Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 08 2024 19:56:36 ACUS01 KWNS 081956 SWODY1 SPC AC 081954 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0154 PM CST Thu Feb 08 2024 Valid 082000Z - 091200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF FAR EASTERN IOWA...NORTHERN ILLINOIS...AND SOUTHERN WISCONSIN... ....SUMMARY... A few strong/severe thunderstorms remain possible this afternoon through early evening across parts of far eastern Iowa, northern Illinois, southern Wisconsin, and the southern Lake Michigan vicinity. ....20Z Update... Recent surface observations show upper 40s surface dewpoints present across southern/central IL and vicinity, with clearing occurring across parts of eastern IA and western/central IL beneath a mid-level dry slot. Recent visible satellite imagery also shows shallow cu development across northeastern MO and central/eastern IA as large-scale ascent attendant to an upper trough overspreads the warm/moist sector. Current expectations are for isolated, low-topped thunderstorms to develop by 22-23Z across far eastern IA and northern IL. Even though low-level moisture will likely remain shallow/limited, with surface dewpoints generally in the mid to upper 40s, rather cold mid-level temperatures and steepened lapse rates aloft should still aid in the development of around 500 J/kg of MLCAPE. Coupled with strong deep-layer shear, this weak instability should support organized convection, including the potential for a supercell or two. Isolated severe hail, strong/damaging winds, and perhaps a tornado all appear possible with this activity as it spreads quickly northeastward across northern IL and southern WI through the early evening before weakening. Given the limited thermodynamic environment and latest surface observations, have maintained the Marginal Risk with no changes. ...Gleason.. 02/08/2024 ..PREV DISCUSSION... /ISSUED 1030 AM CST Thu Feb 08 2024/ ....Synopsis... A mid-level short-wave trough now crossing the Middle Missouri Valley/central Plains will continue progressing northeastward today and tonight, while a second feature now in the vicinity of the Lower Colorado Valley shifts eastward through the period. Meanwhile, upper ridging over the East will be shunted progressively eastward by the aforementioned advance of short-wave troughs farther west. At the surface, a rather deep (990 mb) surface cyclone is currently analyzed near the ND/SD/MN border intersection, with a cold front extending southward across the Middle Missouri Valley into Kansas. This boundary, and the advance of the upper trough, may support isolated late afternoon strong/potentially severe convective development across eastern Iowa/northwestern Illinois. Elsewhere, showers and scattered thunderstorms are expected to evolve across the Four Corners states ahead of the aforementioned upper trough, and overnight thunder may evolve within an area of broad/weak QG ascent over parts of the Lower Mississippi and Tennessee Valleys. Severe weather is not expected in these areas. ....Eastern Iowa/northern Illinois/southern Wisconsin vicinity... Low-level moisture remains a primary uncertainty today, with respect to potential strong/severe storm development. Dewpoints remain in the upper 30s/low 40s across the Iowa/Illinois area, where model forecast soundings -- particularly the RAP -- have consistently indicated upper 40s to low 50s dewpoints by late afternoon. This degree of moistening still appears to be a bit aggressive, with middle to upper 40s largely anticipated. With that said, very cold air aloft/steep lapse rates will continue to overspread this region, and the deep-layer wind field is conditionally quite supportive of severe/supercell storms. At this time, we will maintain MRGL risk and all-hazard, low-probability outlook. A couple of storms may develop by late afternoon, in the eastern Iowa/northwestern Illinois vicinity, and then shift eastward/east-northeastward through early evening, before weakening. However, evolution of moisture through the day will be closely watched, as the more aggressive RAP model solution -- should it appear more likely to occur -- would require consideration for an upgrade to the outlook at 20Z. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .