752 FXUS63 KIND 270452 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1252 AM EDT Sun Jul 27 2025 .KEY MESSAGES... - Dangerous heat continues into early next week with additional days of greater than 100 degree heat indices likely, especially Monday through Wednesday - Periodic showers and storms through the weekend with isolated flooding and strong winds - More widespread thunderstorms expected for the middle of next week && .FORECAST UPDATE... Issued at 952 PM EDT Sat Jul 26 2025 No major changes needed to the forecast with this update. Rain and thunderstorms are now confined primarily across our northern tier of counties. The heaviest storms, near Muncie, have prompted issuance of a Flash Flood Warning as reports of high water have come in along with a measured rate of 3.75 inches per hour. Rain has ended in the Muncie area, and will end across Randolph County in the next hour or so. Additional storms are possible, especially across the north and northwestern portions of the area. These locations are nearest to a subtle boundary and vort max which may provide enough forcing to over come nocturnal stabilization and allow for the formation of a few updrafts. Widespread activity is not expected. Localized flooding is the primary hazard overnight. && .SHORT TERM (This Evening through Sunday)... Issued at 302 PM EDT Sat Jul 26 2025 Scattered convection had hit an earlier peak in coverage but has dwindled down locally since 1730Z. One factor that appears to be aiding this is a small area of subsidence first noted on the Day Cloud Phase satellite imagery extending from the Indy metro southwest back into Owen County. Despite the increased cu coverage...18Z temperatures were again in the upper 80s and lower 90s with peak heat indices pushing the 105 degree level across the southern half of the forecast area. The stagnant pattern of late continues this afternoon and will do so through the short term. A remnant outflow boundary from earlier served as one of the initial focal points for convective development in addition to the unstable airmass present. As mentioned above however...subtle subsidence in the wake of a more pronounced area of convection now near KMIE has led to a decrease in coverage for the time being. This is temporary and as additional storms across eastern Illinois press east into the late afternoon... potential for outflow boundaries and an increase in instability will likely see an uptick in scattered coverage that will extend into early evening. These storms will largely remain subsevere with torrential rainfall and lightning as the primary hazards...but cannot rule out stronger winds with any collapsing downdrafts. Focus then shifts to convection currently becoming better organized over western Illinois. Hi-res guidance has maintained a steady signal in tracking these storms into the Wabash Valley later this evening and perhaps further east across the northern half of the forecast area before diminishing overnight with a subtle increase in 850mb flow . There is a nonzero risk for damaging winds later this evening focused mainly over the northern Wabash Valley and will need to monitor. The greater impact from the convection though is likely to play a role in how convective development unfolds on Sunday as a remnant outflow boundary from the storms is poised to set up somewhere across the forecast area. Current indications at the moment are that this will be in the vicinity of the I-70 corridor and could aid in storms developing quickly by early afternoon and potentially with greater coverage than what we have seen today. Westerly 850mb flow would support sluggish movement to storms with a backbuilding component adding to the PWATs in excess of 2 inches that strongly suggest torrential rainfall and localized flooding as front and center concerns again. Model soundings show gusty winds with collapsing downdrafts as another threat as well. Have elected to let the Heat Advisory across the southern half of the forecast area go ahead and expire at 00Z this evening with no extension into Sunday. Peak heat indices will be below criteria though potential is there for some locations across southern portions of central Indiana to make it into the low 100s. The combination of expected convective and cloud coverage however lowers confidence on more widespread advisory level heat indices being met. With the expansion of upper ridging for Monday and Tuesday a return to heat headlines will likely be needed. This will be discussed further in the Long Term section below. Temps...another night with lows int he mid to upper 70s is expected for tonight. Highs Sunday are likely to be a couple degrees lower than Friday and today owing to the expectation of increased coverage of convection and clouds. Upper 80s to around 90 are expected. && .LONG TERM (Sunday Night through Saturday)... Issued at 302 PM EDT Sat Jul 26 2025 The deep upper level ridging will flex northward to begin the workweek with the core of the ridge settling across the Missouri and mid Mississippi Valleys by Tuesday. This will cause a renewed surge of hot and exceptionally humid conditions through the first part of the week while limiting convection to diurnally driven isolated activity. A strong upper level low will dive southeast from James Bay into the Canadian Maritimes during the second half of the week forcing a retrograde to the ridge back into the High Plains. Ultimately this will aid in sending a cold front through the Ohio Valley by Thursday night with increased convective threats Wednesday and Thursday...but more importantly will bring an end to this stretch of heat and humidity with a dry and pleasant airmass poised to settle in to open August. Sunday Night Through Thursday Rising mid level heights as the ridge builds north will lead to the reestablishment of a cap while deeper forcing and the remnant frontal boundary shift well north into the Great Lakes. Isolated diurnal convection will be a possibility focused during the afternoon and evening Monday and possibly Tuesday but the presence of the cap and warmer air aloft will mitigate more substantial coverage. Storms will produce torrential rainfall and locally damaging winds from collapsing downbursts cannot be ruled out with stronger cells. As the ridging begins to flatten and retrograde by midweek...a cold front to the north will steadily drop south into the region. While some timing differences remain within the extended model guidance... a more pronounced threat for convection and possibly a more organized risk for severe weather will impact the region first Wednesday afternoon and night across the northern half of the forecast area gradually transitioning south Thursday. Damaging winds are again likely to be the primary concern based on model soundings with torrential rainfall and localized flooding as well with PWATs at or just above 2 inches pooling immediately ahead of the front. Additional heat headlines are virtually a necessity for Monday and Tuesday as peak heat indices will be in the 105 to 110 degree range. May need headlines for part of the area Wednesday as well. For now will be messaging heavily via the HWO and social media with expectation of issuance of new headlines by Sunday afternoon at the latest. Thursday Night through Saturday Lingering storms are possible into early Friday but the frontal boundary should clear the Ohio River and continue south away from the region on Friday. As mentioned above...the passage of the boundary will take the oppressive airmass that has been over the region since earlier this week with it...replacing with a cooler...drier and much more pleasant airmass as low level flow transitions to northerly as large high pressure settles across the Great Lakes. There is growing confidence in temperatures likely to be the coolest we have experienced over much of the area since the second week of June with upper 70s and lower 80s expected. Lows may drop into the mid and upper 50s as well for Friday and Saturday mornings. For reference...Indianapolis has not seen a low temperature below 60 degrees since June 11. To put it mildly... we will be opening on August on an absolutely spectacular note. Return flow as the high moves east by early in the first week of August will bring temperatures back to near normal levels in the 80s with the potential for an increase in scattered convection as well. && .AVIATION (06Z TAF Issuance)... Issued at 1252 AM EDT Sun Jul 27 2025 Impacts: - Low chances and low confidence for TSRA development overnight. - Scattered convection this afternoon and evening, dissipating 01Z- 03Z Discussion: Again, very limited change in the overall air mass and weather situation across Central Indiana. Early morning convection found over Illinois is expected to drift east, but weaken upon approach. Confidence is low at the moment if these will impact Central Indiana. As we have seen the past few days, daily diurnal heating will lead to thunderstorm development across Central Indiana mainly during the afternoon and evening hours. Little overall change remains within the column, as it continues to show steep lapse rates, abundant CAPE and high pwats. Confidence is high for more showers and storms today, but confidence is low for specific timing and locations. Thus a large window of prob30 has been used for now. Any TSRA that does strike a TAF site may produce brief MVFR to IFR conditions. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Eckhoff SHORT TERM...Ryan LONG TERM...Ryan AVIATION...Puma