FXUS63 KIND 151318 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 918 AM EDT Wed Apr 15 2026 .KEY MESSAGES... - Active pattern this week with near daily chances for showers and storms. Friday likely to be the driest day of the week. - A few rounds of storms expected this afternoon into tonight across Central and North Central Indiana. A few storms may be severe with damaging winds as the main threat. - Near record warm temperatures expected through Saturday with multiple days in the 80s and lows in the 60s. - Much cooler Sunday into early next week with the potential for frost. && .FORECAST UPDATE... Issued at 917 AM EDT Wed Apr 15 2026 As of mid-morning, temperatures have begun a slow rise with most locations having risen into the low 70s. Showers and storms remain west of the forecast area, mainly across western Illinois with a subtle boundary across the northern half of the forecast area where convection from yesterday moved through. An MCV is currently moving across central Illinois which may clip the northwestern counties early this afternoon, especially if it begins to turn right to tap into the boundary. Overall forecast thoughts generally match the ongoing forecast with the storm threat gradually ramping up after 17Z in the northwest with damaging winds being the primary threat due to the generally poor mid and upper level lapse rates. Other than trimming back the morning POPs to align better wit the current dry conditions, no changes were made to the forecast with the main focus through the remainder of the day being focused on the increasing threat for storms. && .DISCUSSION (Today through Tuesday)... Issued at 319 AM EDT Wed Apr 15 2026 An active weather pattern continues for the region this week with multiple rounds of showers and thunderstorms forecast to move through Central Indiana. Nearly the same synoptic set up is over the Great Lakes and Midwest as the past several days as a strong southwesterly baroclinc zone has set up from the Plains into the Great Lakes. This semi-blocking pattern will remain in place through the week with the most active period for Central Indiana tomorrow afternoon through early Thursday then again on Saturday. The pattern features a modest 80-90 kt southwesterly upper jet extending from West Texas to the Great Lakes with several embedded shortwaves. Underneath the baroclinic zone, these embedded shortwaves have kept an elongated surface low/boundary from the Texas Panhandle through Wisconsin, placing Central Indiana well within the overall warm sector. A strong nocturnal low level jet (LLJ) redevelops each night over Indiana, feeding the multiple complexes of storms riding around the periphery of the overall system. Based on where Indiana is located within the warm sector, the best forcing for ascent and storm complexes remains closer to the synoptic features to the north and west. However as these overnight MCSs die, their leftover outflow boundaries sag southward into Central Indiana. This exact scenario occurred yesterday with afternoon storms developing along these remnant boundaries. CAMs guidance does not do well in these weakly forced set ups with remnant outflow boundaries; therefore, much of the short term forecast will be based off persistence, observations, and how everything evolves upstream. The short term forecast will be lower confidence than usual regarding exact placement and timing of waves of convective development this afternoon into Thursday. But high confidence remains in the overall pattern and associated thunderstorm threats. Today and tonight... Latest satellite imagery shows a large MCS over Michigan and far Northern Indiana currently, progressing east along the warm front, while an additional complex of storms develops over Iowa and Northern Illinois closer to the elongated surface low and cold front. An upper wave along the front range of the Rockies will work to shift this entire system and baroclinic zone eastward over the next 24 hours, placing the area of best forcing for ascent and the storm track closer to Indiana with several rounds of storms expected to impact the region. Mainly dry conditions should persist for Central Indiana for the rest of the morning and early afternoon hours as dry air and subsidence on the south side of these MCSs keep convection out of the area. However for later this afternoon and evening, keeping an eye on what happens with the remnant outflow boundary from the current MCS in Northern Indiana and how it interacts with a mid level shortwave in the Arklatex region moving northeast toward the Ohio Valley. This wave should provide the necessary forcing for convection development this afternoon in Illinois and Indiana along remnant boundaries in the warm sector. Unfortunately, it is difficult to determine where exactly these boundaries will set up at the moment. Current thinking is that areas along and north of I-70 have the best storm threat after 17z this afternoon. The environment will be more than conducive for severe weather as elongated hodographs within an unstable airmass suggest. Weak mid and upper lapse rates may limit the overall hail threat today, but high DCAPE values, and steep low level lapse rates with 30-40 kts of effective shear should be enough to support organized severe storms with a damaging wind threat with isolated tornadoes. Expect multiple rounds of convection going into tonight as the overall storm system begins to shift east. The threat for severe weather during the overnight hours should be more synoptically driven as surface wave moves northeast into the Great Lakes with a trailing front in Indiana. The increasing low level jet overhead ahead of the approaching system will work to increase overnight rounds of storms to the west/southwest which move into Central Indiana. The environment overnight will also be conducive for surface based severe weather within such a moist and unstable environment with increasing wind shear. The main threat going into tonight should still be damaging winds as largely unidirectional flow and speed shear support upscale growth of complexes into lines and bowing segments. Thursday through This Weekend... Ridging briefly builds in on Thursday as the overall system shifts eastward...however another broad southwesterly baroclinic zone quickly sets up over the Plains again with surface cyclogenesis occurring over the upper Midwest. This will place Indiana and much of the region back into a hot and humid pattern within the warm sector of the developing low. Expect a drying trend Thursday as ridging builds in. Little to no cold air on the backside of the front means another above average day with highs well into the 70s, but with slightly lower humidity values due to subsidence under the ridge and dry air mixing down. As a strong warm sector becomes established on Friday over the Plains and Midwest, Indiana will have one full day of dry and very warm weather before the next threat for storms arrives on Saturday. Models show that the surface low with this system will be unphased and tracking ahead of its upper component. This will potentially make Saturday's system more diurnally driven rather than synoptically forced. At this time, strong deep layer flow will be parallel to the cold front which could be enough to form a line of storms with damaging winds being the main concern. Outside of storms, stronger gusts are likely Saturday and into Sunday since the elevated portion of the system will be lagging behind. General gusts Saturday could reach as high as 35-40 mph and around 25 mph on Sunday. There are still some differences on when the associated cold front would exit, but likely sometime late Saturday into the overnight hours, behind which cooler and below normal temperatures will return at least for the first couple of days of the new week. Lows Monday morning could be approaching near freezing to mid-30s. Surface high pressure behind the front looks to track over the Ohio Valley, allowing for dry weather for the start of the new week as well. && .AVIATION (12Z TAF Issuance)... Issued at 642 AM EDT Wed Apr 15 2026 Impacts: - Mainly SSW winds through the TAF period, gusting to 17-28KT - Non-zero chances of additional convection this evening - Multiple rounds of convection 17z Wed - 12z Thu Discussion: Mainly VFR conditions will prevail across central Indiana this evening as satellite imagery shows most of the convective activity in the region well to the west or north. The region remains well within the warm sector of an area of low pressure to the northwest. Waves of energy within the SW flow aloft interacting with leftover boundaries will likely be the focus for thunderstorm development this afternoon into tonight. Mainly VFR cigs and vis outside of storms for the majority of the period. After 17z, widely scatter storms should begin forming along leftover boundaries. Low confidence in exactly where these boundaries set up, however thinking the set up and evolution will be very similar to Tuesday where the greatest threat is along and north of I-70. Kept Prob30 groups for TSRA after 17z at KLAF, KIND, and KHUF where the greatest threat is. Will be able to fine tune exact timing in later forecast issuances once boundaries set up. Brief periods of MVFR or worse conditions with erratic wind speeds and directions under any storm. With numerous waves of showers and storms expected to move through the area, keeping the threat for storms through the end of the TAF period. Outside of storms, breezy, south-southwest flow to prevail through the period, with slight changes in direction possible, especially near any showers. Took out any mention of LLWS overnight through the early morning hours as the boundary layer is remaining well mixed according to obs and local ACARS soundings. Wind gusts of 15-25 kts should prevail through the period. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...White AVIATION...CM DISCUSSION...CM