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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.


Sunday, April 17, 2022

SPC Apr 17, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Sun Apr 17 2022 Valid 172000Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER NORTHERN LOUISIANA AND SOUTHWEST MISSISSIPPI... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF CENTRAL AND SOUTHERN TEXAS... ...SUMMARY... Large to very large hail, damaging wind gusts, and a few tornadoes, are possible over parts of the lower Mississippi Valley/central Gulf Coast region today into this evening. Severe/damaging hail will be the main threat with thunderstorms over parts of south Texas. ...20z update... Strong/locally severe storms continue over northwest LA/southern AR in an area just north of a stationary front which extends from a weak surface low over east TX across northern LA/central MS and southern AL at 20z. Please refer to MCD 514 for the latest short-term details in this area. Otherwise, the general thunderstorm line was adjusted slightly based on latest observations and frontal movement. A small cluster of severe storms continues across central TX along the westward extension of the surface front. The downstream environment should continue support supercell storm structures capable of very large hail and possibly severe gusts given MLCAPE of around 2000 J/kg and 45-50 kts of deep-layer shear. Storms should move southeast towards the San Antonio area through early evening. Over the northeast FL peninsula, the Marginal Risk area was nudged south based on ongoing strong/severe storms along a sea-breeze boundary. Storms have a history of strong wind gusts and severe hail, and some localized severe risk will continue for a few more hours. Please see MCD 513 for the latest short-term thinking in this area. ..Bunting.. 04/17/2022 .PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Apr 17 2022/ ...Synopsis... A low-amplitude trough is noted in mid-morning water vapor imagery translating eastward across the Plains. An embedded vorticity maxima/shortwave is noted within this trough moving across KS with a broad swath of subsidence overspreading the southern High Plains. Ascent associated with this feature is already overspreading the southern Plains/lower MS valley this morning with scattered showers and isolated thunderstorms noted across southeast OK in the vicinity of a diffuse surface low and ahead of a modest cold front. This activity is expected to increase in coverage and intensity through the afternoon as it propagates along a surface warm front draped to the east/southeast into the lower MS river valley. The surface cold front will continue to push into southern/southeast TX and will be the impetus for isolated thunderstorms this afternoon. ...Lower MS river valley... A moist air mass is already in place across LA/southern MS this morning with dewpoints in the low 70s. Morning soundings show this moisture extends up to around 1 km with 7 C/km mid-level lapse rates. With temperatures already warming into the upper 70s amid broken low-level cumulus, any lingering inhibition will likely erode by early afternoon with widespread 2000-2500 J/kg MLCAPE values. 12 UTC soundings also show elongated hodographs with effective bulk shear values already near 40 knots. Increasing upper-level winds attendant to the shortwave will boost deep-layer shear further across the lower MS valley by mid afternoon. The kinematic profiles will support supercells, but storm motions along the warm frontal zone will likely favor a mix of quasi-discrete supercells to one or more clusters that may amalgamate into a more organized linear mode. Regardless, the favorable thermodynamic and kinematic environment will be supportive of damaging winds and large to very large hail - particularly across north-central LA into southwest MS where the potential for more discrete modes on the edge of the best instability is greatest. A tornado threat will exist along the warm frontal zone where low-level veering wind profiles will support ESRH values near 100-150 m2/s2. ...South-central Texas... Isolated thunderstorms are expected to develop along the surface cold front as it moves into south-central and southeast TX this afternoon. Mixed layer inhibition noted in 12 UTC RAOBs will likely linger through mid/late afternoon with gradual erosion due to morning stratus across the region. Glancing ascent from the passing wave to the north combined with lift along the front should be sufficient for a handful of elevated, isolated cells late this morning with higher probability for surface based convection this afternoon. Forecast soundings show straight, elongated hodographs favorable for supercell splits, and moderate instability combined with strong effective bulk shear will support the potential for large to very large hail as well as damaging winds. While confidence in this potential remains highest across the I-35 corridor in south-central TX, the environment is supportive of severe convection from the Rio Grande through east TX. ...Northern MS through central GA... The severe hail/wind potential this morning will likely persist into the late evening and overnight hours across northern MS into central GA as the upper-level wave shifts into the southeastern CONUS. While lapse rates across this region are somewhat marginal in morning soundings, cooling aloft and strengthening upper-level winds associated with the approaching wave will support increasing instability and deep-layer shear through the day. Lift ahead of the wave and within a modest warm advection regime will support scattered thunderstorms this evening into the overnight hours. Sufficient boundary-layer moisture will be in place to support adequate MUCAPE within a sheared environment for a severe hail/wind risk. Read more CHECK UPDATE ZOOM GRAPHIC
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