####018007993#### FXUS63 KIND 160422 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1222 AM EDT Fri May 16 2025 .KEY MESSAGES... - Isolated to scattered thunderstorms this evening with the potential for severe weather - Higher-end threat for severe weather tomorrow evening, especially across southern Indiana - High temperatures in the upper 80s again tomorrow - Cooler and quiet for the weekend, additional precipitation again next week && .MESOSCALE UPDATE... Issued at 900 PM EDT Thu May 15 2025 Robust linear convection has become well organized along the dryline across central Illinois this evening as individual cells have been proficient hail and wind producers so far. The line is weaker to the south of KSPI owing to the lingering cap but the southern extension which now goes all the way to the south of KSTL is something that the bulk of the CAMs did not catch over the last several hours. Confidence is growing in the convective line maintaining itself into the northwest half of the forecast area by late evening/midnight with the primary area of concern across the northern Wabash Valley which is in the direct path of the most intense portion of the line near KDEC and west of KCMI. How far south the line extends into the forecast area and the intensity of those storms still remains a bit uncertain as convective inhibition is expected to increase into the overnight and the lingering cap may continue to limit overall intensity levels. That being said...abundant instability remains above the cap and strong westerly BL shear should serve to maintain storms for the next few hours. && .SHORT TERM (This evening through Tonight)... Issued at 204 PM EDT Thu May 15 2025 Rest of Today and Tonight. Diurnally driven cu continues to expand in coverage across central Indiana with temperatures in the low 80s across the state. Dew points continue to rise with little mixing so far. Expectations going through the rest of the afternoon remain the same with a continual expansion of cu while dew points begin to fall towards the middle of the afternoon once the wind gusts become more frequent and the boundary layer steepens to around 4kft. The threat for 90 degree temperatures continue to look low for all but the far western counties where rain didn't fall as widespread yesterday. Latest ACARs soundings show the cap is well in place but a bit higher up than models have forecast with the strongest portions of the cap from 800mb to 700mb. A plume of even warmer aloft is moving in from the southwest which will further strengthen the cap through 23Z with models showing convective initiation on the western edge of the warmer air across Illinois towards 23Z. Forecast remains on track for the convective threat late today into tonight with better model agreement in scenario #2 of the previous forecast discussions where convection initiates across Illinois towards 23Z to 01Z and moves into central Indiana but doesn't strongly organize. There is a potential that the convection remains elevated above the gradually eroding cap with hail being the primary threat. The primary timeframe of concern for central Indiana will be from 00Z to 04Z with confidence highest across the far western and northern portions of the forecast area. Confidence is lower towards the Indianapolis area as there is a fairly low potential that storms will have enough time with high instability to develop a mature cold pool which would help them propagate into an increasingly less favorable thermodynamic atmosphere. There could be a few lingering storms across the southern portions of the area during the second half of the overnight, but chances look minimal. The residual humid airmass will keep temperatures very mild through the night with overnight lows only falling into the mid to upper 60s with the potential for some sites to see lows near 70. Skies will gradually begin to clear after midnight with gusts falling off after 03Z. && .LONG TERM (Friday through Thursday)... Issued at 204 PM EDT Thu May 15 2025 Friday and Friday Night. Another round of severe weather is expected for late Friday into the early overnight hours with much higher confidence in weather impacts for central Indiana. Another surface low will be tracking across the Midwest with strong moisture advection ahead of the low as the LLJ ramps up. 40-50kts of effective bulk shear will combine with nearly 4000 J/kg of ML CAPE with a much weaker cap to create a favorable environment for the development of severe storms. All severe weather types will be on the table with damaging winds the most likely threat as models continue to trend more towards an organized complex of storms vs discrete supercells. Highest confidence in timing will be from 6PM to 10 PM with the greatest threat for severe weather across the southern counties where most models show the progression of a storm complex. If storms remain discrete, which is not the most likely outcome, there will be a threat for higher-end tornadoes with STP values maxing out between 8 and 12 at times. Saturday Through Monday. Broad ridging across the Central US states will then dominate the weather pattern for the first half of the weekend with some residual near surface pressure gradients creating an environment favorable for wind gusts to around 25 mph during the afternoon hours on Saturday. With the surface flow now westerly, dew points will be much more comfortable with highs in the low to mid 70s. A weak upper level wave will move through the Tennessee Valley late Sunday into Monday but other than some increased clouds, no impacts expected for the forecast area. Tuesday Through Thursday. The pattern then looks to become much more active during the middle to latter portions of the week as a warm front associated with the late weekend system begins to move northward and interacts with forcing from another low pressure system. Models are struggling to resolve the details and strength of this upper level low, but there is fairly high confidence in a multi-day heavy rain threat for the Ohio Valley as early as Tuesday but more likely Wednesday into Thursday. Models are all over the place with QPF, but there is a decent threat for at least 1-2 inches over the course of the event. Rain chances then look low for the holiday weekend with broad northwesterly flow and mild temperatures in the 70s. && .AVIATION (06Z TAF Issuance)... Issued at 1221 AM EDT Fri May 16 2025 Impacts: - VFR conditions for much of the period. - MVFR to IFR conditions expected on late this afternoon and early evening with Thunderstorms - High confidence for afternoon and evening Thunderstorms, possibly severe. Discussion: Another active weather day is in store for Central Indiana. Strong low pressure over the upper midwest will provide SW winds and today and keep the TAF sites within the warm sector, bathed in warm and humid air. Strong SW flow aloft today along with a moist and unstable column will lead to thunderstorm development this afternoon. HRRR brings an area of thunderstorms across Indiana during the 21Z-01Z time frame. Have used a VCTS window to account for this. Some gusts of 40-50 knts will be possible due to the strong flow aloft. During this window, MVFR to IFR Conditions will be expected with the passage of storms. VFR should return in the wake of the storms as high pressure begins to build into the Ohio Valley. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...White LONG TERM...White AVIATION...Puma