425 ACUS11 KWNS 131906 SWOMCD SPC MCD 131906 OHZ000-MIZ000-INZ000-ILZ000-131930- Mesoscale Discussion 0397 NWS Storm Prediction Center Norman OK 0206 PM CDT Mon Apr 13 2026 Areas affected...portions of northeastern Illinois into northern Indiana and extreme southern Lower Michigan Concerning...Severe potential...Watch needed soon Valid 131906Z - 131930Z Probability of Watch Issuance...95 percent SUMMARY...The severe threat is increasing, with a WW issuance impending. Severe hail appears to be the main threat, though a couple of damaging gusts are also possible. DISCUSSION...Elevated convection, which has been oscillating in intensity within a low-level WAA advection regime, has recently shown an uptick in intensity, with 1 inch diameter hail recently reported. These storms are moving over a heated airmass, with surface temperatures warming into the 80s F. Given boundary layer growth, these storms are likely rooting into the boundary layer, where 1500 J/kg MLCAPE is present. Given 30+ kts of effective bulk shear, surface-based supercell development is likely underway. The strongest storms will support a severe hail threat over the next few hours, though a damaging gust or two is possible. A tornado cannot be completely ruled out. Given the recent uptick in storm intensity, a Severe Thunderstorm Watch will be issued momentarily. ..Squitieri/Hart.. 04/13/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IWX...IND...LOT... LAT...LON 41448883 41908707 42028574 41938492 41618460 41168467 40798527 40668612 40608701 40608766 40738846 41448883 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN  484 ACUS11 KWNS 131919 SWOMCD SPC MCD 131918 SDZ000-MTZ000-WYZ000-132045- Mesoscale Discussion 0398 NWS Storm Prediction Center Norman OK 0218 PM CDT Mon Apr 13 2026 Areas affected...portions of extreme southeast Montana into extreme northeast Wyoming and far western South Dakota Concerning...Severe potential...Watch unlikely Valid 131918Z - 132045Z Probability of Watch Issuance...20 percent SUMMARY...A localized severe threat may develop through the afternoon. Severe gusts are the main threat, though a few instances of hail and perhaps a landspout tornado are also possible. DISCUSSION...Low-topped storms have recently developed near a secondary surface low and a low-amplitude mid-level impulse overspreads the northern High Plains. Ample surface heating has allowed for deep boundary layer mixing, with surface dewpoints in the 20s-40s F noted. These storms are likely high-based, and will be capable of producing a few severe gusts due to evaporative cooling within the deep/dry boundary layer. 19Z mesoanalysis depicts well over 100 J/kg 0-3 km CAPE amid very high amounts of low-level vertically oriented vorticity. Storms will likely be outflow dominant due to evaporative cooling producing extensive cold pools. However, any updrafts in this vorticity rich environment that can avoid undercutting for appreciable periods of time may support a landspout threat, as well as the potential for some hail. Given the isolated nature of the severe threat, a WW issuance is not currently anticipated. ..Squitieri/Hart.. 04/13/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR...BYZ... LAT...LON 44710575 45410551 45830459 45940316 45770230 45360190 44950183 44570207 44300281 44160388 44250521 44710575 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN  219 ACUS11 KWNS 131938 SWOMCD SPC MCD 131938 OKZ000-TXZ000-132145- Mesoscale Discussion 0399 NWS Storm Prediction Center Norman OK 0238 PM CDT Mon Apr 13 2026 Areas affected...portions of northwest Texas into central Oklahoma Concerning...Severe potential...Watch possible Valid 131938Z - 132145Z Probability of Watch Issuance...60 percent SUMMARY...Isolated to widely scattered thunderstorm development is possible along a dryline this afternoon. Any sustained storms that are able to develop will bring the potential for all severe hazards, with the primary threat large to very large hail. DISCUSSION...Latest surface observations depict a dryline extending south-southwestward across western Oklahoma and northwest Texas. An area of deepening cumulus is noted in recent visible satellite imagery across portions of the Texas Rolling Plains where convective temperatures are beginning to be reached amid strong diurnal heating and deep boundary layer mixing behind the dryline. Within the warm sector, mid-80s temperatures amid mid/upper 60s F dewpoints and steep mid-level lapse rates (per 18Z LMN special sounding) are contributing to 2000-3000 J/kg MLCAPE. While upper-level forcing is forecast to remain modest at best, 30-40 kts of effective bulk shear amid a belt of enhanced mid-level flow (40+ kts at 4-5 km AGL per regional VWPs) will support supercells capable of all hazards. The primary threat with any storms that do develop is expected to be large to very large hail to 2-3+ inches in diameter, which is supported by recent mesoanalysis that indicates ample buoyancy within the hail growth zone and SHIP values of 2+. The tornado threat remains somewhat more conditional on a storm persisting into the evening hours when a strengthening of the nocturnal low-level jet will yield increasing low-level SRH and clockwise hodograph curvature. While the timing of potential convective initiation and subsequent storm coverage remain somewhat uncertain, a watch will likely be needed should initiation appear imminent given the conditionally favorable warm sector environment. ..Chalmers/Hart.. 04/13/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TSA...FWD...OUN...SJT... LAT...LON 31590023 31890044 32320043 32949998 33669938 34289902 35339860 35939814 36329749 36409705 36339669 36019643 35239632 34189672 33509717 32699779 32109849 31679918 31549972 31590023 MOST PROBABLE PEAK TORNADO INTENSITY...100-130 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN  860 ACUS11 KWNS 131943 SWOMCD SPC MCD 131942 IAZ000-MNZ000-SDZ000-NEZ000-132115- Mesoscale Discussion 0400 NWS Storm Prediction Center Norman OK 0242 PM CDT Mon Apr 13 2026 Areas affected...portions of northeastern Nebraska into far southeastern South Dakota...extreme southwestern Minnesota...and extreme northwestern Iowa Concerning...Severe potential...Watch possible Valid 131942Z - 132115Z Probability of Watch Issuance...60 percent SUMMARY...The severe threat should generally increase north of a surface low over portions of northern NE into far southeastern SD over the next few hours. Convective trends are being monitored for the need of a WW issuance. DISCUSSION...Low 60s F surface dewpoints are pivoting around and to the north of a surface low over central NE, which is boosting MLCAPE over 2000 J/kg given 8-9 C/km mid-level lapse rates in place (per 19Z mesoanalysis and an 18Z OAX observed sounding). Agitated CU is developing along the NE/SD border, where MLCINH appears to be rapidly eroding. The OAX observed sounding shows an elongated hodograph with modest low-level curvature, and the 19Z mesoanalysis depicts over 50 kts of effective bulk shear, suggesting supercell storm modes. Occasional runs of some high-resolution guidance members have depicted the initiation of stout, long-lived supercell structures originating from this mesoscale scenario. AS MLCINH continues to erode, supercells should develop over the next few hours, accompanied by a severe hail threat. Significant severe hail is possible, with 2-3 inch stones possible, and an instance of 4+ inch diameter hail cannot be completely ruled out. Furthermore, any storms that can anchor to the warm front ahead of the surface low may be accompanied by a tornado threat. Convective trends will continue to be monitored for the need of a WW issuance. ..Squitieri/Hart.. 04/13/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...OAX...LBF... LAT...LON 42379819 41969910 41899934 41969948 42159945 42499918 42989881 43549813 43649762 43629682 43549640 43349614 43089605 42819626 42689668 42649736 42499783 42379819 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN  916 ACUS11 KWNS 131959 SWOMCD SPC MCD 131959 MNZ000-IAZ000-SDZ000-132130- Mesoscale Discussion 0401 NWS Storm Prediction Center Norman OK 0259 PM CDT Mon Apr 13 2026 Areas affected...portions of extreme southeastern South Dakota into extreme northern Iowa and southern Minnesota Concerning...Severe potential...Tornado Watch likely Valid 131959Z - 132130Z Probability of Watch Issuance...95 percent SUMMARY...The severe threat will increase along and to the north of a warm front over the next few hours. Severe wind/hail and at least a few tornadoes are possible. A couple of strong tornadoes may occur. A Tornado Watch is being issued. DISCUSSION...As widespread stratiform clouds erode in proximity to a warm front, MLCINH will continue to decrease, which is already supporting the development of a CU field between the primary warm front (where richer moisture is in place along the MN/IA border), and a differential heating boundary to the north in southern MN. Over 2000 J/kg MLCAPE and 50 kts of effective bulk shear is in place, which will support supercell structures capable of severe wind and hail. Severe hail is possible with any storms along the warm front or near the differential heating boundary, with 2+ inch hail possible. Tornadoes will also be possible with supercells anchoring to the warm front. Should a more dominant, discrete supercell sustain along the warm front, strong tornadoes will become possible. A Tornado Watch will be issued soon. ..Squitieri/Hart.. 04/13/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ARX...MPX...DMX...FSD... LAT...LON 43929685 44459550 44789417 44819352 44659307 44239276 43749272 43409307 43269386 43309488 43409583 43489621 43619666 43929685 MOST PROBABLE PEAK TORNADO INTENSITY...120-150 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN