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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, July 21, 2023

SPC Jul 21, 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 1249 AM CDT Fri Jul 21 2023 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHEAST... ...SUMMARY... Severe thunderstorms with wind damage and hail will be possible today across parts of the Southeast. Marginally severe storms will also be possible in parts of the Northeast and High Plains. ...Southeast... Mid-level flow will be west-northwesterly today across much of the central and eastern U.S. At the surface, a moist airmass will be in place across much of the Southeast with surface dewpoints in the lower to mid 70s F. Moderate instability will quickly develop this morning, with a gradient of instability extending east-southeastward across the Gulf Coast States. A shortwave trough will approach the unstable airmass this morning. Large-scale ascent associated with this feature will support a morning MCS located in the southern Plains at the start of the period. The MCS is forecast to gradually intensify during the day, moving east-southeastward along a gradient of moderate instability. RAP forecast soundings around midday along the track of the MCS from eastern Arkansas into north-central Alabama have MLCAPE increasing to around 3000 J/kg. The soundings have veered winds in the low to mid-levels, and increasing winds with height to about 40 knots at 500 mb. This wind profile will likely support the development of a linear MCS with a wind-damage threat. The potential for wind damage is expected to increase as low-level lapse rates steepen in the afternoon. The MCS is expected to remain organized as it tracks across the central Gulf Coast states this afternoon, reaching the southern Atlantic Seaboard by early evening. ...Northeast... An upper-level trough will move eastward across the lower Great Lakes and Mid-Atlantic today. At the surface, an associated cold front will advance eastward into the region. Ahead of the front, surface dewpoints in the lower to mid 70s F, will contribute to the development of a pocket of moderate instability. Storms are expected to form near and ahead of the front, moving eastward into the instability during the afternoon. Forecast soundings along the axis of instability from eastern Maryland northward into New Jersey have 0-6 km shear around 30 knots, along with 0-3 km lapse rates approaching 7.5 C/km. This should support marginally severe multicells with an isolated wind-damage threat. Although the greatest potential for isolated wind damage may be in the Mid-Atlantic, a marginal wind-damage threat could develop as far north as western New England this afternoon. ...High Plains... Northwesterly mid-level flow will be in place today across the High Plains. At the surface, flow will be upslope across the southern and central High Plains. In response, a moist airmass will be in place across eastern Colorado. As surface temperatures warm, scattered thunderstorms will develop in the higher terrain of central Colorado and move southeastward into the central High Plains. MLCAPE across the central High Plains is forecast peak in the 1000 to 1200 J/kg range this afternoon. 0-6 km shear is expected to range between 25 and 35 knots, suggesting that an isolated severe threat could develop. Hail and strong gusty winds will be possible with the stronger multicells. ..Broyles/Wendt.. 07/21/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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