SPC Apr 24, 2024 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1238 AM CDT Wed Apr 24 2024

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
WEST TEXAS THIS EVENING...

...SUMMARY...
Strong to severe thunderstorms will be possible today across parts
of Oklahoma and west Texas. Large hail and severe gusts will be the
primary hazards.

...Synopsis...

An upper ridge over the Rockies will shift east into the Plains
through tonight. However, guidance suggests subtle shortwave
impulses will migrate through the ridge during the late afternoon
into the evening/overnight. At the surface, strengthening lee
troughing is forecast across eastern NM near the TX border.
Meanwhile, a stationary boundary is forecast to extend across the TX
South Plains vicinity into southern/central OK, while a dryline
extends southward along the NM/TX border into southwest TX. Several
forecast models suggest a bulge in the dryline is possible across
far west TX where a weak surface low may develop. Overnight, the
stationary boundary is expected to lift northward as a warm front,
becoming located across the TX Panhandle into northern OK.

Further east, an upper trough will move across the Northeast states.
Boundary-layer moisture will remain limited, though midlevel
moisture will be plentiful. Cool temperatures aloft and modest
westerly flow will support isolated to scattered thunderstorms ahead
of an eastward-progressing cold front.

...OK - This Morning...

Thunderstorms are expected to develop early this morning across
central OK north of the stationary boundary in a warm advection
regime along the north edge of returning low-level moisture. This
activity is expected to be elevated. However, steep midlevel lapse
rates and increasing westerly mid/upper flow should be sufficient
for organized cells. Large hail will be possible with storms that
develop. However, coverage remains in question given expected height
rises through the morning hours as the upper ridge slowly shifts
east.

...West TX toward SW OK - This evening...

Capping will preclude convection for most of the day. However,
low-level moisture will increase with northwest extent on
southeasterly low-level flow, and low 60s F dewpoints are expected
into the Permian Basin and South Plains vicinity. Steep midlevel
lapse rates atop this moistening boundary-layer will foster moderate
instability from 1500-2500 J/kg. By late afternoon/early evening,
convection should begin to develop as inhibition weakens due to
increasing moisture and some indication of a weak impulse ejecting
east across the southern Rockies. Veering low-level wind profiles
become west/southwesterly aloft will result in favorable shear
profiles supporting supercells. Large hail to 2 inches in diameter
and gusts to 70 mph will be possible with storms that develop.

...Northern OK - Late Tonight...

As the stationary boundary lifts northward as a warm front
overnight, another round of warm advection thunderstorms will be
possible, this time from the eastern TX Panhandle into northern OK.
Forecast guidance varies considerably regarding coverage and
location of potential development, though the overall environment
(moderate elevated instability and modest shear) conditionally will
support hail.

...Northeast...

While boundary-layer moisture will remain poor today, cold
temperatures aloft will support weak instability. Deep-layer
westerly flow around 20-30 kt may support transient organized
cells/clusters by early afternoon. Meanwhile, heating ahead of the
cold front will allow for steepening low-level lapse rates. Gusty
winds to 40 mph will be possible with afternoon thunderstorms, but
overall severe potential appears too low for severe probabilities.

..Leitman/Weinman.. 04/24/2024


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SPC Apr 23, 2024 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1213 AM CDT Tue Apr 23 2024

Valid 231200Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHWEST TEXAS...

...SUMMARY...
A few severe thunderstorms capable of producing large hail (2+ inch
diameter) and gusts to 65 mph will be possible this afternoon and
evening across northwest Texas. Additional strong storms producing
hail to near 1 inch diameter and 60 mph gusts are possible from
southeast Wisconsin and northern Illinois into Lower Michigan.

...Synopsis...

An upper shortwave trough will pivot eastward across the Upper Great
Lakes to the Northeast today. Meanwhile, upper ridging will be
focused over the Rockies. At the surface, an area of elongated low
pressure is forecast from Quebec to the Upper MS Valley. A secondary
surface low is forecast to develop over the TX Panhandle/South
Plains. A cold front will link between these two areas of low
pressure, extending from southwest WI to central OK and the TX
Panhandle by early/mid afternoon. A prior cold frontal intrusion
into the Gulf of Mexico and surface high pressure over the Southeast
will limit boundary-layer moisture. However, east/southeasterly
low-level trajectories into TX become more south/southwest into OK
and the along the surface trough into the Upper Great Lakes will
allow for low 60s F dewpoints south (southern Plains) to 40s F
dewpoints north (Great Lakes).

...Upper Great Lakes...

Stronger large-scale ascent will be focused across WI/Lower MI and
vicinity during the afternoon ahead of the surface front and upper
shortwave trough. While boundary-layer moisture will remain modest,
temperatures aloft are forecast to be quite cool, resulting in very
steep midlevel lapse rates. This will foster MLCAPE values generally
less than 750 J/kg amid modest effective shear magnitudes greater
than 30 kt. This should support isolated strong to severe storms
during the afternoon/evening from southeast WI into northern IL/IN
and parts of Lower MI. Elongated hodographs and mainly elevated
instability coupled with the cold temperatures aloft may support
hail to near 1 inch diameter. Steep low-level lapse rates amid a dry
boundary-layer also may support locally strong gusts.

...Northwest TX/Southwest OK vicinity...

Large-scale ascent will be somewhat nebulous over the region today,
but subtle northwest flow aloft amid veering low-level wind profiles
will result in 40+ kt effective shear magnitudes. Strong heating in
the vicinity of a surface low/triple point and dryline, coupled with
steep midlevel lapse rates, will aid in moderate destabilization
(MLCAPE around 1500-2000 J/kg possible). This should support a few
organized cells during the late afternoon/evening. Elongated
forecast hodographs and modest vertical shear through 3 km suggests
supercells capable of large hail (2+ inch diameter) are possible.
Weak low-level flow and mixing to around 850 mb also indicates some
potential for locally strong/severe gusts. While storm coverage is
expected to remain isolated, given potential for significant hail
(2+ inch diameter), a Slight (level 2 of 5) risk has been included.

..Leitman/Weinman.. 04/23/2024


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SPC Apr 22, 2024 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1152 PM CDT Sun Apr 21 2024

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHEAST FLORIDA PENINSULA...

...SUMMARY...
Strong to locally severe thunderstorms, capable of marginally severe
wind gusts and hail, will be possible across the southeast Florida
Peninsula this afternoon.

...South Florida...

An upper trough oriented from the Carolinas to the Southeast will
shift east over the Atlantic waters by 00z. A belt of enhanced
mid/upper westerly flow associated with the trough will overspread
much of FL.

At the surface, a cold front located over central FL will shift
south through late afternoon. Ahead of the front, a moist airmass is
already in place, with surface dewpoints in the upper 60s F.
Modestly steep midlevel lapse rates atop this moist boundary-layer,
coupled with daytime heating, will foster MLCAPE values to around
1000-1500 J/kg. The greatest instability will be focused near the
southeast FL coast. Low-level flow will remain light and mainly
parallel to the surface front, limiting convergence. Still,
inhibition is forecast to be weak and thunderstorms are expected by
afternoon near the surface front. Elongated hodographs, and around
35 kt effective shear magnitudes suggest supercells are possible.
However, given weak forcing and possible strong outflows given steep
low-level lapse rates beneath 850 mb, clustering may also be
possible. Strongest convection will likely be confined to near the
southeast FL coast. Locally strong/damaging gusts and perhaps
marginally severe hail possible through late afternoon.

...Central Plains...

An upper shortwave trough will migrate across the northern Plains,
with height falls extending into the central Plains this
afternoon/evening. A dearth of boundary-layer moisture is forecast
in the wake of a cold frontal intrusion deep into the Gulf of Mexico
and a large area of surface high pressure extending from the
southern Plains to the Mid-South/TN Valley. Nevertheless, modest
midlevel moisture is forecast over the region amid a plume of steep
mid and low-level lapse rates. Minor elevated instability (generally
750 J/kg MUCAPE or less) is evident in forecast soundings above a
warm layer around 700 mb. Some weak convection is expected and a few
strong gusts or small hail is possible across southern NE into
northern KS. However, longevity of stronger updrafts appears limited
and coverage of convection is expected to be low, precluding
marginal severe probabilities at this time.

..Leitman/Weinman.. 04/22/2024


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SPC Apr 21, 2024 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 PM CDT Sun Apr 21 2024

Valid 212000Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHEAST
GEORGIA INTO NORTHERN FLORIDA...

...SUMMARY...
Isolated damaging gusts and marginally severe hail remain possible
for a few hours this afternoon/evening across southeast Georgia and
north Florida.

...Southeast Georgia and northern Florida...
Within the past few hours, a transient supercell on the northern
fringe of the effective warm sector along the SC coast produced a
measured severe (58 mph) wind gust, indicating that the environment
across northern FL into southeast GA remains conducive for severe
storms. However, convection has struggled to maintain intensity over
the past few hours despite steadily diminishing MLCIN - possibly
owing to a temporal displacement between the initial storms and the
more favorable thermodynamic environment that is currently becoming
established. Renewed attempts at convective initiation along the
cold front are noted across south-central GA, so a severe wind/hail
risk should persist for the next several hours (see forthcoming MCD
#504 for details). Latest CAM guidance suggests this potential will
be maximized between 21-00 UTC across southeast GA into far northern
FL before the front moves off the GA coast and nocturnal cooling
begins to hinder surface-based convection further south into the FL
peninsula.

..Moore.. 04/21/2024

.PREV DISCUSSION... /ISSUED 1124 AM CDT Sun Apr 21 2024/

...North FL/south GA this afternoon/evening...
Visible satellite imagery late this morning shows a cumulus field
and a destabilizing airmass to the east of an ongoing band of
convection near a southwest-northeast oriented front. Ample heating
over the area to the east of patchy cirrus will promote temperatures
warming into the lower 80s deg F. 12z model guidance so far has a
negative bias on surface dewpoints across north FL compared to
observations (3-6 deg F too dry). This is partially explained by a
richer moist profile observed through almost 850 mb via the 12z
Tallahassee raob. As a result, slightly higher dewpoints (upper 60s
deg F) and greater buoyancy (1000-1500 J/kg MLCAPE) are expected
than previously forecast. Water-vapor imagery shows a lead
disturbance moving east across the central Gulf Coast, and it will
reach the northeast Gulf by late this afternoon/early evening.
Ascent and some strengthening in flow will aid in some storm
organization (reference 50-kt 2-6 km flow at Tallahassee on the 88D
VAD). Limited low-level convergence and a warm layer near 800 mb
may act to hinder an otherwise more organized potential severe
setup. Regardless, isolated 50-65 mph gusts and marginally severe
hail are possible with the stronger storms this afternoon into the
early evening.


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