RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Fri Mar 31 05:53:01 UTC 2023.
No Mesoscale Discussions are in effect as of Fri Mar 31 05:53:01 UTC 2023.
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Fri Mar 31 2023
Valid 311200Z - 011200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE MID MISSISSIPPI VALLEY/MIDWEST AND LOWER MISSISSIPPI
VALLEY...
...SUMMARY...
Intense and widespread severe thunderstorms are expected this
afternoon into the overnight hours across portions of the Middle
Mississippi Valley and Mid-South vicinity, eastward to the Lower
Ohio and Tennessee Valleys. Intense, damaging gusts and several
tornadoes (some strong and long-track) are expected.
...Discussion...
Strong, dynamic upper low will begin to deepen early in the period
as it tracks across the central Plains into the Midwest Friday
evening. This feature will encourage a pronounced surface low to
eject into southeast NE by sunrise Friday, then into lower MI by the
end of the period. Significant moisture return ahead of the
associated cold front will lead to an air mass supportive of severe
thunderstorms from the mid MS Valley/Midwest into the lower MS
Valley.
...Mid-MS Valley/Midwest Vicinity...
Early this morning, a strong upper trough is shifting across western
WY/Four Corners region. An upper low should evolve over the central
Plains by late morning with further deepening expected as the low
tracks into the mid MO Valley by early evening. Latest model
guidance suggests a 500mb speed max will increase to near 110kt as
it translates across MO into the OH Valley during the latter half of
the period. As a result, intense 12hr height falls, on the order of
270-300m, will spread across the mid MS Valley/Midwest which should
encourage the aforementioned surface low to deepen as it matures
over northeast IA/southwest WI.
Strong low-level warm advection is currently aiding a corridor of
elevated convection from northeast NE across northern IA,
along/north of a stationary front draped across this region. Latest
thinking is much of the warm sector should remain convective-free
through late morning until leading edge of stronger forcing spreads
east in conjunction with rapid boundary-layer heating ahead of the
cold front. Steep low-level lapse rate plume should develop across
the central Plains early then spread/develop east-northeast across
MO into portions of IA ahead of the front. Forecast soundings
suggest convective temperatures will be breached by 18z immediately
ahead of the low/front. Scattered supercells should develop quickly
thereafter, tracking quickly northeast in response to the
fast-moving upper trough/speed max. Discrete supercells should be
the initial storm mode with very large hail expected. With time,
strong forcing may lead to line segment and clusters. Strong shear
will support long-lived updrafts. In addition to very large hail,
tornadoes can be expected (a few strong) with these storms,
especially prior to any line segment evolution.
While the more concentrated storms should be noted across
IA/northern MO into northwest IL, there is concern for more isolated
long-track supercells across central MO into IL. All hazards can be
expected with these storms.
...Lower MS Valley...
A secondary corridor of concentrated convection is expected to
evolve ahead of the front across the lower MS Valley. Early-day
mid-level speed max that races across northern OK into MO will allow
the front to surge into southern MO, arcing across the Arklatex by
late afternoon. Surface dew points have risen into the mid 60s
across northeast TX/western LA early this morning. This air mass
will easily advance across AR into western KY prior to convective
initiation. As a result, SBCAPE should be on the order of 2000 J/kg
with very strong sfc-6km shear and low-level SRH. Any supercells
that evolve within this air mass will do so within an environment
that favors long-lived updrafts and strong tornadoes. Upscale growth
into a QLCS is expected during the latter half of the period. Severe
threat should spread east across the northern Gulf States Friday
night.
..Darrow/Thornton.. 03/31/2023
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1226 AM CDT Fri Mar 31 2023
Valid 011200Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY ACROSS
PARTS OF EASTERN OHIO...MUCH OF PENNSYLVANIA...SOUTHERN INTO CENTRAL
NEW YORK STATE AND PARTS OF NORTHWESTERN NEW JERSEY...
...SUMMARY...
Strong thunderstorms may develop and organize east of the lower
Great Lakes into the Hudson Valley and northern Mid Atlantic region
Saturday, accompanied by a risk for severe wind gusts.
...Synopsis...
While another significant short wave trough begins to dig within the
main branch of mid-latitude westerlies, near/offshore of the Pacific
Northwest coast, downstream flow is forecast to become less
amplified into and through a confluent regime to the east of the
Canadian Prairies and U.S. Great Plains during this period. To the
south of a lingering vortex of Arctic origins (initially centered
over southern Hudson Bay), models suggest that a vigorous short wave
perturbation will dig to the southeast of James Bay and come in
phase with an initially more substantive perturbation within this
regime. The consolidating mid-level troughing may shift across New
England into the Canadian Maritimes by 12Z Sunday.
Associated forcing for ascent is forecast to support strong
secondary surface cyclogenesis across the St. Lawrence Valley
vicinity, while an initial occluded low over lower Michigan weakens.
A conglomerating trailing cold front appears likely to advance east
of the Appalachians and offshore of much of the Atlantic Seaboard
into the Gulf coast vicinity by the end of the period.
A narrowing pre-frontal plume of higher precipitable water content
may advect across much of New England and Mid Atlantic coastal areas
by mid afternoon, and the southern Atlantic coast later in the day.
Within this regime, weak lapse rates and/or lingering convective
cloud cover and precipitation may limit appreciable destabilization
Saturday, particularly to the north of the southern Atlantic
Seaboard.
Strongest mid-level cooling and height falls are forecast to
overspread the upper Ohio Valley/lower Great Lakes region through
the northern Mid Atlantic and western New England by early Saturday
evening. This may provide the focus for the primary severe weather
potential for this period.
...Lower Great Lakes into Hudson Valley/northern Mid Atlantic...
Lower/mid-tropospheric subsidence/warming likely will be in the
process of overspreading the upper Ohio Valley and lower Great Lakes
region at 12Z Saturday, before nosing east-northeastward through the
day. This is expected to allow for appreciable surface heating and
boundary-layer mixing to contribute to low-level destabilization
prior to the arrival of the mid-level forcing for ascent and
cooling, which is expected to provide support for low-topped
thunderstorm development. This may impact areas to the east and
south of Lakes Erie and Ontario Saturday morning into midday, with
convection possibly consolidating into an organizing convective
system. Given the shear and the strength of the mean flow (40-50+
kt in the lowest 6 km), coupled with the steepening low-level lapse
rates, activity may support severe wind gusts while spreading
east-northeastward across southern New York and Pennsylvania through
the afternoon, perhaps as far east as the Hudson Valley vicinity by
early Saturday evening. Farther east, in areas not impacted by the
cool Atlantic marine layer, a gradually waning risk for strong wind
gusts may continue into the evening hours.
...South Atlantic Seaboard...
Strong deep-layer mean flow and shear will be at least conditionally
supportive of organized severe weather potential on Saturday, given
sufficient destabilization. At least widely scattered strong to
severe thunderstorm development still appears possible. It remains
unclear whether instability and mid/upper support will become
sufficient for anything more widespread, but higher severe
probabilities could still become more apparent and introduced in
later outlooks for this period.
..Kerr.. 03/31/2023
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