SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Fri Aug 04 2023
Valid 042000Z - 051200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WITHIN THE
NORTHEAST...NORTHERN/CENTRAL MISSOURI...PORTIONS OF THE CENTRAL
PLAINS...
...SUMMARY...
Scattered severe thunderstorms remain possible across parts of the
Northeast, Missouri, and the central into the southern High Plains
later today through early tonight.
...20Z Update...
Minor changes were made to the wind probabilities within the
Mid-South/Southeast to account for observations and stabilization
behind ongoing convection. The remainder of the outlook is
unchanged.
..Wendt.. 08/04/2023
.PREV DISCUSSION... /ISSUED 1134 AM CDT Fri Aug 04 2023/
...Synopsis...
A broad mid-level trough continues to slowly progress across the
Northeast as an upper ridge remains in place across the southern
CONUS, with multiple mid-level perturbations cresting the upper
ridge over the Central Plains. Though some cloud cover and
showers/thunderstorms persist across the Northeast, adequate
clearing through the remainder of the morning should efficiently
heat the boundary layer beneath cooler mid-level temperatures and
stronger flow aloft to promote strong to potentially severe
thunderstorms through the afternoon. Meanwhile, residual clouds,
showers, and thunderstorms should clear across the MO Valley into
the Southeast today, with surface heating contributing to adequate
buoyancy to support strong to potentially severe thunderstorms.
These storms should initiate with the passage of the aforementioned
mid-level impulses cresting the upper ridge. Lastly, upslope
low-level flow will support the development of strong to potentially
severe thunderstorms across the central into the southern High
Plains later this afternoon and evening.
...Northeast...
Scattered to potentially widespread thunderstorms are expected to
initiate across the Hudson Valley late this morning into early
afternoon ahead of a surface lee trough as surface heating continues
across the Northeast. 16Z mesoanalysis shows modest (i.e. 6-6.5
C/km) mid-level lapse rates overspreading the Hudson Valley.
Nonetheless, -14 to -15 C 500 mb temperatures and 70+ kts of 300 mb
flow (in association with an approaching upper-level jet streak)
will promote adequate instability (given mid 60s F surface
dewpoints) and deep-layer shear to support a severe threat this
afternoon. Multicells and transient supercell structures are
expected, with large hail and damaging gusts the main concerns. By
late afternoon, storms should congeal into one or more clusters. If
this occurs, then damaging gusts will become the primary threat.
...MO Valley into the Southeast...
Ongoing clouds and precipitation should gradually clear through the
afternoon to support increasing buoyancy (perhaps over 3000 J/kg
MLCAPE) as 7+ C/km mid-level lapse rates overspreads 70+ F surface
dewpoints. The approach of an MCV from the remains of an earlier MCS
will support convective initiation later this afternoon around and
just east of the KC Metropolitan area. Elongated and curved
hodographs (especially in the low-levels) will encourage multicell
and supercell structures initially. While damaging gusts are the
main threat, locally backed low-level winds ahead of the MCV track
may encourage a localized tornado threat for a few hours. However,
storms should merge into one or more MCSs later this afternoon, with
severe gusts the primary concern.
Across the southeast, thunderstorm clusters should develop along the
eastern periphery of the upper ridge. Given rich low-level moisture
and strong buoyancy (with the 16Z mesoanalysis already showing up to
5000 J/kg SBCAPE in place), water-loaded downdrafts may accompany
the stronger storm cores, and at least isolated damaging gusts are
possible later this afternoon.
...Central into the Southern High Plains...
Upslope flow induced by a surface lee trough, along with diurnal
heating, will support the development of at least isolated to
potentially scattered thunderstorms late this afternoon, from
western SD to the TX Panhandle. A plume of 7-8 C/km mid-level lapse
rates will advect over the central High Plains in tandem with the
ejection of a subtle 700 mb impulse. 2000+ J/kg MLCAPE and an
increase in deep-layer shear will result, with modestly lengthening
hodographs (and 40 kts of effective bulk shear) expected. Multicells
and supercells are expected to be the initial storm modes, with both
severe hail wind the primary threats. By evening though, weak
low-level shear should encourage outflow and subsequent cold pool
mergers, with severe gusts then becoming the dominant severe threat.
A few outflow-dominant thunderstorms may also develop along the
surface trough across portions of the southern High Plains by
afternoon peak heating. These storms will develop atop a dry, mixed
boundary layer, with a couple of severe gusts possible.
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