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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.


Wednesday, September 22, 2021

SPC Sep 22, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0238 PM CDT Wed Sep 22 2021 Valid 222000Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF EASTERN OHIO...WESTERN PENNSYLVANIA...AND NORTHERN WEST VIRGINIA... ...SUMMARY... The greatest potential for damaging to severe thunderstorm winds and a few tornadoes today will be over parts of Ohio, West Virginia and western Pennsylvania. ...20Z Update... ...Upper OH Valley... Recent surface analysis places a deepen low near the OH/WV/PA border intersection, along the leading edge of a cold front pushing eastward across the OH Valley. Overall instability remains modest ahead of the front, but still sufficient for updrafts deep enough to produce lightning. Additionally, the clearing across southwest PA has allowed temperatures to climb into the low 80s, fostering locally higher buoyancy in this region. Vertical shear remains strong and the threat for embedded bowing structures capable of damaging wind gusts and a tornado or two is expected to persist throughout the afternoon into the early evening. ...VA and Carolinas... As mentioned in recently issued MCD #1776, a couple damaging gusts may accompany the stronger storms through the remainder of the afternoon. However, any severe threat is expected to isolated and/or brief given the limited vertical shear. ..Mosier.. 09/22/2021 .PREV DISCUSSION... /ISSUED 1107 AM CDT Wed Sep 22 2021/ ...Upper OH Valley... A deep upper trough is moving slowly eastward across parts of IL/IN/KY today, with an associated surface cold front extending from central OH southward into east TN and northern GA. A pocket of partly cloudy conditions has developed ahead of the front from central WV into eastern OH and western PA. Continued afternoon heating/destabilization will yield MLCAPE values of 1000-1500 J/kg. A surface low along the front over OH will deepen today as it tracks into western PA. Backing/strengthening low-level winds ahead of the low will enhance convergence and aid in the development of thunderstorms along the cold front. Shear profiles will be rather strong, posing the risk of supercell and bowing structures capable of damaging winds and a few tornadoes. Storms should weaken by early evening as they move into more stable air over central PA. ...VA and Carolinas... The aforementioned surface cold front will move across the mountains of western VA/NC this afternoon. Warm and humid conditions ahead of the front will result in thunderstorm development. Low and deep-layer wind fields in this region are weaker than farther north, suggesting storms will be less organized. Nevertheless, isolated intense cells may develop, with locally damaging winds possible. Read more LIVE:
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