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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.


Saturday, May 18, 2024

SPC May 18, 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
1245 AM CDT Sat May 18 2024

Valid 181200Z - 191200Z


The most probable corridor for damaging winds is across the Florida
Panhandle to the South Atlantic Coast, this morning into the
afternoon. Isolated damaging winds and sporadic severe hail will be
possible during the afternoon into the evening across much of the
Southeast, and over parts of the Upper Midwest to eastern Kansas.

Increasing convective development is expected this morning across
the northern Gulf Coast region from LA to the FL Panhandle. This
should occur in response to isentropic ascent within the 700-mb
baroclinic zone, amid a difluent upper flow regime in the right-rear
quadrant of an intense upper jet advancing northeast over the Deep
South to southern Appalachians. Outflow from a Friday evening MCS
that decayed over south GA and north FL should serve as the primary
downstream baroclinic zone later this morning as convection
consolidates and spreads east-northeast.

Amid a relatively nebulous surface pattern due to the lack of
cyclogenesis, low-level flow outside of convective influences should
remain weak. Southwesterly deep-layer speed shear will be favorable
for occasional linear clustering through the morning into the
afternoon before convection moves off the southern Atlantic Coast.
Scattered damaging winds from strong to isolated severe wind gusts
remain possible.

Additional storms should form along the Florida Atlantic Coast sea
breeze during the afternoon with an isolated severe threat possible.
At least scattered afternoon thunderstorms are expected over the TN
Valley to southern Appalachians ahead of the primary shortwave
impulse embedded within the positive-tilt, southern-stream trough.
Uncertainty exists over the degree of destabilization in the wake of
the extensive morning convection farther south-southeast. With only
moderate deep-layer shear expected between the trough and the
mid-level jet near the Gulf Coast, have held severe wind/hail
probabilities at level 1-MRGL.

...Upper Midwest to KS...
A shortwave trough across the Prairie Provinces into the northern
Great Plains will move east into far northwest ON by early Sunday.
Attendant surface cyclone will track more north-northeastward as it
occludes, with the trailing cold front shifting east of the Upper MS
Valley and south in KS during the afternoon. Low-level convergence
along the front should be sufficient for isolated to scattered
thunderstorms, as a moderately unstable airmass with MLCAPE of
1000-2000 J/kg becomes established at peak heating.

The bulk of strong mid-level west-southwesterlies will remain
confined behind the front. Moderate deep-layer shear should
overspread the Lake Superior region, as flow substantially weakens
with southern extent. Isolated severe hail and damaging winds will
be most likely across the Upper Midwest portion of the area. Locally
strong to severe wind gusts and small hail may also occur within the
weakly sheared environment along the front into KS. The severe
threat will wane after dusk.

..Grams/Bentley.. 05/18/2024

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)