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Weather conditions directly above are near Lakefront. Top tabs refer to O'Hare (official).

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.

Sunday, September 11, 2022

SPC Sep 11, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Sun Sep 11 2022 Valid 112000Z - 121200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential should remain low through tonight. ...20Z Update... Thunderstorm probabilities have been removed across parts of the Mid-South and Midwest behind a cold front advancing eastward. Otherwise, no changes have been made to the ongoing forecast. While sporadic strong wind gusts may occur with any convection that develops/persists across the eastern CONUS through the early evening, overall severe potential should remain low. ..Gleason.. 09/11/2022 .PREV DISCUSSION... /ISSUED 1103 AM CDT Sun Sep 11 2022/ ...Synopsis... Mid-morning surface observations and satellite imagery clearly show the east/southeastward progression of a cold front into the MS River Valley. Modest cold advection following this front will continue to drive weak height falls aloft over the central CONUS over the next 24 hours, leading to a gradual deepening of the upper wave over the Midwest. Surface analyses also show the front surging relatively faster across the lower MS River Valley/eastern southern Plains compared to locations closer to the surface low over southern Lake Michigan. This suggests that the occlusion process has likely begun and will continue through the day. Despite this, the amplification of the upper air regime will support gradual deepening of the nearly stationary surface low over northeast IL through tonight. Thunderstorms have already begun to develop along the cold front, and will expand in coverage through the afternoon hours as the front pushes east through the OH Valley region. Across the northern Gulf coast, a decaying cut-off low will migrate east/northeast through the day. Ample moisture advection associated with this feature combined with weak/broad ascent and areas of daytime heating/surface-based destabilization will support another day of scattered thunderstorms from FL northward to the Mid-Atlantic coast. Unseasonably high moisture associated with the remnants of Tropical Storm Kay will continue to foster thunderstorm chances across a broad area of the Southwest today. Stronger wind gusts are possible with any thunderstorm moving into a well-mixed region, but weak flow aloft will limit the probability of numerous severe gusts. ...Middle OH River Valley.. Morning RAOBs ahead of the cold front across the OH River Valley show ample boundary-layer moisture, but weak low and mid-level lapse rates. Extensive cloud cover will likely hinder surface-based destabilization for much of the day. However, evidence of elevated instability with limited inhibition is noted in observed and forecast soundings, as well as latest satellite trends. The deepening of the upper low will support increasing flow and elongating hodographs above 3 km through the day, which may provide adequate effective shear for a few stronger, more organized cells or clusters. If storms can become rooted within the boundary, a few strong wind gusts may occur. This will be most likely for areas that can see surface temperatures warm through the mid/upper 70s, but confidence in a sufficiently widespread severe risk remains too limited to introduce probabilities. Read more CHECK UPDATE ZOOM GRAPHIC
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