SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Tue Jul 30 2024
Valid 302000Z - 311200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE MID MO
VALLEY SOUTHEASTWARD INTO THE MID MS VALLEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
DAKOTAS...
...SUMMARY...
Severe thunderstorms are expected this afternoon through tonight
across a broad area from eastern Nebraska and Iowa into parts of the
Midwest, Tennessee Valley and southern Appalachians, with multiple
swaths of damaging winds likely within this corridor. Severe
thunderstorms are also possible across parts of the northern Plains.
...20Z Update...
...TN Valley into the southern Appalachians...
Organized convective line continues to progress southeastward across
central KY, with more disorganized, multicellular convection
downstream across middle and eastern TN. The convective line will
likely continue southeastward for at least the next several hours.
Ample low-level moisture and buoyancy exists downstream, but
deep-layer vertical shear decreases with southern extent as well.
This weakening shear may result in a trend towards a more
disorganized character, with the outflow eventually outpacing the
deep updrafts. However, this may not occur until later this evening,
with damaging gusts possible along the line until this weakening
occurs.
...Mid MS Valley this afternoon and evening...
As mentioned in recently issued MCD #1746, some re-intensification
on the southern flank of the decaying convective cluster has been
noted across west-central IL over the past 30 minutes or so.
Additional convection has developed near the intersection of outflow
boundaries across northern MO. Ample low-level moisture exists
downstream across east-central MO into southern IL with dewpoints in
the mid/upper 70s F. Strong buoyancy exists in this area as well,
with recent mesoanalysis estimating MLCAPE over 3000 J/kg. This
suggests the developing storms across central MO could intensify,
with additional new development likely across central and southern
MO. There is also some chance that additional development occurs
along the outflow extending from central MO into west-central IL.
All of these scenarios suggest that the threat for severe
thunderstorms continues across the region, with damaging gusts as
the primary risk. Some isolated large hail is also possible with the
initial, more cellular storms.
...Central Plains/Mid MO Valley into the Mid MS Valley overnight and
early Wednesday...
Evening thunderstorm development still appears probable from central
NE into the Mid MO Valley as a subtle, low-amplitude shortwave
trough interacts with the very moist, unstable, and uncapped airmass
over the region. Large to very large hail is possible with the
initial development, with a trend towards an organized line
thereafter. Given the continued severe potential, no changes are
needed to the severe probabilities over the region.
...Northern/Central Plains...
Thunderstorm development is anticipated in the next 1-2 hours across
the western Dakotas. Storms are expected to intensify
as they migrate east into central North and South Dakota. High cloud
bases and steep low-level lapse rates will support strong
downbursts.
..Mosier.. 07/30/2024
.PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Jul 30 2024/
...Mid Missouri Valley into the Midwest/Ohio Valley/Southeast...
A larger than usual amount of uncertainty remains regarding
convective evolution this afternoon though tonight. Ongoing cluster
in southern IA will move southeastward across the mid MS Valley into
a rapidly destabilizing airmass with enhanced northwesterly winds at
mid/upper-levels supporting sufficient deep-layer shear for
continued updraft organization. A swath of severe/damaging winds
appears likely with this cluster given the favorable parameter
space. Therefore, the Enhanced Risk for damaging winds has been
extended southeastward to account for the forecast evolution of this
MCS. Another ongoing cluster over the lower OH Valley should also
pose some threat for severe/damaging winds as it and associated
outflow on its southwest flank spreads east-southeastward across KY
and perhaps parts of TN the rest of this afternoon/evening.
Additional robust thunderstorm development appears possible through
the period in a broad corridor from central/eastern NE through the
lower OH Valley and Southeast, with swaths of damaging winds likely
the main threat. Details on where/when this activity will develop
remain rather uncertain. But, isolated supercells may develop across
central/eastern NE late this afternoon/evening in the vicinity of a
surface low/lee trough. Very large hail may occur with this
convection, with a greater threat for severe/damaging winds possible
if this activity can grow upscale into another cluster and spread
southeastward across the mid MO and mid MS Valleys this
evening/overnight.
...Northern Plains...
Weak mid-level height falls amid moderate to strong instability
should foster to widely scattered thunderstorm development along a
surface trough/dryline across parts of the Dakotas this afternoon.
Moderate mid-level westerlies should support deep-layer shear around
30-35 kt, sufficient for a few organized storms, including a few
supercells, capable of both large hail and damaging gusts this
afternoon and evening.
...Mid-Atlantic Vicinity...
A weak mid/upper-level trough and will move across the
Mid-Atlantic and vicinity through this evening. Scattered
thunderstorm development should continue this afternoon from VA into
parts of PA. While there is some uncertainty regarding the extent of
heating and destabilization due to lingering cloudiness, a couple of
stronger cells/clusters may become capable of producing isolated
damaging winds.
...Northeast...
Weak to locally moderate instability may develop this afternoon from
parts of northern New York into northern New England. While storm
coverage remains uncertain, deep-layer shear and relatively cool
temperatures aloft could support a couple of modestly organized
thunderstorms capable of locally damaging winds, and possibly some
hail.
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