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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.


Monday, April 8, 2024

SPC Apr 8, 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
0743 AM CDT Mon Apr 08 2024

Valid 081300Z - 091200Z


Multiple rounds of severe thunderstorms should develop from mid
afternoon through tonight across a large portion of the southern
Plains into the Mississippi Delta region. Large to giant hail is
the main threat, especially over northwest Texas, though a few
tornadoes and severe gusts are also possible in an area extending
east into northern Louisiana.

Morning water-vapor imagery shows a positively-tilted mid-level
trough over the Desert Southwest/northwest Mexico. This mid-level
trough will amplify as it moves across the Southwest and northern
Mexico. An associated belt of strong southwesterly flow will extend
from the base of the trough across the southern Great Plains and
into the lower MS Valley. A cyclone will develop in West Texas and
deepen through the period as southerly low-level flow advects rich
moisture into TX/LA [near the record high lowest 100-mb mean mixing
ratio observed this early in the year at the Brownsville raob site
(17.2 g/kg)]. A warm front will advance northward to the Red River
by early evening. A cold front analyzed this morning moving south
through the TX Panhandle/western OK will become stationary later

...Northwest Texas into north-central Texas...
Strong heating on the northwest periphery of rich low-level moisture
will weaken the cap across northwest TX by mid afternoon. Forecast
soundings indicate a moderately unstable airmass (1000-2500 J/kg
MLCAPE) will continue to destabilize into the evening as
south-southeasterly flow strengthens and advects 50s (west) to mid
60s (near I-35) surface dewpoints into the region by early evening.
Veering and strengthening flow with height (100+ kt at 250 mb) will
favor supercells as the initial convective mode. Large to giant
hail (3-4 inches in diameter) is possible in addition to some
tornado risk towards evening. Some consolidation into a cluster/MCS
may occur during the evening across north-central TX with some risk
for all 3 hazards.

...East Texas into the ArkLaTex...
Moderate to strong instability is expected to develop across east
Texas and into western Louisiana this afternoon as upper 60s to near
70s dewpoints advect northward. Despite a solar eclipse across this
region, its impact on the overall severe weather threat will likely
remain minimal. Only moderate warming will be sufficient to erode
inhibition across the region with a gradual strengthening of
southerly 850-mb flow and isentropic ascent as the primary focus for
storm development by mid to late afternoon.

Strong instability and shear is expected and will support
supercells capable of large to very large hail. However, there are
some concerns about storm interference and updraft longevity.
Initially, a warm nose around 700mb is evident on NAM/RAP forecast
soundings which may limit more robust updraft development. This warm
nose is forecast to erode by 23/00Z. However, by that time,
widespread shower/thunderstorm development may be underway which
could be a limiting factor to updraft longevity and a greater
tornado/large hail threat.

Some guidance suggests a MCS may develop out of the
northwest/north-central Texas convection and move through northeast
Texas during the overnight hours. This solution will greatly depend
on the evolution of earlier convection and position of the
convectively enhanced warm front by late evening.

...Texas Hill Country overnight...
Increasing forcing for ascent via stronger mid-level height falls
will overspread much of western/central Texas tonight. Continued
moistening with mid-upper 60s deg F dewpoints beneath steep 700-500
lapse rates (8 deg C/km) will result in 2500 to 3000 J/kg MUCAPE.
Elongated hodographs with 60-kt effective shear will promote
supercells and mainly a risk for large to very large hail.
Southerly 850-mb flow will increase overnight via a LLJ and act to
augment initially limited hodographs. If a cluster organizes
overnight (06-12z), a risk for severe gusts and perhaps a tornado
could develop. Have extended Slight Risk equivalent wind/tornado
probabilities southward for this potential scenario.

...West Texas early Tuesday...
The dryline is expected to retreat into West Texas overnight with
strong instability building back to near Midland early Tuesday
morning. As strong upper forcing overspreads this region, at least
isolated to scattered storms will probably develop on the western
periphery of a strongly unstable/sheared environment. Have adjusted
the some of the severe probabilities farther west where the progged
western edge of moisture/buoyancy will be located.

..Smith/Mosier.. 04/08/2024

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)