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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Saturday, June 29, 2024

SPC Jun 29, 2024 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CDT Sat Jun 29 2024

Valid 291630Z - 301200Z


Damaging thunderstorm gusts and a few tornadoes appear possible
today over parts of the Lower Great Lakes to upper Ohio Valley and
Mid-Atlantic. Severe gusts may also be focused this afternoon and
evening over the Ozarks vicinity, and the Raton Mesa and adjacent
south-central High Plains.

...Lower Great Lakes and Upper Ohio Valley into the Mid-Atlantic...
A loosely organized band of convection is ongoing across parts of
northern/central OH. As an upper trough over the Great Lakes and
eastern Canada continues to move eastward through the period,
current expectations are for convection to gradually increase in
coverage and intensity this afternoon across eastern OH into western
PA. Recent visible satellite imagery shows substantial cloudiness
across this area, which should hinder diurnal heating to some
extent. Still, even modest heating of the rather moist low-level
airmass should support at least weak instability by late this
afternoon. Low-level and deep-layer shear appear sufficiently strong
for a mix of multicells and supercells. Damaging winds will be a
concern with any bowing cluster that can form and spread eastward
across parts of the Mid-Atlantic through the afternoon/evening. A
couple of tornadoes may also occur with any sustained supercell or
embedded QLCS circulations. See Mesoscale Discussion 1472 for more
details on the short-term severe threat across OH into northern WV
and western PA.

There also appears to be some chance for additional convection to
develop along the cold front across IL/IN this afternoon, perhaps
associated with a remnant MCV over eastern MO. Substantial
cloudiness is present across much of this region ahead of the front.
But, any thunderstorms that can form may be capable of producing
isolated hail and/or strong to damaging winds. Considered including
this area in a Slight Risk, but confidence remains low in robust
convection persisting with eastward extent into the OH Valley in the
wake of earlier thunderstorm activity.

A Slight Risk for damaging winds has been introduced for southern
MO, northeast OK, and vicinity. Outflow from earlier convection,
along with the slowly sagging cold front, should continue southward
across these areas through late afternoon while also providing a
focus for additional convection. Moderate to strong instability is
forecast to develop this afternoon in a narrow zone along/ahead of
the front. While deep-layer shear should remain fairly modest, most
12Z guidance shows a greater concentration of robust convection
developing across southern MO and vicinity late this afternoon and
early evening. Loosely organized clusters capable of producing
mainly damaging winds should spread generally east-southeastward
through the evening. Isolated hail may also occur.

...Southern/Central High Plains...
No changes have been made to the Slight Risk across the
southern/central High Plains. Scattered thunderstorms are expected
to develop during the late afternoon and evening in a weak
post-frontal, upslope flow regime. Generally upper 50s to low 60s
surface dewpoints and steep mid-level lapse rates will support a
narrow corridor of moderate instability by late afternoon. While
mid-level flow is expected to remain weak, vertically veering wind
profiles with height through mid/upper levels will support
sufficient deep shear for transient, slow-moving supercells and
loosely organized clusters developing off the higher terrain of
southern CO and northern NM. Occasional severe gusts appear possible
with this activity as low-level lapse rates become steepened through
diurnal heating. Some hail may also occur with the strongest cores.

Despite veered low-level winds ahead of the cold front and weak
mid-level lapse rates, boundary-layer heating should yield a plume
of weak instability, with MLCAPE around 500-1000 J/kg by this
afternoon. Strong speed shear will support hodograph elongation.
This may yield a supercell or two capable of isolated severe hail
and locally strong wind gusts in the eastern U.P. into Lower MI.
But, overall coverage of strong/severe thunderstorms is expected to
remain rather limited across this area.

..Gleason/Thornton.. 06/29/2024

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