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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.


Friday, March 22, 2024

SPC Mar 22, 2024 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 AM CDT Fri Mar 22 2024

Valid 221300Z - 231200Z


Severe thunderstorm gusts, isolated large hail and a tornado or two
are possible today and tonight over parts of the Florida Keys into a
small part of southern mainland Florida.

In mid/upper levels, a slow-moving/cutoff low west of coastal
northern CA and OR will approach the coast slowly through the
period, but remain offshore until day 2. Downstream, a progressive,
split-flow pattern is evident over the central/eastern CONUS, with a
broad yet distinct northern-stream jet across parts of the Upper
Midwest, Great Lakes, and Northeast. To the south, a prominent,
southern-stream shortwave trough was apparent in moisture-channel
imagery over eastern OK and east TX, with intermittently closed
500-mb low between MLC-PRX. This perturbation should become a
purely open-wave trough today and broaden somewhat, with the trough
near a MEM-LFT axis and offshore from southwestern LA by 00Z. The
12Z/tomorrow trough position should reach to near an axis from
CHA-MGM-PNS to the central Gulf.

At the surface, 11Z analysis showed a broad area of low pressure
from north-central/northeast TX to south-central LA, including a
frontal-wave low near ARA. A cold front extended from that low
southwestward across the TX shelf waters to south of BRO, and should
sweep eastward-southeastward to the central/southwestern Gulf by
00Z, when the low reaches southern AL. A warm front -- initially
extending from the low eastward over coastal LA then southeastward
over the eastern Gulf, should move northeastward toward the north-
central/northeastern Gulf Coast and south FL/Keys today, but with
some diffusion/realignments of its baroclinicity by convective
processes. By the end of the period, the low should reach the
Piedmont of the Carolinas, with cold front over GA and the eastern

Multiple rounds of convection will cross the east-central/
northeastern Gulf through the period on either side of the warm
front. Convection should be most consistently intense over the
Gulf, but potentially brushing coastal/near-coastal parts of the
areas discussed below.

...South FL/Keys...
At least isolated severe gusts and/or hail are possible across
portions of south FL and the Keys, with the available instability
and severe threat increasing southward.

Multiple rounds of convection over the eastern Gulf should lay down
boundaries acting as both foci and poleward delimiters for organized
severe potential of upshear convection. Based on lightning,
satellite and radar imagery, the first of these complexes extends
from just offshore from APF west-southwestward to near 24N88W, with
a patchy precip shield extending eastward and northeastward over
much of the peninsula. That precip/cloud cover should blunt most of
the diabatic heating-related overland destabilization today, though
theta-e advection (especially over the Keys and vicinity) should
yield surface-based buoyancy gradually over the next several hours.

Most convection-allowing guidance has shrunk/weakened the leading
complex considerably while approaching south FL and the Keys this
morning, but also, has failed to grasp its southwestward extent so
far. As such, mesoscale uncertainty persists as to the ultimate
location and layout of the associated outflow boundary. Still, the
general idea of greater unconditional severe potential with
southward extent remains valid -- be it from the remains of the
ongoing activity or, more likely, a later MCS now over the central/
north-central Gulf and expected to turn southeastward along the
boundary and toward the outlook area, arriving tonight. Along and
south of the boundary, where the near-surface layer is least
modified by prior activity, upper 60s to low 70s F surface dewpoints
should offset modest midlevel lapse rates aloft enough to yield
1000-1500 J/kg MLCAPE by this evening. Forecast soundings suggest
favorable veering of winds with height into strong mid/upper-level
flow, with 50-60-kt effective-shear magnitudes. Damaging winds and
a tornado or two will be the main concerns.

...Southeastern LA to FL coastal bend...
An ongoing, predominantly elevated area of thunderstorms -- from
portions of southeastern LA southwestward across the LA shelf waters
-- should proceed eastward near the north-central/northeastern Gulf
Coast today. Additional development is possible to its east, also
over shelf waters and/or the Gulf Coast. Isolated, marginally
severe gusts or hail may occur.

Activity should continue to move eastward in step with partial
destabilization/recovery in the form of low-level warm advection and
moisture transport, around and atop outflow from a complex of
thunderstorms now over the east-central open Gulf. Enough theta-e
recovery in low levels has occurred to support continued
organization of the main MCS near the LA coastline, but at strong/
subsevere levels. This general trend should continue as activity
shifts eastward across coastal MS/AL/FL Panhandle and offshore,
amidst 60-70-kt effective-shear magnitudes and strong midlevel winds
supporting fast convective translation. As such, momentum transfer
from midlevels (via rear-inflow-jet processes or directly in
individual/embedded downdrafts) may produce gusts capable of
penetrating to the surface near severe levels. Favorable deep shear
and lapse rates aloft also will persist eastward for hail production
aloft, some of which may reach the surface near severe limits as

..Edwards/Grams.. 03/22/2024

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)