


Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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624 FXUS63 KIND 081633 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1233 PM 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. && .FORECAST UPDATE... Issued at 929 AM EDT Tue Jul 8 2025 Surface analysis late this morning shows weak and broad but poorly defined high pressure was stretching from Arkansas across Indiana to MI and Ontario. A weak low pressure system was found over eastern MN and western WI. GOES16 shows mostly clear skies across Central Indiana with more cloud cover found upstream over IA and MN, near the previously mentioned low pressure system. Aloft, water vapor imagery shows subsidence over Indiana but an approaching upper trough over the northern Mississippi valley contained cloud cover and moisture due to a decaying thunderstorm complex. Showers and thunderstorms over IA and IL were continuing to diminish at this diurnally unfavorable time for storm growth. This afternoon, the surface high pressure across Indiana and the region will continue to slowly drift east. The upper trough over the upper midwest will also nudge eastward toward Indiana. The forcing associated with this trough will not quite reach Indiana until tonight. Forecast soundings and time heights show a dry column through the afternoon along with convective temperatures in the upper 80s. HRRR does develop new convection late this afternoon over IL, but this fails to reach the Wabash until after 9PM. Thus another dry and warm, mostly sunny afternoon will be expected. Some CU will be expected by late afternoon as convective temperatures are approached. Overall, ongoing forecast remains in good shape and only changes will be these minor tweaks. && .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. 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 this evening 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 later this evening. Will focus highest precip chances over the northwest half of the area 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 (18Z TAF Issuance)... Issued at 1233 PM EDT Tue Jul 8 2025 Impacts: - VFR this afternoon and evening. - Scattered convection possible this evening...mainly at KHUF and KLAF - MVFR possible overnight and early Wednesday due to fog. Discussion: High pressure over Indiana will exit east this afternoon and evening. As max temps are reached today, some diurnal CU is expected to develop. Convection is expected to re-initiate over IL this afternoon and attempt to push toward the Wabash early this evening. However the HRRR suggests that as heating is lost, any showers or storms will weaken and dissipate before reaching IND or BMG. For now, we have included a VCSH mention at LAF and HUF as confidence is low. Confidence is also low for fog tonight. As the upper trough passes across Central Indiana mid level clouds is expected overnight, but surface winds are expected to be light to calm. Clouds may diminish cooling, however any evening rains would add to residual lower level moisture. Uncertainty is high on this element, so for now just a tempo of MVFR fog has been used. Rain chances may return on Wednesday afternoon as an upper trough crosses Indiana. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Puma SHORT TERM...Ryan LONG TERM...CM AVIATION...Puma