and into
eastern Montana. Closer to the trough/cooler temperatures aloft,
convection should initiate near/ahead of the cold front over the
higher terrain of Montana. Here, steep mid-level lapse rates and
strong effective shear will likely yield some supercells and/or
bowing segments, capable of large hail and damaging winds during the
afternoon and evening.
Convergence near the warm front and amplifying large-scale ascent
will likely promote a rapid increase in storm coverage through the
evening and early overnight over eastern Montana and western/central
North Dakota. Storms should rapidly become severe, owing to strong
buoyancy characterized by MLCAPE values of 3000-3500+ J/kg.
Organized by veering flow with height, initial cells will likely be supercellular, capable of very large hail, damaging winds, and a
couple tornadoes. Expected upscale growth into one or more eastward-accelerating convective systems is anticipated (50+ kt
forward motion probable) tonight, with a potentially significant
swath of damaging winds possible.
...Middle/Lower Missouri Valley to Middle Mississippi Valley...
Although the degree of mid-level warmth/capping provides some
uncertainty, a weak mid-level impulse/MCV may continue to support at
least isolated severe thunderstorms today from eastern Nebraska into
Iowa and northern Missouri within a very unstable environment along
a WNW/ESE-oriented frontal zone. Damaging winds and large hail can
be expected. Reference Mesoscale Discussion 914 for additional
details.
...Southern Appalachians to Southeast States...
Relatively minimal cloud cover and steady diurnal destabilization to
the south-southwest of ongoing storms across the southern
Appalachians will allow for an increase in surface-based storms by
afternoon, especially spanning parts of Tennessee into Alabama and
Georgia. Somewhat enhanced mid-level winds could for modest storm
organization of generally southward moving storm clusters. Damaging
winds will be the most common hazard this afternoon through early
evening, although some hail could occur as well.
...Northeast States...
A warm front will lift northeast across New England this morning,
with weak instability/surface-based buoyancy spreading northeastward
in tandem. Warm advection should yield a few showers/thunderstorms
through the morning hours, and a threat may exist for a brief
tornado or localized damaging gusts, owing to enhanced low-level
shear and moist/neutral boundary-layer profiles. A few stronger
storms may also develop through mid-day/afternoon, as the main
shortwave impulse crosses the region and offers some focus for
stronger convection along a surface trough.
..Guyer/Marsh.. 06/28/2018
$$
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