SPC Apr 14, 2025 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0249 PM CDT Mon Apr 14 2025

Valid 142000Z - 151200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS WEST
VIRGINIA AND VIRGINIA...

...SUMMARY...
Scattered strong to severe storms ongoing this afternoon will
continue through early tonight from the Upper Ohio Valley eastward
to the Mid-Atlantic. Large hail, severe wind gusts, and a couple of
tornadoes are likely.

...20z Update OH Valley and Appalachians...
Afternoon satellite imagery shows several areas of convection
developing beneath a broad upper low over parts of the Midwest,
Great Lakes and Ohio Valley. Initial storms across IN/OH/KY will
continue to mature as the cold front moves east. Upper 50s to low
60s F dewpoints and steep mid-level lapse rates beneath the upper
low will support around 1000 J/kg of MLCAPE. 40-50 kt of effective
shear, but veered low-level flow will support a mix of supercells
and linear clusters. Hail and damaging winds appear likely, along
with a risk for a couple tornadoes. Storms will spread east into the
Mid Atlantic this evening, mainly with a risk for damaging gusts.
Minimal changes were made to the outlook area on the western edge to
capture storm development farther west along the front.

...Midwest...
Near the core of a secondary vort max over the northern Plains,
broad-scale ascent was supporting scattered low-topped convection
across parts of SD, NE, and northwestern IA. Strong mid-level flow
will continue to move south as a mid-level jet intensifies. Despite
the limited surface moisture, the relatively cold mid-level
temperatures and strong ascent will favor some threat for small hail
and damaging gusts with shallow storms. Have adjusted the Marginal
southward across central IA where weak buoyancy (MUCAPE 200-300
J/kg) may allow storms with damaging gust potential to persist
farther south this evening.

..Lyons.. 04/14/2025

.PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Apr 14 2025/

...Upper OH Valley this afternoon into VA early tonight...
Recent satellite imagery depicts a maturing mid-latitude cyclone
moving eastward across Lake Superior towards northeastern Ontario
with an upstream shortwave trough moving through the northern
Plains. Expectation is for the cyclone to continue
deepening/maturing as it moves into and through northeastern Ontario
today, while the upstream shortwave progresses quickly southeastward
through the Mid MO Valley and into the Mid MS Valley. As this
occurs, strong mid-level flow will spread eastward across the OH
Valley and over the Northeast and Mid-Atlantic States. 

At the same time, a cold front will spread eastward across the OH
Valley this afternoon and evening, and across the central
Appalachians tonight. Current surface analysis reveals upper 40s to
low 50s dewpoints ahead of the front in the Middle OH Valley, with
the upper 50s/low 60s dewpoints farther southwest over western KY.
This greater low-level moisture is expected to surge northeastward
amid the moderate southwesterly low-level flow, combining with
evapotranspiration to bring upper 50s dewpoints into upper OH Valley
ahead of the front. 

This increase in low-level moisture combined with daytime heating
should be enough to destabilize the airmass ahead of the front
across the Upper OH Valley. Forcing for ascent (from a combination
of increasing large-scale ascent and forcing along the front) will
increase across this destabilized area, supporting thunderstorm
development during the afternoon. An initially cellular mode is
anticipated, with steep mid-level lapse rates and long hodographs
potentially resulting in a few supercells. Primary severe risk with
these supercells is large hail of 1-2 inches in diameter. Some
damaging gusts and a tornado or two are possible, although the lack
of higher low-level moisture will mitigate the overall tornado
potential. Strong outflow and increasing mid-level flow suggest a
transition to a more linear mode is likely, with several bowing
segments possible. There is also some potential for the development
of a singular, more coherent convective line. In either case, a
transition from hail to damaging gusts as the primary severe risk is
anticipated as this activity spreads eastward. Clusters/line
segments will likely persist east of the Appalachians into VA
through early tonight, though the severe threat will diminish with
eastward extent and after 03z. 

...SD to IA this afternoon/evening...
Low-level moisture will be limited, but surface heating beneath
cooling midlevel temperatures will support weak surface-based
buoyancy and the potential for low-topped showers and a few
thunderstorms from SD into IA (in advance of a digging shortwave
trough now over western ND/eastern MT). Relatively cold temperature
profiles will favor some threat for small hail, while steep
low-level lapse rates and 30+ kt flow through the mixed layer favor
gusty outflow winds of 40-50 mph.

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