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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.


Thursday, June 29, 2023

SPC Jun 29, 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 1255 AM CDT Thu Jun 29 2023 Valid 291200Z - 301200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF SOUTHERN IOWA AND FAR NORTHEASTERN MISSOURI ACROSS ILLINOIS...TO SOUTHWESTERN PORTIONS OF INDIANA AND PARTS OF NORTHERN KENTUCKY... ...SUMMARY... Severe storms producing damaging winds and large hail are possible across the region from southern Iowa southeastward to Kentucky. A couple tornadoes may also occur. Large to locally very large hail and damaging wind gusts are also expected from southeastern Wyoming/northeastern Colorado eastward into the central Plains, with a tornado or two possible. ...Synopsis... A belt of enhanced mid-level flow is forecast to persist from the central High Plains to the Midwest/Ohio Valley, with the mid-level height gradient between the southern U.S. ridge and central Canada trough. This enhanced flow will support a roughly coincident zone of severe-weather risk through the period. At the surface, a baroclinic zone extending from the Upper Mississippi Valley vicinity to the central Plains, and then into the central High Plains region, will make little progress through the period. Elsewhere, high pressure will largely prevail. ...Southern Iowa across the Illinois/Indiana/Kentucky vicinity... Thunderstorms will likely be ongoing at the start of the period, roughly in the eastern Nebraska/southwestern Iowa vicinity. Other storms will likely be evolving across parts of the Illinois/southwestern Indiana vicinity early in the period as well. At this time, it appears that the Missouri Valley-area storms will further organize and move eastward through the morning and into the afternoon, posing risk for strong/damaging winds. This risk will be aided by likely-to-be fast-moving storms, given increasingly strong deep-layer westerlies progged to be spreading across this area. Meanwhile, as this convection moves eastward, a more complex evolution of storms is expected across the Midwest/lower Ohio Valley area. Various CAM runs show differing convective evolutions, but overall, likelihood for multiple rounds of southeastward-moving storm clusters exists, as the aforementioned strong deep-layer flow field spreads eastward/southeastward with time. The result will be the potential for fairly widespread severe-caliber wind gusts, along with large hail and potential for a couple of tornadoes, with these severe events accumulating from multiple rounds of strong/severe storms continuing throughout much if not all of the period. ...Central High Plains/central Plains... Northeast of a surface baroclinic zone backed into the central High Plains region, the upslope flow regime across southeastern Wyoming and into eastern Colorado will continue today. Once again, diurnal heating of a moist boundary layer to the cool side of the front will yield moderate destabilization, with around 2000 J/kg mixed-layer CAPE expected by mid afternoon. This will support development of isolated storms, similar to the previous couple of days, and initially near the Laramie Range. As storms increase gradually in coverage with time, deep-layer shear (augmented by 40-plus kt west-southwesterlies at mid levels) will result in an expanding risk for very large hail and locally damaging wind gusts, along with potential for a tornado or two. With time organized/supercell storms may congeal/grow upscale into the evening, and move eastward across the Nebraska/northern Kansas vicinity. As such, risk for damaging winds, and some hail, may continue/spread eastward through much of the overnight period. ..Goss.. 06/29/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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)