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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