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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, April 15, 2023

SPC Apr 15, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1248 AM CDT Sat Apr 15 2023 Valid 151200Z - 161200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms -- capable of producing large to very large hail and damaging wind gusts, as well as a couple of tornadoes -- are possible from Missouri and the Mid-Mississippi Valley, southward to the Lower Mississippi Valley and upper Texas Coast. ...Mid MS Valley/AR... Pronounced mid-level short-wave trough is currently located over CO/NM. This feature will eject into the central/southern Plains as a strengthening 500mb speed max translates across central OK by early evening then into AR, increasing to near 85kt by the end of the period. In response to this feature, weak surface low is forecast to track from northern OK - northern MO - into northern IL Saturday evening. While the surface reflection is not expected to be particularly intense, 60F surface dew point should advance to near I70 across MO by 18z, perhaps surging into west-central IL by early evening ahead of the surface low. Early this morning, several clusters of thunderstorms have evolved over the central Plains region into western IA. Remnants of this activity should propagate into the mid MS Valley by the start of the day1 period and continue weakening as it spreads toward IL by mid day. Of more concern will be renewed convection that will evolve along/ahead of the surface low/cold front by early afternoon across eastern KS/western MO. Forecast soundings exhibit very steep surface-9km lapse rates which will aid buoyancy within a strongly sheared environment. MLCAPE values could approach 3000 J/kg across much of this region and supercells are expected to evolve fairly early ahead of the short wave. Deep-layer flow is somewhat veered so SRH values are not expected to be that strong. However, very large hail should be noted with the strongest supercells. As the front advances east, scattered convection may grow upscale into a QLCS with embedded supercells as it advances toward the MS River. Intense 12hr mid-level height falls across the mid MS Valley during the overnight hours may encourage strong convection to surge a bit farther east across IL toward IN during the overnight hours. In addition to very large hail, damaging winds and the threat for at least a couple of tornado can be expected. ...Gulf Coast Region... Latest satellite imagery depicts a short-wave trough over northeast Mexico ejecting toward south TX, in line with latest model guidance. This feature is expected to contribute to an expanding cluster of convection that should propagate from the middle/upper TX Coast, east along/just offshore of the central Gulf Coast. Northern portions of this MCS should advance across the FL Panhandle during the mid/late afternoon. Hail/wind are the primary risks with this complex. Secondary convective development is possible later in the day along the trailing cold front as it surges into southeast TX. It's not clear how far southwest convection will develop along the boundary due to weak low-level convergence, but warm surface temperatures and steep low-level lapse rates may encourage isolated storms as far west as SAT by 16/00z. Hail will be the greatest risk with this secondary development. ..Darrow/Squitieri.. 04/15/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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