SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0246 PM CDT Fri Jun 14 2024
Valid 142000Z - 151200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF
CO/KS/NE AND THE UPPER OH VALLEY TO NEW ENGLAND...
...SUMMARY...
Scattered severe thunderstorms with large hail and wind gusts around
60-80 mph will be possible through this evening along the Front
Range to the central Great Plains. Scattered strong to locally
severe storms with sporadic damaging winds and isolated hail will
also be possible across parts of the Northeast and Mid-Atlantic
through about dusk.
...20Z Update...
Convection from New England to the Upper OH Valley has largely
struggled to greatly intensify beyond a marginally severe status as
of yet. Still, where boundary-layer warming has been more pronounced
from parts of the Upper OH Valley, DE Valley, and southern to
eastern New England, a few clusters may yet produce strong to
localized severe gust before convection diminishes after dusk.
The central states severe threat appears on-track. Deepening
convection from the Sangre de Cristo Mountains northward along the
Front Range should intensify as it impinges on the strengthening
buoyancy plume over the central High Plains. For additional
short-term information, see MCD 1262.
..Grams.. 06/14/2024
.PREV DISCUSSION... /ISSUED 1128 AM CDT Fri Jun 14 2024/
...Central Plains...
A mid-level shortwave trough over the Southwest will continue
northeastward today towards the central Rockies/Plains.
Post-frontal, low-level easterly upslope flow is ongoing across the
central High Plains to the Front Range in eastern CO. A somewhat
moist-level airmass is present across this area, and robust daytime
heating is forecast with little cloud cover present on recent
visible satellite imagery. Initially high-based thunderstorms should
form over the central Rockies as forcing aloft overspreads this
region. Modest, but sufficient, mid-level flow attendant to the
shortwave trough and related deep-layer shear should support some
updraft organization and a threat for severe hail with more discrete
cells initially.
A fairly quick evolution/upscale growth into a loosely organized
cluster still appears likely as convection spreads
east-northeastward into the central High Plains later this afternoon
and early evening. An increasing threat for severe/damaging winds
around 60-70 mph should materialize as this mode transition occurs.
As low-level lapse rates become steepened with robust heating, and
the boundary layer becomes very well mixed, some risk for isolated
significant severe gusts (75-80 mph) may develop. This risk appears
relatively greatest across parts of eastern CO into adjacent
portions of western KS/NE. Late this evening, the cluster should
eventually encounter a less unstable airmass with eastward extent
across the central Plains, and subsequently weaken.
...Northern Plains/Rockies...
Diurnal destabilization should occur today near/east of a weak
surface low across the northern High Plains, with modest instability
extending westward across parts of the northern Rockies. Isolated to
widely scattered thunderstorms should form by late afternoon into
the evening, with sufficient deep-layer shear to support isolated
stronger storms capable of producing occasional hail and
strong-to-severe wind gusts. This threat should tend to remain
fairly isolated/marginal.
...Northeast/Mid-Atlantic...
Recent visible satellite imagery shows cloud cover remains prevalent
across parts of the Northeast and Mid-Atlantic ahead of a cold
front. This should tend to delay/mute daytime heating to some
extent, especially with northward extent into New England. Even so,
filtered diurnal heating, and less cloud cover southward into the
Mid-Atlantic, will support modest destabilization. Most guidance
continues to suggest that MLCAPE will generally reach around
500-1000 J/kg by mid afternoon ahead of the front. Current
expectations are for thunderstorms to gradually increase in coverage
and intensity across these areas this afternoon as the front
continues eastward in tandem with a mid/upper-level trough over
eastern Canada. With around 30-40 kt of deep-layer shear available
to support updraft organization, occasional damaging winds should be
the primary threat with any clusters or short line segments that can
develop. Isolated hail may also occur with initially more discrete
activity. This activity is forecast to spread eastward through the
afternoon and early evening, before eventually weakening and/or
reaching the coast.
Additional convection may form this afternoon along the trailing
portion of the cold front in western PA, northern WV, and
southeast/central OH. An embedded, low-amplitude mid-level shortwave
trough over the Great Lakes/Upper Midwest may aid this development,
along with modest low-level convergence along the front. Overall
thunderstorm coverage is still somewhat uncertain with westward
extent into the OH Valley. But, isolated to widely scattered
thunderstorms, including a mix of a couple of supercells and small
clusters with associated hail/wind threat, support a westward
expansion of the Slight Risk to account for this potential.
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