SPC AC 150600
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Thu May 15 2025
Valid 151200Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN MINNESOTA...WISCONSIN...NORTHEAST ILLINOIS...NORTHERN
INDIANA...SOUTHWEST AND SOUTHERN MICHIGAN...AND FAR NORTHWEST
OHIO...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID TO UPPER MISSISSIPPI VALLEY...GREAT LAKES...OHIO VALLEY AND
MID-ATLANTIC...
...SUMMARY...
Severe thunderstorms are expected across parts of the upper
Mississippi River Valley and Great Lakes this afternoon and evening.
Hailstones greater than 2 inches will be possible, along with
tornadoes with a few that could be strong. Scattered wind damage
will be likely, with wind gusts over 75 mph over parts of Lower
Michigan and northern Indiana. Isolated severe thunderstorms are
also expected through the lower Ohio River Valley, Ozarks and in
parts of the Mid-Atlantic.
...Mid to Upper Mississippi Valley/Great Lakes/Ohio Valley...
A negatively-tilted mid-level trough will move northeastward into
the Upper Midwest today, as an associated jet streak translates
eastward into the Ozarks. A secondary jet streak will move
northeastward into the mid Missouri Valley. Strong large-scale
ascent will overspread a broad moist sector from the Great Lakes
into the Ohio Valley, resulting in a widespread severe weather event
today.
At the surface, a low will consolidate and move northward across the
eastern Dakotas. A well defined warm front will advance northward
into the Wisconsin, as a cold front moves eastward into the mid to
upper Mississippi Valley. Ahead of the front, surface dewpoints from
the mid 60s to the lower 70s F will result in moderate instability
over much of the moist sector. Thunderstorms are first expected to
initiate near the mid-level low over the upper Mississippi Valley,
with storms developing south-southeastward along and ahead of the
front during the afternoon.
Indications suggest that the storms will remain somewhat spaced out,
at least early in the event. The discrete nature of the convection,
combined with moderate deep-layer shear, will be favorable for
supercell development. A broken line of severe storms is expected to
move east-northeastward into the vicinities of Milwaukee and Chicago
late this afternoon. RAP forecast soundings at 21Z along the western
shore of Lake Michigan have MLCAPE near 2000 J/kg, with 0-6 km shear
of 35 to 40 knots, and 700-500 mb lapse rates near 7.5 C/km. This
will be favorable for large hail and wind damage associated with
supercells. The more intense supercells may produce hailstones
greater than 2 inches in diameter. In addition, 0-3 km
storm-relative helicity in the 250 to 300 m2/s2 will also support
tornadoes, with the threat becoming maximized as supercells mature.
A few strong tornadoes appear likely.
Severe threat coverage will likely be maintained as a broken line
segment gradually organizes. A transition to linear mode appears
likely by early evening. Supercells and rotating elements within the
line should be capable of producing tornadoes. Wind damage will also
be likely along the leading edge of the line, with gusts over 75 mph
possible from western Lower Michigan southward into northern
Indiana. A potential for hailstones greater than 2 inches in
diameter will continue during the early evening with supercells
embedded within the line.
Further south into the lower Ohio Valley, storm coverage will be a
bit more isolated. However, cells that can develop within the
strongly unstable airmass will likely become supercells with large
hail and severe gusts. A tornado threat is also expected. It appears
that a corridor of greater severe threat will develop somewhere near
the Ohio River during the late afternoon, which could be dependent
upon the distribution and magnitude of instability.
...Ozarks/Ark-La-Tex...
Southwest mid-level flow will be in place today across the Ozarks
and Ark-La-Tex, as a jet streak moves eastward into the region. A
moist airmass will be in place to the southeast of the jet, where
surface dewpoints will be in the upper 60s and lower 70s F. By
afternoon, much of this airmass will be moderately unstable.
However, large-scale ascent to the south of the jet is forecast to
remain relatively weak, which should keep convective development
isolated. Any cell that can initiate despite a capping inversion
could become severe and have a large hail and wind-damage threat.
The threat could persist from late afternoon into the early evening.
....Central Appalachians/Mid-Atlantic...
A mid-level ridge will move eastward into the central Appalachians
today, as northwesterly flow remains to the east of the Appalachian
crest. At the surface, a moist airmass will be in place along much
of the southern and central Atlantic Seaboard. Surface dewpoints in
the 60s F will likely result in moderate instability by afternoon.
Although large-scale ascent will be weak, topographic forcing and
increasing low-level convergence could aid convective initiation as
surface temperatures warm up. Short-term model solutions suggest the
greatest convective potential will be across eastern Virginia, where
low-level flow is forecast to increase during the day. This,
combined with moderate deep-layer shear and steep low-level lapse
rates, may be enough for an isolated severe threat. Severe wind
gusts and large hail will be possible with supercells or short
intense line segments.
..Broyles/Lyons.. 05/15/2025
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
SPC AC 150529
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 AM CDT Thu May 15 2025
Valid 161200Z - 171200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FRIDAY
AFTERNOON INTO FRIDAY NIGHT ACROSS PARTS OF NORTHEASTERN
ARKANSAS...EAST CENTRAL AND SOUTHEASTERN MISSOURI...SOUTHERN
ILLINOIS...SOUTHERN INDIANA...SOUTHWESTERN OHIO...MUCH OF WESTERN
AND CENTRAL KY...WESTERN AND MIDDLE TENNESSEE...
...SUMMARY...
Severe thunderstorms appear likely to develop across parts of the
middle Mississippi through lower and middle Ohio Valleys Friday
afternoon into Friday night. During the late afternoon into
evening, this may include a few intense supercells posing a risk for
large hail and tornadoes. During the evening into the overnight
hours, this probably will include an upscale growing and organizing
cluster posing a risk for strong, damaging winds and perhaps a
continuing risk for tornadoes.
...Discussion...
Downstream of a prominent mid-level high over the southern mid- to
subtropical latitudes of the eastern Pacific, split flow will
persist across much of North America through this period. Within
this regime an initially deep and occluded surface cyclone, centered
over northern Minnesota at the outset of the period, is forecast to
weaken Friday through Friday night, as it migrates into the Upper
Great Lakes region in response to a short wave perturbation pivoting
around the southern periphery of the mid-level circulation center.
It appears that this perturbation will come in phase with another
short wave perturbation forecast to accelerate east-northeast of the
central Great Plains through much of the Ohio Valley by early
Saturday. Another vigorous short wave trough digging around the
northeastern periphery of the Pacific ridge may reach the northern
California coast by the end of the period, preceded by at least one
more modest perturbation migrating northeastward across the northern
Baja vicinity.
In lower levels, associated with the occluding cyclone, a
weak/weakening Pacific cold front/dry line appears likely to stall
across the lower Great Lakes through Ohio River vicinity, and across
the Ark-La-Tex into Rio Grande River by 12Z Friday. This may be
trailed by another weak front across the Upper Midwest through the
central Great Plains and Texas South Plains, which is forecast to be
overtaken by the primary cold front surging southeastward from the
upper Mississippi Valley/northern Great Plains. By late Friday
night, this cold front may reach the lower Ohio Valley and central
Great Plains.
Preceding the consolidating fronts, low-level moisture return and
moderate to strong destabilization is forecast across the middle
Mississippi and lower Ohio Valleys on strengthening south to
southwesterly flow. The potential northern extent of the moisture
return remains unclear, based on model output, and this could be
impacted by outflow associated with possible early period convective
development across the lower Ohio Valley into portions of the
Allegheny and Cumberland Plateaus. Depending on how these
uncertainties play out, it might not be out of the question that a
more substantive outbreak of severe thunderstorms could evolve than
currently depicted. It is possible areal coverage and probabilities
could be increased further in later outlooks for this period.
...Lower Great Lakes into northern Mid Atlantic...
Uncertainty lingers concerning the potential for severe weather.
However, the intersection of the initial weak surface cold
front/dryline and warm front could still be providing a focus for
strong to severe thunderstorm development at the outset of the
period across the lower Great Lakes/upper Ohio Valley vicinity.
Aided by continuing inflow from better potential instability across
the Ohio Valley, in the presence of moderate to strong vertical
shear, it is possible that this could continue into the day Friday,
perhaps evolving into an organizing cluster which should tend to
propagate southeastward and perhaps pose potential for strong to
severe surface gusts.
...Middle Mississippi into Ohio Valley...
There remains at least some signal that a modest short wave
perturbation, within the belt of westerlies emanating from the
subtropical eastern Pacific, may be contributing to vigorous
convective development at the outset of the period, or shortly
thereafter, across parts of the lower Ohio Valley. If this occurs,
it might not be out of the question that the boundary-layer
downstream, into the western slopes of the Appalachians, might
destabilize in time to support an upscale growing cluster with
potential to produce to produce severe wind and hail.
The impact of this possible early period convection might be the
primary contributor to at least some continuing model disparity
concerning upstream boundary-layer moistening and destabilization
(particularly the northern extent) across the middle Mississippi
into lower Ohio Valleys. However, it still appears most probable
that destabilization, as far north as the I-44 corridor of
central/eastern Missouri, will support the initiation of storms by
early afternoon, in response to forcing for ascent associated with
the mid-level perturbation emerging from the central Great Plains.
This is generally forecast to shift east-northeastward into the
lower Ohio Valley through late Friday afternoon, in an environment
that may support at least a window of opportunity for
sustained/long-lived supercells with potential to produce large to
giant hail and a couple of strong tornadoes. Into Friday evening
and overnight, there remains a considerable signal in model output
that large-scale forcing for ascent will support a notable upscale
growing and organizing cluster, in the presence of seasonably strong
(and increasingly convectively augmented) westerly deep-layer mean
flow. This may support widespread severe surface gusts,
occasionally in excess of 65 kt, across a swath from southern
Indiana/western Kentucky and northern Tennessee toward the Allegheny
and Cumberland Plateaus.
..Kerr.. 05/15/2025
WUUS02 PTSDY2
SPC AC 141932
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 PM CDT Wed May 14 2025
Valid 161200Z - 171200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST
MISSOURI...SOUTHERN ILLINOIS/INDIANA...SOUTHWEST OHIO...AND PORTIONS
OF WESTERN TO NORTHERN KENTUCKY...
...SUMMARY...
Severe thunderstorms are expected across the Middle Mississippi and
Ohio Valley region Friday afternoon and evening. All-severe hazards
are possible with this activity. More isolated severe thunderstorms
will extend southwestward into northeast Texas, and northeast into
the Mid-Atlantic.
...Mid-South/Ohio Valley vicinity...
An upper trough over the southern High Plains will pivot quickly
east/northeast across the Midwest on Friday. As this occurs, strong
mid/upper southwesterly flow will overspread the region, with a 500
mb jet around 70-90 kt forecast. At the surface, A very moist
airmass will be in place from southern MO into southern IL and
northeast into OH. Increasing southerly low-level flow ahead of a
surface cold front will allow a warm front, roughly along the I-70
corridor at mid-morning, to lift north toward the northern IL/IN/OH
through the afternoon. Cooling aloft will result in steep midlevel
lapse rates atop the mid/upper 60s F dewpoint surface warm sector,
resulting in strong destabilization.
A low-level jet around 45-65 kt is forecast to overspread the region
from peak heating into the evening, coincident with increasing
large-scale ascent. Both the eastward-advancing cold front/dryline
across MO, and the warm front vicinity will be a focus for
convective initiation. One or more bowing clusters is possible, in
addition to more discrete supercells. Given vertically veering
supercells wind profiles, significant severe storms appear possible
-- with a risk for all hazards accompanying this activity, including
very large hail, tornadoes, and intense wind gusts. The southward
extent of highest severe potential is a bit uncertain given
orientation of surface boundaries and potential overnight convection
in the Day 2/Thursday time period impacting parts of the KY
vicinity.
Eventually, a northeast to southwest line of storms will likely
congeal during the late evening/nighttime hours and sag southward
across KY into the TN Valley, with a gradually lessening severe risk
with southward extent during the overnight hours.
...TX into OK/AR...
With southwest extent, severe potential is a bit more
uncertain/conditional. Some minor height rises may occur across TX
and the into AR during the late afternoon/evening. Large-scale
ascent will be weaker and any capping may be more difficult to
overcome. Nevertheless, a very moist and unstable airmass will be in
place amid supercell wind profiles. If storms can develop, very
large hail and strong gusts will be possible.
...Mid-Atlantic Vicinity...
Convection may be ongoing in a warm advection regime Friday morning
as a weak shortwave impulse moves across the region through
afternoon. Moderate mid/upper flow will support effective shear
magnitudes around 25-35 kt, and be sufficient for some organized
convection. Pockets of stronger heating downstream from morning
activity will allow for weak to moderate destabilization. Isolated
strong to severe storms producing hail and gusty winds will be
possible.
..Leitman.. 05/14/2025
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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