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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.

Monday, March 21, 2022

SPC Mar 21, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Mon Mar 21 2022 Valid 212000Z - 221200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF CENTRAL/EAST TEXAS... ...SUMMARY... Several tornadoes, including the potential for a few strong tornadoes, along with very large hail and damaging winds are expected this afternoon through tonight, especially across parts of central/east Texas into western Louisiana. ...20Z Update... Severe probabilities have been trimmed on the western edge of the risk area, based on the eastward progression of the Pacific cold front/effective dryline. Otherwise, no major changes have been made to the outlook. Thunderstorm coverage and intensity is expected to increase through the remainder of the afternoon into the early evening, from northwest into central TX, with all severe hazards possible. A couple of longer-track supercells may initiate across parts of central TX late this afternoon and move northeastward, posing a threat of tornadoes and very large hail, with a couple of strong tornadoes possible. Storm modes are expected to become more linear late tonight, but a threat of damaging winds and a few tornadoes will likely persist into the Ark-La-Tex and southeast TX into Tuesday morning. See the previous outlook discussion, MCD 291, and MCD 292 for more information. ..Dean.. 03/21/2022 .PREV DISCUSSION... /ISSUED 1147 AM CDT Mon Mar 21 2022/ ...Northwest to south-central/east TX into southern OK... Have introduced a Moderate Risk (Category 4 of 5) for portions of central/east-central Texas centered on late this afternoon and evening, including parts of the Interstates 35/45 corridors. Expectations are for an initially semi-discrete supercellular mode with very large hail and some tornado potential, transitioning by evening to potential for large hail/damaging winds and tornadoes as storms spread east-northeastward with a more complex convective mode gradually evolving. At midday, a closed upper trough continues to pivot eastward, centered over southern New Mexico and nearby far northern Mexico, with the exit region of a strong mid/upper-level jet (90+ kt at 500 mb) beginning to overspread central/east Texas. Cloud cover remains rather persistent at midday within the warm sector, but this sheltering/inhibited mixing is a contributing factor to the quick north/northwestward advection of a moist air mass (70F surface dewpoints) that is already becoming increasing well-established across south-central/southeast Texas. As robust mid-level DCVA occurs with a shortwave impulse ejecting out of the basal portion of an amplified trough, surface-based thunderstorm development is initially anticipated early to mid-afternoon near the triple-point cyclone and arcing south along the dryline during the late afternoon across portions of central to south-central Texas. Cooling 500-mb temperatures and steep mid-level lapse rates should foster potential for a few semi-discrete supercells along this upper portion of the Red River Valley. Severe hail and brief tornadoes will probably be the main hazards as convection likely spreads into a less favorable environment with northern extent in Oklahoma. Convection farther southeast and south from north-central to south-central TX will have a progressively larger warm/moist sector ahead of the dryline. With MLCAPE likely to reach 1500-2000 J/kg in conjunction with an approaching 80-kt 500-mb speed max, several supercells should develop with a primary initial threat of very large hail. The bulk of guidance suggests the low-level jet will shift east-northeast during the evening which suggests that low-level hodograph curvature and attendant SRH, while adequate for tornadoes, may not be particularly large for the supercells initiating along the dryline. Nevertheless, potential remains apparently for a couple long-tracked supercells emanating from near the I-35 corridor in central/south-central Texas east-northeastward into parts of east Texas. ...Ark-La-Tex to southeast Texas... With time this evening, one or more linear clusters with embedded supercells and bowing structures should evolve from a combination of initial dryline storms and regenerative convection within the warm conveyor. A rather messy mode of severe hazards is expected to accompany this evolution with an elongated slow-moving QLCS anticipated overnight, as the primary shortwave impulse shifts towards the Lower Missouri Valley and a secondary lobe hangs back near the Texas/Mexico border. Amid an expansive swath of 50-60 kt low-level flow and rich western Gulf boundary-layer moisture, all severe hazards will remain possible through the overnight, although probably on a more isolated basis in terms of coverage. Read more CHECK UPDATE ZOOM GRAPHIC