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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.


Saturday, September 2, 2023

SPC Sep 2, 2023 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Sat Sep 02 2023 Valid 021300Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected. ...Synopsis/Discussion... In mid/upper levels, the main belt of westerlies will remain largely confined to Canada and the Great Lakes/Northeast this period -- well-removed from optimal low-level moisture still relegated to portions of the Gulf Coast States and southward. South of those westerlies, a split, blocky pattern will persist, with minor adjustments from yesterday. Although a high aloft will remain over the south-central Great Plains, a small, cut-off cyclone now centered near SHV should meander west-northwestward toward the Red River region north of DFW. General thunderstorms will remain possible to its southeast, over much of the Gulf Coast region, amid difluent flow, lift near residual low-level frontal zone across the region, and rich low-level moisture. Elsewhere, a prominent, cut-off, mid/upper-level cyclone is apparent in moisture-channel imagery over much of OR, CA and NV, with a center near Cape Mendocino. For most of the period, the cyclone will meander near its present position, while weakening very gradually. Near the end of the period, as a northern-stream shortwave trough moves quickly southeastward down the BC Coast, the cyclone will begin to open up and shift slightly eastward, heralding its substantial deamplification and acceleration on day 2. ...Lower Colorado River Valley to Great Basin.... Widely scattered to scattered thunderstorms are expected through this evening over a large area of the interior West, likely peaking in coverage late this afternoon. This potential will be associated largely with a broad plume of nearly southerly deep-layer flow east of the cyclone, and associated moisture transport and warm advection. Two areas of interest exist with conditional potential for isolated severe gusts or hail, but not organized/focused enough for an outlook area this cycle: 1. Lower Colorado and Imperial Valley regions, where the greatest buoyancy will exist amid strong diabatic heating and rich low-level moisture (upper 60s to mid 70s F lower-elevation surface dewpoints). Those factors, along with a deep troposphere, will yield negligible MLCINH beneath 2000-3000 J/kg MLCAPE and strongly difluent mid/ upper-level flow southeast of the coastal cyclone. However, deep- layer flow will be weak, along with vertical shear, limiting organization. Strong pulse downdrafts may occur from the most intense multicell convection. 2. Central/northern NV, where afternoon heating, moisture and instability will be more limited than farther south, but still perhaps adequate for some surface-based convection. Some of the resulting thunderstorms may exhibit at least transient supercellular characteristics in closer proximity to the eastern part of the cyclonically enhanced flow field aloft, where 35-45 kt effective- shear magnitudes and 500-800 J/kg MLCAPE are possible. Lack of greater buoyancy for that shear suggests that any severe threat remains too isolated and conditional for an outlook area. ..Edwards/Leitman.. 09/02/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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