RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 PM CDT Sat Oct 18 2025
Valid 182000Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT
FROM THE ARK-LA-TEX TO THE LOWER OHIO AND MISSISSIPPI VALLEYS...
...SUMMARY...
Scattered severe thunderstorms are possible mainly this afternoon
into tonight across parts of the Ark-La-Tex, Ozarks, mid to lower
Mississippi and lower Ohio Valleys. Damaging winds, a few tornadoes
and hail may occur.
...20Z Update...
Given the progression of the shortwave trough in the southern
Plains, severe probabilities have been removed behind ongoing
convection from parts of northeast Texas into western Arkansas and
southwest Missouri. The 18Z soundings from Shreveport and Little
Rock show modest mid-level lapse rates and low-level shear. The wind
profile is expected to improve somewhat later this afternoon into
the early evening. Discrete showers and thunderstorms are steadily
increasing in intensity in the ArkLaTex region. As this activity
move north and east over the next several hours, it will pose a
locally higher tornado threat so long as storm mode remains
favorable. Additional forecast details can be found in the previous
forecast below. Other short-term details are in MCD 2152.
..Wendt.. 10/18/2025
.PREV DISCUSSION... /ISSUED 1117 AM CDT Sat Oct 18 2025/
...Synopsis...
A southern stream shortwave trough will eject quickly
east-northeastward from TX/OK to AR/MO, prior to phasing with an
amplifying northern stream trough by tonight across the mid MS
Valley. Downstream from the phasing troughs, a deepening surface
cyclone will develop northeastward tonight from the mid MS Valley to
Lower MI, as a trailing cold front surges southeastward from the
Plains into the mid-lower MS Valley.
...TX/OK today into the MS/OH Valleys through early Sunday...
Regional 12z soundings revealed a plume of 7.5-8 C/km midlevel lapse
rates (FWD-OUN-LMN) atop low-level dewpoints in the 60s, which is
already contributing to moderate buoyancy (MUCAPE up to 1500 J/kg)
as of mid morning. As continued forcing for ascent with the lead
shortwave trough overspreads the moisture/buoyancy plume, ongoing
thunderstorms are expected to increase in coverage through the
afternoon from southern MO/IL to eastern OK/western AR and
north/northeast TX. Initial storms will be in the form of
clusters/short line segments with upscale growth into a more
extensive squall line expected by later this afternoon/evening.
Buoyancy will increase some in the moisture plume through the
afternoon with surface heating in cloud breaks, and deep-layer
vertical shear will increase with the approach of the ejecting
midlevel trough. Thus, the stronger embedded cells will have the
potential to produce large hail (1-1.75 inches in diameter) along
with an increase in the threat for wind damage as convection becomes
more linear. The tornado threat is a bit more uncertain given the
early/messy start to convection this morning, and since low-level
shear will not be strong this afternoon in the warm sector as a
result of primary cyclogenesis not occurring until tonight from IL
into lower MI (north of the richer low-level moisture). Still, a
couple of tornadoes may occur with embedded circulations. There
will be the potential for more discrete supercells and a few
tornadoes ahead of the larger-scale line of storms from far east TX
into LA/southern AR and MS overnight where boundary-layer dewpoints
exceed 70 F and low-level shear increases.
Though buoyancy will be weak, rapidly strengthening wind fields
overnight and forcing for ascent along the synoptic cold front could
support a low-topped line of convection with the potential for wind
damage and possible a couple of embedded tornadoes from the OH
Valley into southeast Lower MI ~06-12z.
Read more
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1212 PM CDT Sat Oct 18 2025
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
APPALACHIANS TO THE MID-ATLANTIC...AND ACROSS PARTS OF THE GULF
COAST...
...SUMMARY...
Isolated wind damage may occur on Sunday into early Monday from
parts of the central Appalachians to the Mid Atlantic coastal
regions. Additional isolated severe storms are possible over the
Gulf Coast early Sunday.
...Synopsis...
An upper trough over the MS Valley will shift east/northeast on
Sunday, overspreading much of the Midwest and TN Valley, and
becoming oriented from western NY to the Mid-Atlantic coast by
Monday morning. Strong flow aloft, with an 80-100 kt 500 mb jet
streak will overspread portions of the central Appalachians to the
Mid-Atlantic coast. Around 40-50 kt 850 mb south/southwesterly flow
also is expected to spread east from the Gulf Coast and Ohio Valley
to the Atlantic coast through the period.
At the surface, the primary cyclone over Lower MI will lift
northeast into Ontario and Quebec, with a trailing surface trough
and cold front extending southward to the central Gulf Coast. The
front will develop east/southeast, and move offshore the Atlantic
coast by the end of the period, with the southern extent of the
front arcing southwestward into the northern FL Peninsula. Richer
boundary layer moisture will remain confined to the Gulf
Coast/Southeast states though peak heating, with some greater
northward moisture transport into the Mid-Atlantic coast after 00z.
...Central Appalachians to Mid-Atlantic...
Boundary layer moisture will remain limited, with dewpoints
generally only reaching into the 50s, with some 60s possible closer
the Chesapeake Bay and Mid-Atlantic coast vicinity during the
evening/overnight. Poor low/mid-level lapse rate also are forecast,
largely limiting instability to less than 400 J/kg MLCAPE.
Furthermore, convection developing along the eastward-advancing cold
front will be low-topped, generally below 3 km deep. Nevertheless,
convective showers could enhance surface gusts given 40-50 kt flow
in the 850-700 mb layer. Isolated gusts 50-60 mph will be possible
with stronger convective elements.
...Gulf Coast...
Strong to isolated severe storms are likely to be ongoing Sunday
morning across AL and the western FL Panhandle near the
eastward-progressing surface cold front and within a 40-50 kt 850 mb
low-level jet lifting to the northeast. Strong gusts and perhaps a
tornado will be possible with storms through around midday/early
afternoon. Thereafter, large-scale ascent will become increasing
displaced to the northeast. Vertical shear and thermodynamic
profiles become less favorable with eastward extent across GA and
northern FL as well, limiting the eastward extent of the severe
risk.
..Leitman.. 10/18/2025
Read more
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0217 PM CDT Sat Oct 18 2025
Valid 201200Z - 211200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe storms are unlikely Monday.
...Synopsis...
An upper trough over the Mid-Atlantic will lift northeast across New
England on Monday. Further west, another upper trough over the
Rockies will develop east across the Plains to the MS Valley.
Surface high pressure will be centered over the Southeast behind a
prior cold frontal passage. Surface cyclogenesis is forecast across
the Upper Midwest/Great Lakes vicinity with the approach of the
upper trough. This will result in some increased south/southwesterly
low-level flow ahead of a surface cold front sweeping southeast
across the Plains to the Upper Midwest, but Gulf moisture return
will remain scant. This will preclude much destabilization, but
cooling aloft may be sufficient for isolated lightning flashes
across parts of the Upper Midwest/Great Lakes.
Additional thunderstorms are possible across New England as a
surface low occludes/weakens and lifts northeast into Quebec.
Low-topped convection within the warm conveyor ahead of a surface
front may produce isolated lightning flashes through the daytime.
The surface front will arc southwest offshore from the
Mid-Atlantic/Southeast coast into northern/central FL. Isolated
thunderstorms will be possible across the southern FL Peninsula amid
moist/weakly unstable boundary-layer. Weak vertical shear and drying
aloft will preclude severe potential.
..Leitman.. 10/18/2025
Read more
