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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, May 18, 2022

SPC May 18, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Wed May 18 2022 Valid 182000Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MIDWEST...CENTRAL/SOUTHERN PLAINS...AND KENTUCKY... ...SUMMARY... A couple tornadoes along with scattered damaging winds and severe hail remain possible across Kentucky and vicinity late this afternoon and early evening. Scattered severe winds, a couple of which may be significant, may occur from southeast Colorado to the Kansas/Oklahoma border area from late afternoon into tonight. Isolated to scattered large hail and damaging winds are also possible across northeast/east-central Minnesota into northwest Wisconsin during the late afternoon to early evening. ...20Z Update... Have trimmed severe probabilities behind an MCV with associated small cluster of thunderstorms ongoing along the IN/KY border area. If this activity can become surface based, then it would pose a threat for damaging winds, hail, and perhaps a tornado. The potential for additional severe thunderstorms to develop on the southwest flank of the MCV in western/central KY remains unclear. See Mesoscale Discussion 812 for more details on the near-term severe threat across this area. Elsewhere, generally minor changes have been made to the outlook to account for latest observational trends and short-term model guidance. Still, overall forecast reasoning remains unchanged. Mesoscale Discussion 813 contains more information on the short-term severe risk across MN, while Mesoscale Discussion 814 details expected convective evolution across eastern CO and vicinity this afternoon. Mesoscale Discussion 815 has additional details on the isolated wind threat across north-central NE over the next couple of hours. ..Gleason.. 05/18/2022 .PREV DISCUSSION... /ISSUED 1127 AM CDT Wed May 18 2022/ ...KY vicinity to the MO/AR border... A pronounced MCV over southern IL will track east across the OH Valley towards the central Appalachians through this evening. Primary severe potential should eventually emanate out of the south-southwest flank of the MCV where some cloud breaks should support surface-based destabilization in tandem with a plume of low to mid 60s boundary-layer dew points spreading east. A fairly tight gradient in MLCAPE is anticipated from west to east by late afternoon. A couple supercells should develop in this time frame amid enhanced low to mid-level flow attendant to the MCV. A threat for all severe hazards is possible, although the overall spatial distribution will likely remain isolated and temporally confined, in addition to delays in low-level destabilization which could limit intensity. Some west/east-oriented clustering may linger during the evening, but the severe threat should wane after the MCV outpaces the plume of diurnal destabilization. Farther west, isolated thunderstorm development will be possible this evening along the effective baroclinic zone near the MO/AR border. Forcing for ascent will be weak/shallow and confined to the front, so storm development/coverage is uncertain. However, mid-level lapse rates of 8-9 C/km, MLCAPE greater than 3000 J/kg, and mid-level flow near 40 kt will support a conditional threat for large hail and damaging winds. ...Southeast CO to northern OK... A cluster of high-based storms appears probable across southeast CO by mid to late afternoon, immediately east of the mountains in a zone of weak upslope flow and strong surface heating/deep mixing. Rather deeply mixed, inverted-V thermodynamic profiles with DCAPE greater than 1200 J/kg, will favor strong downdrafts and the potential for a storm cluster with occasional severe outflow gusts of 60-75 mph from southeast CO into the OK Panhandle this evening. Guidance is fairly consistent that the MCS will impinge on a plume of richer low-level moisture arcing westward across northern OK. This should help sustain a convectively generated MCV and maintain the surface cold pool eastward along the southern KS/northern OK border area. At least an isolated severe wind and some hail risk should linger overnight in northern OK. ...Northeast/east-central MN and northwest WI... A shortwave trough near the ND/Manitoba border will progress towards the Upper Great Lakes through tonight. Attendant surface cyclone should largely track along the MN/Ontario border with a reinforcing cold front to its south-southwest sweeping east. Despite limited low-level moisture on the larger scale, a corridor of low to mid 50s surface dew points combined with abundant boundary-layer heating beneath steep mid-level lapse rates and cooling mid-level temperatures (colder than -20 C at 500 mb) will support MLCAPE approaching 1000 J/kg with minimal convective inhibition. Effective bulk shear of 40-50 kts with mainly straight hodographs and the modest buoyancy will be sufficient for at least a few supercells capable of large hail and isolated damaging winds. This threat will diminish rapidly after dusk. ...Central NE and far south-central SD... Convergence along the trailing portion of the aforementioned reinforcing cold front may be sufficient for isolated thunderstorms during the late afternoon to early evening. While buoyancy will be weak, adequate deep-layer shear and a steep low to mid-level lapse rate environment will support potential for isolated, marginally severe hail and wind. Read more CHECK UPDATE ZOOM GRAPHIC