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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 1, 2024

SPC May 1, 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
0747 AM CDT Wed May 01 2024

Valid 011300Z - 021200Z


The greatest threat today for large to very large hail, severe
thunderstorm gusts and a few tornadoes will be in western Oklahoma,
the eastern Texas Panhandle and northwest/west-central Texas.

An elongated, mid/upper-level cyclone -- currently astride the
Canadian border of MT/ID -- is expected to consolidate somewhat and
move eastward slowly through the period. By 12Z, the main
circulation center should be along the MT/SK line or slightly
further north into southern SK. A series of mostly low-amplitude
shortwaves will traverse the associated, amplifying, cyclonic flow
field across the Intermountain West and Rockies. While these
perturbations should remain apart from the severe-outlook areas
today, the broader/associated regime of height falls and southwest
flow aloft will spread out over much of the central/southern Plains
through the period. A weak, but potentially important, southern-
stream trough was apparent in moisture-channel imagery from the
southern part of the AZ/NM line south-southeastward across western
Chihuahua. By 00Z, this feature is expected to reach the Big
Bend/Serranias del Burro region of southwest TX and northern
Coahuila, respectively.

The 11Z surface analysis showed a frontal-wave low near GUY, with
cold front across the northwestern/west-central TX Panhandle to
northeastern NM. A warm to stationary front was drawn from the low
across extreme southern KS to southern MO, and should shift
northward as a warm front over central/northern KS today as the low
moves northeastward and weakens, while a new low forms over
southeastern CO. An outflow boundary was drawn from western AR
across north-central TX to northwest TX and the eastern Panhandle,
with some active reinforcement underway by convection over central/
southern OK that is elevated, per 12Z OUN sounding. A dryline
initially over the Llano Estacado near the TX/NM line should shift
eastward today to the eastern Panhandle and South Plains regions,
while remaining over the Permian Basin.

...Central/southern Plains...
Isolated, marginally severe hail is possible from elevated
convection this morning over portions of OK. Later, a potentially
complex, messy and episodic convective threat is evident over the
southern Plains, from midafternoon through overnight. The 30% area
has been modified southward somewhat but remains over what appears
to be the most favorable environment for concentrated wind/hail
threats. Swaths of strong to severe gusts are possible across a
broader area of TX/OK into late tonight, and the 15% area has been
expanded mainly on the southeast side.

Scattered thunderstorms are expected to form near the dryline this
afternoon from southwestern/central KS to southwest TX, and move
generally eastward, with a blend of supercell and multicell modes
during the first few hours. This is when large to very large hail
will be most probable. Damaging-wind potential should start on a
localized basis with those more-discrete early storms, then increase
from late afternoon into evening as activity congeals into a few
clusters or complexes between the Edwards Plateau and western OK. A
few tornadoes also may occur, especially with any sustained/discrete
supercells and storms near the dryline/warm-front intersection.
Additional development is possible late this afternoon into tonight
ahead of the dryline -- across parts of south TX and the Serranias
del Burro region ahead of the southern-stream perturbation aloft.
This also may grow upscale into strong-severe clusters, forward
propagating eastward over south-central/southeast TX, with damaging
gusts being the main concern.

A substantial factor (and lingering uncertainty) in bounding
substantial severe potential on the north end will be the position
and character of the outflow boundary/boundaries from yesterday
night's MCS activity in southern and northern OK. Each complex
yielded substantial theta-e deficits in their resulting cold pools,
with related drying still manifest as upper 50s to low 60s F surface
dewpoints from the DFW Metroplex across much of OK. Return flow of
much richer moisture is expected around the western rim of that
modified air mass, which itself should advect northward through
parts of OK today. Strong heating, steep low/middle-level lapse
rates and favorable moisture should yield MLCAPE in the 2500-3500
J/kg range near the moist axis, amidst 25-40-kt effective-shear
magnitudes and somewhat-favorable hodographs for supercells.
However, the most-favorable sector over the western OK/eastern
Panhandle region -- and especially into KS south of the warm front
-- may be narrow, limiting eastward extent of organized severe
threats after initial dryline activity. Farther south, more
clustering and forward propagation are expected with greater
eastward reach, with the moist sector having not been modified as
much, or at all, by the prior MCS outflow.

..Edwards/Leitman.. 05/01/2024

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)