Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 130600
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Sun May 13 2018
Valid 131200Z - 141200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
THE SOUTHERN PLAINS AND THE MIDWEST...
A few strong to severe thunderstorms are possible today from parts
of the Midwest to the Mid Atlantic, the southern/central Plains, and
a portion of the Colorado Front Range into the Laramie Mountains
vicinity of Wyoming. Damaging wind and hail will be the primary
A synoptic blocking pattern will persist today with cutoff upper low
over the Great Basin and Intermountain West and a downstream upper
ridge over the Southeast States. At the surface a quasi-stationary
front will persist from eastern VA through the OH Valley and west
into KS where it will intersect a dryline extending south through
Richer low-level moisture with mid-upper 60s F surface dewpoints
will advect through the warm sector to the south of a
quasi-stationary front currently situated from the OH Valley through
northern MO. A warm elevated mixed layer will expand east above the
moistening warm sector and frontal zone contributing to very strong
instability (2000-3000 J/kg MUCAPE) and a strong cap. Shortwave
ridging and strong convective inhibition should limit thunderstorm
development over much of this region during the day. However
vorticity maximum currently approaching the southern Rockies will
crest upper ridge this evening and tonight which, along with a
strengthening low-level jet, should contribute to sufficient
isentropic ascent for storms to initiate along/north of the front.
Most CAM solutions suggest this activity will eventually grow
upscale, possibly becoming a forward propagating MCS. Initial threat
will be large hail across IA, but the threat for damaging wind may
increase as storms grow upscale from eastern IA into northern IL and
...Southern and central Plains...
Influx of richer low-level moisture beneath steep lapse rates
associated with a warm elevated mixed layer should result in strong
instability (2500-3000 J/kg MLCAPE) in the southern and central
Plains warm sector. Strong diabatic warming and dryline mixing
should eventually erode the cap, and storms are expected to initiate
from northwest TX into the TX Panhandle and eventually move east
into western OK during the evening. Despite weak vertical shear
(25-30 kt, 0-6km) The thermodynamic environment appears very
favorable for wet downbursts and large hail before activity weakens
later in the evening.
...Central Rockies region...
Storms should once again initiate in upslope flow regime where winds
aloft and vertical shear along southeast periphery of upper low will
be sufficient for a few rotating updrafts. MUCAPE from 500-800 J/kg
and 50+ kt effective shear will support a threat for supercells
capable of large hail. In addition, steep lapse rates and large
temperature-dewpoint spreads will promote a threat for downburst
winds. At this time, marginal instability could be a limiting factor
for a more robust severe threat, but an upgrade to slight risk might
be warranted in later updates.
...Central Appalachians to Middle Atlantic region...
Backdoor front has shunted warm sector south of the stronger winds
aloft. Most storms (modulated by vorticity maxima embedded within
the west-northwest flow regime) will remain confined to north of the
quasi-stationary front. However any storms developing near this
boundary may become capable of producing a few strong to damaging
wind gusts as the boundary layer destabilizes during the afternoon
and early evening.
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