ACUS01 KWNS 272001
SWODY1
SPC AC 272000

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0200 PM CST Tue Feb 27 2024

Valid 272000Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
NORTHEAST IL AND FAR NORTHWEST IN THIS EVENING...AND ACROSS PORTIONS
OF THE LOWER AND MIDDLE OH VALLEY THIS EVENING THROUGH TONIGHT....

...SUMMARY...
Severe thunderstorms, associated with large hail, damaging gusts,
and tornadoes, some of which may be significant, will be possible
from late this afternoon into the overnight, across portions of
northeast Illinois and northwest Indiana as well as the Lower and
Middle Ohio Valley.

...20Z Update...

...Northern IL/Southern WI This Evening...
Recent surface analysis places a low near the IA/MO/IL border
intersection. A dryline arcs southeast from this low to near STL and
then back southwest into north-central AR. Dewpoints behind this
dryline are in the 40s, while dewpoints across much of IL are in the
upper 50s/low 60s. A warm front also arcs northeastward from this
low to just north of the ORD, then eastward across southern Lake
Michigan, and southeastward across northern IN into far west-central
OH.

General expectation outlined in the previous discussion remains
valid, with convective initiation anticipated near this low, with
the resulting storms then tracking northeastward in the vicinity of
the warm front. It remains uncertain whether or not these storms
will be on the warm side of the boundary. Given the kinematic
fields, any surface-based storms would likely be supercellular and
capable of all severe hazards, including tornadoes. Recent guidance
include the 18Z and 19Z WoFS as well as the 12Z MPAS runs all
suggest an increasing likelihood for surface-based, warm sector
storms. Given these trends, expanded the Enhanced southeastward to
include more of northeast IL and far northwest IN and also
introduced a 10% significant tornado probability.

...OH Valley This Evening and Overnight...
Overall expectation outlined in the previous outlook remains
unchanged for tonight across the OH Valley. As the night
progresses, activity will likely evolve into fast-moving bowing
structures with an enhanced risk of damaging wind gusts and a few
tornadoes. Given the strengthening low-level flow, destructive wind
gusts around 75 mph are possible, with a strong tornado or two
possible as well.

..Mosier.. 02/27/2024

.PREV DISCUSSION... /ISSUED 1026 AM CST Tue Feb 27 2024/

...OH Valley...
A fast-moving southern-stream shortwave trough over the central
Plains will track eastward today and begin affecting parts of MO by
late afternoon or early evening. Most 12z guidance suggests that at
least isolated thunderstorm development will begin around/after dusk
as the large-scale forcing overspreads the northern extent of
moist/unstable air mass from southwest MO into southern IL. These
storms will intensify and track eastward overnight roughly along the
OH river, moving into parts of OH/WV/PA by early morning Wednesday.
Initial storms may be discrete, with sufficient vertical shear for
supercells structures capable of all severe hazards. As the night
progresses, activity will likely evolve into fast-moving bowing
structures with an enhanced risk of damaging wind gusts and a few
tornadoes. A strong tornado or two cannot be ruled out. Have added
an ENH risk area for this scenario overnight.

...IL/WI...
A compact surface low is forecast to deepen across eastern IA this
afternoon, with a narrow warm sector pulling northward into much of
northern IL. Strong forcing near the low and along the associated
warm front will lead to intense thunderstorms across portions of
northern IL after 22z. Forecast soundings show steep low and mid
level lapse rates and sufficient CAPE, along with strong low and
deep layer shear profiles. This will be conducive to supercell
structures capable of very large hail and damaging winds. There
remains uncertainty whether these storms will be in the warm-sector,
or will be undercut by nearby cold air. Have upgraded a small part
of this area to ENH risk for hail, but there is also concern for
tornadoes if the activity remains surface-based.

$$
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ACUS01 KWNS 111253
SWODY1
SPC AC 111252

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0752 AM CDT Thu Apr 11 2024

Valid 111300Z - 121200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR EASTERN
OHIO AND NORTHWEST WEST VIRGINIA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR FAR SOUTHERN
GEORGIA INTO NORTH AND CENTRAL PARTS OF FLORIDA...

...SUMMARY...
Severe thunderstorms with a few tornadoes, scattered damaging winds,
and isolated large hail are possible across the upper Ohio River
Valley and parts of the Appalachians this afternoon. Scattered
damaging winds and a couple of tornadoes are possible in far
southern Georgia into central Florida, mainly this morning through
early afternoon.

...Synopsis...
Water-vapor imagery this morning shows a potent mid-level low/trough
centered near the AR/MS/TN border with an upstream trough over the
Upper Midwest forecast to phase with the Southeast trough. A
cyclone near the TN/MS border will deepen as it develops
north-northeast into the Lower Great Lakes by early evening. A
trailing surface cold front will push east across portions of the Southeast/southern Appalachians during the day, before clearing the
Southeast coast by early Friday morning.

...Upper OH River Valley...
Considerable uncertainty remains for this forecast in terms of the
magnitude of destabilization across the OH Valley late this morning
through the afternoon. This uncertainty is primarily due to low
cloud cover and weak capping resulting in scattered
showers/low-topped thunderstorm activity and the potential to remain
relatively cool in the boundary layer. However, mid-level dry air
evident in water-vapor imagery is wrapping through the base of the
mid-level low/trough over TN, and this mid-level dry intrusion
forecast to spread northeast into portions of the Upper OH Valley.
Weak instability coupled with some enlargement of the hodograph can
support an environment in which discrete cells and semi-discrete
clusters evolve into supercells. A few tornadoes are possible if
stronger updrafts/supercells manage to develop, in addition to an
accompanying threat for damaging gusts and perhaps marginally severe
hail.

...Florida/Georgia...
Ongoing pre-frontal broken band of strong to severe thunderstorms
over north FL and the eastern Gulf of Mexico will gradually shift
east across the northern half of the Peninsula through the morning
and into the afternoon. The northern rim of rich low-level moisture
(upper 60s to lower 70s deg F surface dewpoints) have advected into
north FL early this morning. Although lapse rates will remain
modest, it appears the richer moisture will contribute to adequate surface-based buoyancy (500-1250 J/kg MLCAPE) across the northern
half of the Peninsula today. The Jacksonville and Tampa 88D VAD
wind profiles are quite strong this morning and will likely remain
so through the early afternoon as the larger-scale mid-level trough
pivots eastward over the FL Peninsula by early evening. The risk
for a couple of tornadoes and damaging gusts will likely maximize
through the midday before the thunderstorm band moves offshore and
forcing for ascent gradually abates by late afternoon as the
synoptic low lifts well to the north.

...Mid-Atlantic states into Carolinas...
A less focused and more conditional severe risk seems evident for
the Carolinas later this afternoon and northward into the
Mid-Atlantic states this evening as the upper trough encroaches on
the general region. A broad warm-air advection regime north of the
FL/GA early-day MCS will slowly destabilize today, aided in part by
lower 60 deg F dewpoints north, mid to upper 60s south. Long
hodographs will favor storm organization with any robust updrafts.
Isolated to widely scattered strong to severe storms capable of a
threat for damaging gusts and a couple of tornadoes are possible,
mainly over parts of western VA, with lower coverage expected
farther east over the coastal plain/Delmarva.

..Smith/Mosier.. 04/11/2024

$$
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ACUS01 KWNS 141248
SWODY1
SPC AC 141246

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0746 AM CDT Sun Apr 14 2024

Valid 141300Z - 151200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN OHIO INTO PENNSYLVANIA...

...SUMMARY...
Severe thunderstorms should develop late this afternoon in a narrow
corridor across the upper Ohio Valley into Pennsylvania and
vicinity. Damaging winds should be the main threat. Severe hail and
perhaps a couple of tornadoes also appear possible as this activity
spreads slowly southward into this evening.

...Ohio Valley into the Mid-Atlantic and Northeast...
Early morning surface observations show a dearth of low-level
moisture from the upper OH Valley into the Mid-Atlantic, with
surface dewpoints generally in the 30s. However, boundary-layer
moisture will gradually increase through the day across these
regions, as a weak surface low migrates eastward from the Great
Lakes across NY. By late afternoon, generally upper 40s to low 50s
surface dewpoints should become focused in a narrow corridor along
and south of front from OH into PA and southern NY. With upper
troughing persisting over eastern Canada and parts of the Northeast,
generally westerly mid-level winds across the Midwest/OH Valley will
aid in the eastward advection of an EML and associated steep
mid-level lapse rates. Even though low-level moisture is expected to
remain limited, these steepened lapse rates aloft, along with
diurnal heating, should encourage the development of weak to locally
moderate MLCAPE late this afternoon.

Surface-based thunderstorm initiation across this region will likely
be delayed until 20-21Z or later, as lingering MLCIN and a cap
gradually erodes. Initial development should be focused along the
front across parts of eastern OH into western/central PA, with
additional development eventually occurring into eastern PA and
parts of southern NY. Given strong deep-layer shear and favorable
lapse rates, large hail may occur with the more robust cores
initially. Some threat for a couple of tornadoes may also exist with semi-discrete convection, as sufficient low-level shear will be
present for updraft rotation. But, with the surface front aligned
mostly parallel to the enhanced westerly low/mid-level flow, upscale
growth into small bowing clusters should quickly occur as convection
spreads south-southeastward. Scattered damaging winds will likely
become the main threat with these clusters through the early evening
in a narrow spatial corridor extending from eastern OH into PA where instability and steep low/mid-level lapse rates should be maximized.
The damaging wind threat will gradually decrease through the evening
as instability lessens with southward/eastward extent.

..Gleason/Grams.. 04/14/2024

$$
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ACUS01 KWNS 161244
SWODY1
SPC AC 161242

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 AM CDT Tue Apr 16 2024

Valid 161300Z - 171200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF IOWA...NORTHERN MISSOURI...AND NORTHWESTERN ILLINOIS...

...SUMMARY...
Scattered severe thunderstorms appear likely today, centered mostly
over northern Missouri, Iowa, and northwestern Illinois. Large hail,
damaging winds, and tornadoes should occur in this corridor. More
isolated activity could develop as far south as the Ozarks of
northern Arkansas.

...Synopsis...
An upper trough/low over the central Plains this morning will
continue to eject east-northeastward across the mid MO Valley and
Upper Midwest through tonight. A 70-90 kt mid-level jet will
overspread parts of the Midwest through the day, contributing to
substantial deep-layer shear and thunderstorm organization. At the
surface, a 990 mb low over central NE will likewise develop
east-northeastward through the day in tandem with the upper wave. A
warm front should lift northward across parts of the Midwest, with
generally low to mid 60s surface dewpoints present across the warm
sector as far south as the Ozarks. A composite Pacific cold
front/dryline will move quickly eastward from the southern/central
Plains into the mid Ms Valley by this evening. This boundary should
stall across the southern Plains, and may begin to lift northward
late tonight.

...Midwest/Mid Mississippi Valley...
A large area of showers and thunderstorms is ongoing this morning
from parts of eastern KS/NE/SD into IA. Much of this activity across
the central Plains is being driven by large-scale ascent associated
with the ejecting upper trough/low, along with strong warm/moist
advection with a 40-50 kt southerly low-level jet. As this
convection continues to spread eastward this morning in tandem with
the migrating low-level jet axis, it will probably become more
elevated, especially as it moves into northern MO and IA and a less
unstable airmass to the north of the warm front. Still, an isolated
severe threat may persist in the short term with these
thunderstorms. The effect of this early-day convection on robust destabilization in its wake along/ahead of the cold front remains a
concern and potentially limiting factor for additional severe
thunderstorm development this afternoon. Even so, most guidance,
including multiple recent runs of the RAP, shows a narrow corridor
of weak to moderate instability developing along/south of the warm
front in IA, and ahead of the cold front sweeping eastward across
MO/IA. This re-destabilization should be aided by a pocket of steep
mid-level lapse rates and cold temperatures aloft on the southeast
side of the upper trough/low.

Assuming that low to mid 60s surface dewpoints and modest daytime
heating can aid in this instability actually materializing, then a
risk for supercells should exist over parts of IA, northern MO, and northwestern IL. Both low-level and deep-layer shear appear strong
enough for supercells. Steep lapse rates will aid in hail
production, with some chance for 2+ inch diameter stones with the
more robust cores. Tornadoes will also be a concern, as the enhanced boundary-layer flow and enlarged/curved hodographs associated with a
the low-level jet will aid in updraft rotation. The best tornado
potential will probably be focused along/near the warm front in IA,
where the greatest low-level shear is forecast. Here, a strong
tornado appears possible. Isolated to scattered damaging winds may
also occur.

Farther south into the Ozarks and Mid-South, the potential for
severe thunderstorms appears more conditional. Various NAM/RAP
forecast soundings exhibit generally poor lapse rates, with at least
weak inhibition through much of the period. Given these regions
displacement from the upper trough/low to the north, it remains
unclear how robust updrafts will be in a more marginal low/mid-level
lapse rate environment. Still, have maintained the Slight Risk into
parts of the lower MS Valley, but convection may struggle to
intensify this afternoon/evening.

..Gleason/Grams.. 04/16/2024

$$
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ACUS01 KWNS 301250
SWODY1
SPC AC 301248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Tue Apr 30 2024

Valid 301300Z - 011200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
AND WESTERN IOWA TO NORTHEASTERN KANSAS...

...SUMMARY...
The greatest threat for severe weather (large hail severe gusts and
a few tornadoes possible) is from western and central Iowa to
northeastern Kansas.

...Synopsis...
A fairly low-amplitude, nearly zonal pattern will remain across the
CONUS east of the Rockies, and downstream from a slow-moving mid/
upper-level cyclone now over the northern Rockies. By the end of
the period, this cyclone (containing numerous mesoscale vorticity lobes/shortwaves) should pivot to the northern High Plains, roughly
astride the northern border of MT and ND with the Canadian Prairie
Provinces.

The most impactful associated feature will be a shortwave trough
evident in moisture-channel imagery over portions of eastern MT into central/southern WY. This perturbation should shift eastward to
near a BIS-MHE-LNK axis by 00Z, then eject northeastward over the
upper Mississippi Valley tonight. Meanwhile, in response to height
falls and synoptic trough amplification over the Intermountain West,
south of the cyclone, flow over the central and southern Rockies and
adjoining Plains should back gradually to southwesterly, but with
few, if any, notable embedded perturbations today.

At the surface, 11Z analysis showed a low over northwestern SD, with occluded/cold front arching across western SD, western NE and
northern CO. The low should move eastward to northeastern SD by
00Z, with a triple point over northern IA or extreme southern MN,
warm front to northern IL, and cold front to northeastern and
south-central KS, the OK Panhandle, and Raton Mesa. That low should
move over southern MN and northern WI through tonight, possibly
reaching western Upper MI by 12Z, while the cold front reaches
northeastern IL, the central/western Ozarks, and northern OK,
stalling near a lee-side/frontal-wave low in the CAO/DHT area by
12Z. As moisture return continues, a dryline will become better
defined today from central KS to the TX Permian Basin, shifting
eastward to east-central KS, north-central/southwestern OK,
northwest TX, and northernmost Coahuila before stalling late this
afternoon.

...Lower Missouri Valley and vicinity...
Widely scattered to scattered thunderstorms are forecast to form
this afternoon--earliest around the Siouxland area and later with
southward extent. All forms of severe are possible, but with an
earlier lean to the greatest hail vs. greatest wind threats.
Activity should coalesce from mid-late afternoon onward and shift
eastward over the outlook area, weakening this evening into tonight.

Observed thermodynamic profiles and forecast soundings from this
area southward toward the Gulf Coast reasonably show a shallow moist
layer in low levels, easily mixed via diurnal heating. This appears legitimate, related to trajectories emanating from an extensive
area of outflow observed over the northwestern Gulf and adjoining
parts of east TX, LA and AR to the lower Mississippi Valley. That
outflow came from MCS activity yesterday. Nonetheless, diurnal
heating should help to steepen low/middle-level lapse rates
considerably and eliminate MLCINH -- by early afternoon over
northwestern parts of the outlook area (where moisture will be lower
but deep-layer lift/cooling aloft greater), and mid/late afternoon
roughly south of I-80 (stronger heating/moisture, adequate lift).

Strengthening and veering of winds with height will yield enlarged
hodographs and favorable deep-shear profiles for supercells, albeit
with somewhat high LCL atop a deep mixed subcloud layer. Forecast
soundings reasonably depict MLCAPE ranging from around 500-1000 J/kg
in the SUX/FSD area to over 3000 J/kg down the narrow plume of
favorable instability in eastern KS. Effective-shear magnitudes of
50-65 kt and SRH of 200-400 J/kg are expected. This parameter space
and profile will support severe wind and hail, both in early
supercell stages (when large to locally very large hail also is
expected), and as upscale aggregation of convection occurs with
small-scale cold pools.

...Southern Plains...
Isolated to locally scattered thunderstorms, including a few
supercells, are possible for a few hours this afternoon into early
evening, initiating near the dryline and moving slowly east-
southeastward (right movers) to faster northeastward (left movers).
Large hail and severe gusts will be the main concerns, and a
conditional significant (2+ inch diameter) hail risk may occur with
any sustained supercell in this corridor. However, in the absence
of large-scale support, specific foci along the dryline appear
unclear, with coverage uncertain (and probably low) over most of the
area. This makes predictability low for any specific mesobeta-scale
patch where greater unconditional probabilities may develop.

Strong surface heating along the dryline will support at least
isolated thunderstorm development mid/late this afternoon, in an
environment of modest low/middle-level flow but strong veering with
height. Before dark, SRH will be small in the lowest couple km,
however, with effective shear magnitudes in the 30-40-kt range,
supporting a blend of organized multicell and transient/isolated
supercell potential. Steep lapse rates, dewpoints commonly in the
60s F, and enough heating for a deep/well-mixed subcloud layer,
should support MLCAPE of 2000-3500 J/kg. Activity should weaken
considerably after dark.

...NY...
Widely scattered thunderstorms are possible today in a zone of
large-scale ascent preceding the trough aloft, superimposed on
modest low-level convergence related to low-level trough drifting
eastward over the area. The trough may manifest at the surface as a
weak low, but projected inflow-layer parcels should remain largely
(if not entirely) elevated above the boundary layer, where moisture
will be greatest and MUCINH weakest. Elevated MUCAPE of 500-1200
J/kg is possible, and briefly surface-based parcels may be
attainable in pockets of sustained heating over portions of the
Finger Lakes to Catskills vicinities. The best-organized cells may
produce small hail and subsevere gusts. Lack of greater near-
surface instability (magnitude and area), and weak midlevel lapse
rates, preclude a severe threat warranting an unconditional outlook
at this time.

..Edwards/Leitman.. 04/30/2024

$$
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