Convective Outlook

SPC 1300Z Day 1 Outlook
Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0757 AM CDT Sun Jun 23 2024

Valid 231300Z - 241200Z



Scattered damaging winds and a few tornadoes are likely across parts
of the Northeast and New England, with additional severe storms
expected across the Ohio Valley, Mid-Atlantic region, as well as the
Northern High Plains.

...Northeast/New England...
Negligible Outlook changes are warranted, with an active
severe-weather day still expected regionally. Rich boundary-layer
moisture (dewpoints in the upper 60s to low 70s F) will advect
northward, and in the wake of morning convection, filtered solar
heating will allow for moderate destabilization over much of New
England. Most guidance shows 1500-2000 J/kg of MLCAPE developing by
early to mid afternoon despite only modest low and mid-level lapse
rates. More than sufficient for strong updrafts, scattered storm
development is expected first near the warm front and subsequently
along the trailing surface trough. Strong deep-layer shear of 45-60
kt will support both supercells and short line segments. With a
favorable parameter space for organized storms, damaging winds, some
hail and a few tornadoes are all expected.

A corridor of locally greater severe risk remains apparent across
portions of southern Maine, VT, NH and west-central Massachusetts.
this is were forecast soundings show large curved hodographs with
ESRH of 250-350 m2/s2 and STP values of 1.5-3. With the potential
for a mix of supercells and line segments, the risk for tornadoes
will exist. Eventual upscale growth into a linear cluster may also
support a locally greater risk of damaging winds toward the coast
later this evening. Additional storms are possible as the cold front
moves through later this evening, though multiple rounds of prior
convection may limit the severity of any subsequent convection later
this evening.

...Mid-Atlantic States...
More isolated storm coverage is expected with southward extent.
Displaced from the main lobe of ascent from the passing shortwave
trough, convection may take longer to organize owing to the warmer
mid-level temperatures and weaker synoptic forcing. Still,
deep-layer shear and buoyancy are favorable for organized multicell
clusters and a few supercells. Damaging winds, and occasional hail
are the most likely threats, though a tornado could occur with any
sustained supercell.

...Upper Ohio Valley/Tennessee Valley...
Ahead of the trailing cold front, scattered thunderstorm development
is expected during the afternoon. Rich boundary-layer moisture will
support a broad plume of moderate instability. Several bands of
thunderstorms should track east southeast along the southern
periphery of the enhanced flow aloft. Sufficient for some storm
organization, 20-30 kt of effective shear should support a few
clusters capable of damaging gusts and isolated hail.

...Northern Plains including eastern Montana to North Dakota...
Accompanying the wave over southern Canada and the Northwest, a
deepening surface cyclone with a cold front trailing southward into
Montana will serve as a focus for isolated storm development this
afternoon and evening, with the highest probability for storms
closer to the international border where a Slight Risk has been
introduced. Low-level southeasterly flow will transport a confined
plume of modest low-level moisture into parts of east Montana,
resulting in a corridor of MLCAPE from 500-1500 J/kg. Deep-layer
shear will be favorable for organized convection capable of isolated
damaging winds and hail.

...Central High Plains...
Very warm temperatures are expected along a lee trough across the
central Plains this afternoon. With temperatures near 100 F,
scattered high-based thunderstorms are expected over parts of
eastern Colorado, southwest/south-central Nebraska and western
Kansas. Deep inverted-v profiles will support a risk for severe
gusts with strong downdrafts. Located on the southern periphery of
the stronger upper-level flow, these storms may persist through
early evening before weakening.

..Guyer/Mosier.. 06/23/2024

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Updated 23 June 2024 | 8:01 am