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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.


Thursday, March 2, 2023

SPC Mar 2, 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 1200 AM CST Thu Mar 02 2023 Valid 021200Z - 031200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE ARKLATEX... ...SUMMARY... A regional severe-thunderstorm outbreak appears likely across parts of the southern Plains into the ArkLaTex and ArkLaMiss regions today into tonight. Widespread damaging winds, large hail, and tornadoes are all expected. A few long-lived, intense tornadoes are possible. ...Synopsis... A potent mid-level shortwave trough will traverse the southern Plains today and approach the lower MS Valley tonight while a surface low rapidly intensifies over the Arklatex. Multiple rounds of severe thunderstorms are expected through the period, with an initial round of storms moving across the Arklatex during the late afternoon and a second round moving across the Arklatex into the Lower MS Valley during the night. Ahead of the surface low, an intensifying low-level jet beneath unseasonably strong mid-level flow will promote very strong deep-layer ascent/shear atop rich low-level moisture, encouraging significant severe weather in association with both rounds of storms. A regional severe thunderstorm outbreak is expected, including the potential for damaging tornadoes. ...Central Texas into the Mid-South - Daytime... Showers and thunderstorms should be ongoing at the start of the period across eastern TX into southern AR, toward northern AL along a diffuse effective warm front, delineating the northward extent of the warm sector. As the mid-level trough traverses the southern Rockies, rapid surface cyclogenesis should ensue across TX, supporting the vigorous northward advection of rich low-level moisture into eastern OK/AR. 7-8 C/km mid-level lapse rates will overspread upper 60s F surface dewpoints, contributing to 1500-2000 J/kg MLCAPE across the warm sector. During the day, a 30+ kt low-level jet will be situated across the southern Plains, overspread by 50+ kt southwesterly mid-level flow, resulting in widespread 50-75 kt effective bulk shear across the warm sector. Appreciable low-level shear will also be present, with hodographs gradually elongating/curving throughout the day. With the mid-level trough/300 mb jet streak still lagging to the west, some questions remain in terms of how widespread diurnal warm-sector coverage will be. Nonetheless, the eastward advance of a merging dryline/pacific front will encourage at least isolated supercell storms during the afternoon into early evening, with supercells initiating across central TX into southeast OK, progressing eastward into the Arklatex. Severe gusts, large hail (including 2+ inch stones) and tornadoes are all possible. Any supercell that can become sustained within the warm sector may produce strong tornadoes. ...Arklatex into the Mid-South - Nightime... By evening, the mid-level trough will become negatively tilted and will accelerate toward the Lower MS Valley, with the surface low also expected to undergo rapid intensification. Impressive vertical wind profiles will develop as a result of the deep-layer mass response to the approaching trough, with a regional but volatile severe weather setup taking place. As the Pacific front rapidly advances eastward into a buoyant airmass (500-1500 J/kg MLCAPE, driven primarily by upper 60s F surface dewpoints), several strong to severe storms should initiate along the front. An intense QLCS may develop, comprised of a mix of embedded supercells and potentially long-lived meso-gamma scale vortices. A 50-60 kt low-level jet overspread by 100+ kts of 500 mb flow will support very large/curved hodographs amid residual surface-based instability. In addition to widespread severe gusts, several QLCS/possible embedded supercell tornadoes appear likely with this main round of storms. Given the high magnitudes of shear, at least a few sustained, strong tornadoes are likely and an intense (EF3+) tornado or two cannot be ruled out. One caveat which precludes the issuance of higher tornado-driven probabilities this outlook is the advection of warm 700 mb temperatures into the low-level jet axis during the evening, which may temper low-level updraft stretching and in turn, dampen tornado potential with a subset of storms that do occur. The QLCS may undergo gradual weakening after crossing the MS river around 09Z. Nonetheless, impressive low-level shear profiles and at least some surface-based buoyancy (albeit scant) should precede the line, with at least some risk of damaging gusts/line-embedded tornadoes continuing toward the end of the period. ..Squitieri/Darrow.. 03/02/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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