022 FXUS63 KIND 080705 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 305 AM EDT Tue Jul 8 2025 .KEY MESSAGES... - Warm...dry and less humid today - Scattered thunderstorms possible tonight across the western half of central Indiana - Greatest threat for storms in the extended are Wednesday and Saturday. - Localized flooding threat on Wednesday with slow moving storms. && .SHORT TERM (Today and Tonight)... Issued at 305 AM EDT Tue Jul 8 2025 Skies were mainly clear early this morning as weak high pressure had built in as a remnant frontal boundary had slid south of the Ohio River. Patchy fog was developing across the forecast area currently as well. Slightly drier air had advected into the region and temperatures were cooler as a result in the 60s at 06Z. The aforementioned high pressure will maintain its influence across central Indiana for a good portion of the day as it drifts into the eastern Great Lakes. A stronger upper wave will approach the region this evening into the overnight and bring an increasing threat for scattered convection into the western half of the forecast area focused especially during the predawn hours Wednesday. The initial challenge is on continued fog development over the next few hours as light N/NW flow interacts with damp ground conditions from rain the last few days and a lingering shallow layer of moisture within the boundary layer. Coverage should remain scattered through daybreak but there will likely be spots with locally dense fog especially across the southeast half of the forecast area where dewpoints remain higher. Will continue to monitor over the next few hours. Much of the day will be quiet with abundant sunshine and light winds that will eventually return to a S/SW direction. Model soundings remain suggestive of a diurnal cu field for the afternoon but the presence of a capping inversion will limit vertical extent to cu at least through late afternoon. By this evening...slightly better instability will spread into the Wabash Valley and may generate isolated convection into the evening. The focus however will be back across the Missouri and mid Mississippi Valleys in closer proximity to the upper level wave and a subtle surface low. More widespread convection will develop late today in the vicinity of this feature spreading east into tonight. There is low potential for a brief wind threat with these storms as they approach but the development of the nocturnal inversion will support increasingly elevated convection as the storms arrive into the Wabash Valley in a weakened state after midnight and through daybreak Wednesday. Will focus highest precip chances over the northwest half of the area late tonight...with brief heavy rainfall again being the primary concern from convection. Temps...low level thermals support highs into the mid and upper 80s this afternoon but dewpoints are likely to hold in the low to mid 60s through late day which will keep comfortable humidity levels in play. Moisture will increase tonight with the approaching upper level wave with lows reverting back to the upper 60s and lower 70s in response. && .LONG TERM (Wednesday through Monday)... Issued at 305 AM EDT Tue Jul 8 2025 A progressive weather pattern develops over much of the country through next week featuring several weak shortwaves and associated surface features bringing several chances for thunderstorms across Central Indiana. A digging trough and associated shortwave dive southeastward from the Dakotas and into the Great Lakes Tuesday night bringing the next chance for showers and storms to the region. The surface feature associated with this synoptic system is fairly weak and diffuse, so expect mid range models to struggle with the evolution of the surface pattern and placement of areas of greatest convective activity. This will likely be a set up where micro to mesoscale features develop Tuesday in the Central Plains then propagate eastward into the state along and just ahead of the upper trough axis. Latest guidance shows upstream convective activity struggling to make it eastward into Indiana Wednesday morning. Depending on the evolution of morning convection, the placement of the weak surface feature, and how quickly the environment can recover Wednesday afternoon, there may be another round of storms during peak heating of the day and into the evening hours. With how weak forcing is within a warm, humid, and very unstable environment, expect slower moving storms to develop along micro to mesoscale boundaries, further enhanced by outflow boundaries of dying storms. This pattern tends to lead to slow moving storms with a higher potential for localized flash flooding in areas that see repeated rounds of storms. Severe weather threat is fairly low, however a strong wind gust is certainly possible in any storm that collapses. The upper trough and associated surface wave exit to the east by Wednesday night, leaving lee side subsidence building across Indiana into Thursday as a subtle upper ridge axis builds across the upper midwest. Expect a brief drying trend Wednesday evening into the first half of Friday as subsidence under the ridge prevents convective activity from developing. A warm and fairly humid airmass will still remain in place at the surface with highs in the mid 80s to near 90. A better threat for more widespread thunderstorms and potentially severe weather arrives Friday into Saturday as a much deeper trough and stronger front approach from the west. Lower confidence exists on timing and finer details of this system being so far out in time. At the moment, a stronger low level jet overhead combined with a moist, unstable surface airmass, and better forcing may lead to a set up more conducive for organized convective activity and a few severe storms. Timing is still uncertain as some guidance brings precipitation in by Friday afternoon, while others slow the system down and bring storms in on Saturday. For now, keeping Chance PoPs for Friday with a better chance for storms earlier on Saturday. Will fine tune the precipitation forecast and timing as confidence increases. High pressure pressure and subtle ridging post front should lead to a drier end to the weekend and beginning of next week with temperatures near normal for this time of year. Overall, the days to watch in the extended are Wednesday and Saturday for the most active, and potentially impactful weather conditions. && .AVIATION (06Z TAF Issuance)... Issued at 1226 AM EDT Tue Jul 8 2025 Impacts: - Widespread MVFR conditions with occasional IFR in fog from the predawn hours through daybreak Discussion: With clearing skies, N/NW winds expected to weaken and perhaps go calm in spots, wet antecedent soils, and dewpoints remaining largely in the 60s even in the wake of a frontal passage, fog is expected to develop over the nest few hours and persist through daybreak. Guidance suggests widespread MVFR with some periods of IFR, and have taken this approach at all sites, with 3-4SM prevailing and TEMPO 1- 2SM, along with a BCFG mention at all sites, as sites with lightest winds could easily drop into LIFR or worse at least briefly. Once fog mixes out, VFR conditions are expected with winds below 10kt out of the S/SW on Tuesday. Diurnal cu will likely develop for the afternoon and early evening before diminishing. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Ryan LONG TERM...CM AVIATION...Nield/Ryan