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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, April 5, 2023

SPC Apr 5, 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 1252 AM CDT Wed Apr 05 2023 Valid 051200Z - 061200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM LOWER MI ACROSS THE MIDDLE/LOWER OH VALLEY INTO THE MID-SOUTH... ...SUMMARY... Scattered severe storms posing a risk for tornadoes and large hail are expected in a corridor across eastern Illinois through Lower Michigan today. Additional thunderstorms accompanied by potentially damaging wind gusts, hail, and a few tornadoes are possible from Ohio Valley into the Lower Mississippi Valley. ...Synopsis... Current satellite imagery shows deep upper troughing across the western CONUS, with a strong shortwave trough moving through the northern/central Plains. This shortwave is expected to continue northeastward into western Ontario while maturing into a deep mid-latitude cyclone. A large area of enhanced southwesterly flow aloft will accompany this cyclone, stretching from the southern Plains into the Upper Great Lakes/OH Valley. Surface low associated with this cyclone is currently over central IA. Expectation is for this low to progress quickly north-northeastward into WI while occluding. An additional triple-point low is forecast to progress more northeastward, taking it across northern Lower MI and into northeastern Ontario. An associated cold front, which will likely extend from southern WI southwestward through the TX Hill Country during the early morning, will progress eastward/southeastward. As it does, it will interact with a broad warm sector that extends across much the MS and OH Valleys, supporting numerous thunderstorms throughout the day. ...IL to OH and Lower MI... Thunderstorms will likely be ongoing ahead of a composite outflow boundary at the start of the period, which is expected to extend from northern Lower MI southwestward into northern IL. An early morning hail risk is possible ahead of this boundary from eastern IL into southern Lower MI, where prefrontal storms should encounter an environment characterized by steep mid-level lapse rates and strong vertical shear. Some tornado risk would exist with these storms as well, particularly if a semi-discrete mode can be realized later into the morning when surface temperatures should be slightly warmer. Strong low- to mid-level flow will support a damaging wind gust potential with both the prefrontal storms and more linear development along the composite outflow. Some additional development is possible over this region later in the afternoon as the primary cold front pushes through. Strong wind fields will be in place, leading to some potential for damaging gusts. However, only limited air-mass recovery is expected, and mid-level temperatures will likely be relatively warm from the preceding convection. These factors are currently expected to keep storm coverage limited. ...Mid/Lower MS Valley...East/Southeast TX... Large-scale forcing for ascent will become increasingly displaced north of the region, with storm outflow becoming the primary mechanism pushing the front eastward. Buoyancy will be greater here than areas farther north, and shear will remain moderate. As a result, the potential for severe thunderstorms still exists despite the weaker large-scale forcing. Damaging gusts are the primary severe risk, although lapse rates will be steep enough to support hail, particularly if cell mergers result in brief updraft intensification. Low-level shear is strong enough to support a low-probability tornado threat as well, although the linear, outflow-dominant storm mode will mitigate the overall potential. ...Middle/Upper TX Coast into the Lower MS Valley... Thunderstorms are expected to develop during the evening and overnight as modest warm-air advection occurs along the stalled front from the middle TX Coast into the Mid-South. Steep mid-level lapse rates may still be in place, supporting enough buoyancy for isolated hail. ..Mosier/Thornton.. 04/05/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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