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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Wednesday, May 15, 2024

SPC May 15, 2024 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Wed May 15 2024

Valid 151200Z - 161200Z



Several severe thunderstorms should move across the southern Plains
this afternoon and evening, accompanied by severe gusts (some
possibly exceeding 75 mph), large hail, and perhaps a couple of
tornadoes. Scattered severe thunderstorms are also possible this
morning into the afternoon over parts of the northern and central
Florida Peninsula, as well as the Carolinas.

A mid-level trough will progress across the Southeast as a second
mid-level trough impinges on the southern Plains today. Along the
East Coast, a weak surface low will impinge on the Atlantic
Coastline as a surface baroclinic boundary drapes across the central
FL Peninsula. Moisture advection ahead of the surface low over the
Carolinas, and south of the baroclinic boundary over the central FL
Peninsula, will encourage strong to potentially severe thunderstorm
development given the presence of adequate vertical wind shear.
Meanwhile, strong moisture advection ahead of a rapidly developing
surface cyclone over the southern High Plains will promote the
development of several severe thunderstorms by afternoon peak
heating over the southern Plains.

...Central FL Peninsula...
Thunderstorms should be initiating and strengthening along a
baroclinic boundary across northern into central portions of the FL
Peninsula by the start of the period (12Z) today. During the
morning, a 50+ kt westerly 500 mb jet streak will overspread the
baroclinic boundary, where 30+ kts of southwesterly 850 mb flow will
also be in place, contributing to curved, elongated hodographs.
30-40 kts of effective bulk shear, combined with 2000-3500 J/kg
SBCAPE (driven by 7+ C/km mid-level lapse rates overspreading mid
70s F dewpoints) could result in semi-discrete supercell structures.
However, a predominantly linear convective mode could be favored, as
the mean wind field will largely parallel the surface baroclinic
boundary. Severe wind and hail should be the main threats, though a
couple of tornadoes could also occur, especially if any supercell
structures can maintain themselves ahead of the convective line.

Ahead of the weak surface low, adequate boundary layer heating and
moistening should occur beneath 6.5-7 C/km low and mid-level lapse
rates, supporting a marginally unstable but uncapped airmass by
afternoon. The combination of surface heating and some dynamic
lifting induced by the approaching mid-level trough, will support
late morning/early afternoon thunderstorm initiation. Stronger
westerly flow aloft from the mid-level trough will overspread the
warm sector, contributing to 30-40 kts of effective bulk shear.
Also, with the onset of diurnal heating, surface temperatures
warming into the low 80s F amid mid 60s F dewpoints will boost
SBCAPE to at least 1500 J/kg. Given relatively elongated, straight
hodographs, splitting supercells and merging multicells should occur
through the afternoon, accompanied by a severe wind and hail risk.

...Southern Plains...
Surface lee troughing along the southern High Plains should become
generally more pronounced with increasing deep-layer ascent, driven
by an approaching mid-level trough. Through the afternoon, strong
diurnal heating will contribute to the development of a deep,
well-mixed, uncapped boundary layer. 8-9 C/km lapse rates will
reside in the boundary layer and into the mid-levels, resulting in
inverted-V profiles across the TX panhandle with 1500-3000 J/kg of
tall, thin CAPE. Initial storms should be high-based, with
supercells and multicells possible given modestly curved, elongated
hodographs. Large hail and severe gusts will be the initial
concerns. However, ample evaporative cooling within the deep,
well-mixed boundary layer will encourage the development of deep,
strong cold pools with a tendency to merge. Severe-wind-producing
clusters are expected to rapidly propagate from the TX/OK Panhandles
into northwestern OK and eventually southern KS by late
afternoon/early evening, preceded by richer low-level moisture and a
strengthening low-level jet. These conditions may augment severe
wind production (including the potential for 65+ kt gusts) with the
stronger storm clusters. Supercell structures may also initiate in
the warm-air advection regime along the KS/OK border during the
evening, with all severe hazards possible, before storms are
overtaken by merging cold pools from the west. Storms should
gradually weaken overnight as they either become undercut by overly
aggressive cold pools, or they outpace the buoyancy axis by the time
they reach far eastern KS/northeastern OK.

More isolated thunderstorms may initiate along a diffuse dryline
across western TX toward the Rio Grande. Given overall weak forcing,
confidence in thunderstorm development and sustenance is not overly
high. Nonetheless, over 1500 J/kg SBCAPE amid elongated hodographs
suggests that any storm that can form and mature may become
supercellular, accompanied by severe wind and hail.

..Squitieri.. 05/15/2024

SUNRISE AND SUNSET TIMES IN UTC (if you're not logged in to Google)
CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)