LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 AM CDT Tue Aug 08 2023
Valid 081300Z - 091200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHEAST
CO...SOUTHWEST NE...FAR NORTHWEST KS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY ACROSS
PARTS OF THE SOUTHEAST...
...SUMMARY...
Scattered severe thunderstorms are expected across parts of the
central High Plains during the late afternoon into tonight. Large to
very large hail, severe gusts, and a tornado or two will be the
potential hazards. Scattered damaging winds and isolated severe hail
will also be possible through around sunset across parts of the
Southeast.
...Central High/Great Plains...
A shortwave trough over southeast ID will progress into the central
High Plains by tonight. As this occurs, modest lee troughing will
support south-southeasterly low-level winds, which should allow for
air mass recovery in the wake of yesterday's MCS amid a stout
elevated mixed layer. This low-level flow regime beneath 35-45 kt
mid-level zonal flow will yield an elongated, nearly-straight
hodograph. This will overlap a confined corridor of MLCAPE from
2500-3000 J/kg centered on the northeast CO/southwest NE border.
Initial high-based thunderstorm development will occur off the
higher terrain of southeast WY and north-central CO by mid-afternoon
and spread east, impinging on the larger buoyancy environment. A few
splitting supercells are expected with a north/south-oriented
cluster likely evolving relatively quickly as outflows consolidate
towards the CO/NE/KS border area. The potential for a longer-track
discrete supercell appears greatest along the southern periphery of
convective development owing to lack of interference from other
supercells and closer proximity to the upper jet centered on
southern CO/KS. Very large hail, significant severe wind gusts, and
a tornado or two are all possible.
Uncertainty is greater with the overall degree of severe threat
tonight. Convective coverage will indubitably increase as a
nocturnal low-level jet strengthens northward from the southern High
Plains and large-scale ascent waxes ahead of the aforementioned
shortwave trough. Given pronounced MLCIN expected across much of
western KS at peak heating, prospects for a severe-producing MCS
initially appear questionable. It seems plausible that convection
may tend to regenerate across northeast CO to the NE/KS border area
during the evening before finally growing upscale overnight as
additional elevated convection develops east-southeast. As such, a
long-duration threat for sporadic large hail and isolated severe
wind gusts may be sustained in/near the cat 3/ENH risk area, with
lower confidence in the spatial extent of these threats towards
central parts of NE/KS.
...Southeast...
An MCS is ongoing from the Ark-La-Miss back into far eastern OK and
generally appears to have remained sub-severe over the past few
hours. The primary short-term uncertainty is exactly when this MCS
will turn the corner today and begin to accelerate east-southeast
with a damaging wind threat. See MCD 1905 for further discussion
regarding the threat this morning.
In the wake of yesterday's severe MCS, a pronounced buoyancy
gradient is roughly oriented from west to east across central
portions of MS/AL/GA. Amid modest west-southwesterly low-level flow
this gradient will move slowly through the day but intensify as
buoyancy becomes large across south AL/GA and north FL. The current
MCS or remnants of it will likely progress along this buoyancy
gradient while attempting to develop southward into it from midday
through the afternoon. While the large-scale outflow from this
activity will likely outpace the stronger mid-level flow to its
northwest, there will remain adequate deep-layer shear for organized
multicell clustering with scattered damaging winds as the primary
hazard.
...New England...
A shortwave trough from southern QC to the Lower Great Lakes will
slowly move east across the St. Lawrence Valley and New England
through tonight. The low-level warm conveyor region ahead of this
trough will largely become divorced from surface-based buoyancy by
midday. Until that occurs, a low probability/brief tornado threat
remains possible where low 70s surface dew points are present across
southern New England. More probable convective development this
afternoon is anticipated over western New England where deep-layer
shear will be weak in closer proximity to the trough axis and
potential for organized severe thunderstorm development is low.
...Northern MN and eastern ND...
A shortwave trough digging across MB and northwest ON will aid in a
cold front pushing south-southeast across northern MN and trailing
into ND. An adequate combination of deep-layer shear and instability
should support a marginal and isolated severe wind/hail threat
during the late afternoon to early evening.
..Grams/Dean.. 08/08/2023
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