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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, July 27, 2022

SPC Jul 27, 2022 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Wed Jul 27 2022 Valid 291200Z - 301200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE OZARKS/MID-SOUTH TO PARTS OF THE MID-ATLANTIC REGION... ...SUMMARY... Isolated damaging thunderstorm gusts may occur from the Ozarks/Mid-South to parts of the Mid-Atlantic region. ...Synopsis... The predominantly influential mid/upper-level feature for day 3 will continue to be progressive troughing over eastern Canada, extending into parts of the Great Lakes and Northeastern CONUS. A broad/ complex cyclone will move from its day-2 position over ON eastward across QC, with a trailing, positively tilted trough moving from the Upper Great Lakes across the Lower Great Lakes and parts of OH/PA during this period. At 30/00Z, the trough should extend from north-central QC southwestward over parts of Lake Huron and Lower MI, to eastern/central MO. The associated surface cold front is forecast by 30/00Z to reach parts of ME, Southern New England, to near or just south of the Ohio River, becoming quasistationary over the eastern/southern Ozarks, parts of OK and the TX Panhandle. Meanwhile, mid/upper-level ridging and associated weak flow aloft will cover the Southeast, southern Plains and southern Rockies, northwestward to the Pacific Northwest. ...Ozarks region to Mid-Atlantic/Northeast... Scattered to widely scattered thunderstorms are expected to develop near the front, as well as along any outflow/differential-heating boundaries left to its south by convection from day 2 into early this period. Damaging to isolated severe gusts will be the main concern. With the mid/upper trough moving away from most of the region, weak height rises are forecast aloft, albeit under flow that still should be gently cyclonic in curvature through the 500-250-mb layer. A swath of rich low-level moisture -- with PW around 2 inches or greater, as well as surface dew points commonly in the upper 60s to mid 70s F -- will combine with near-frontal lift, diurnal heating and accompanying CINH erosion, to promote multicellular clusters with sporadic damaging, wet downbursts. A series of small vorticity maxima -- some convectively induced/enhanced from day 2 -- may be moving roughly eastward along this corridor and over the surface baroclinic zone between the south-central Plains and Tidewater, aiding convective potential in mesoscale nodes. However, location specifics are too uncertain and low in predictability three days out to pinpoint denser concentrations within this lengthy corridor. Stronger flow aloft will remain over NY and New England, which still will be ahead of the positively tilted mid/upper trough and near the frontal zone, but likely with weaker moisture/instability than the previous day. While some strong convection may develop over this region, severe potential is too uncertain at this time to extend the unconditional 5%/MRGL probabilities farther north. ...Central High Plains... North of the front, the persistent easterly low-level flow component will advect moisture westward across the south-central Plains and into this region, supporting mainly afternoon/evening thunderstorm potential. Though low/middle-level flow will be weak, a well-mixed subcloud layer and the southwestern fringe of stronger upper/ anvil-level flow may aid in convective organization. At this time, lack of both greater flow and better-focused forcing precludes an unconditional threat area. ..Edwards.. 07/27/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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