205 FXUS63 KIND 090444 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1244 AM EDT Wed Jul 9 2025 .KEY MESSAGES... - Scattered thunderstorms possible tonight across the western half of central Indiana. - More storms possible on Wednesday, with best chances across southern and eastern Central Indiana. - Greatest threat for storms in the extended period is Saturday. && .MESOSCALE UPDATE... Issued at 811 PM EDT Tue Jul 8 2025 Convection associated with both the upper level wave and a surface trough from north central Illinois into southeast Missouri will continue to drift eastward over the next several hours. Preferential continued development, if any, is likely to be on the southern/southeastern flank of this loosely organized system, in the direction of the existing instability gradient, keeping these areas southwest of central Indiana. The stratiform precip area with perhaps some embedded thunder will likely make it into west central Indiana in the next hour or two, but should continue to steadily weaken as ACARS soundings and mesoanalysis indicate significant dry air in the column and minimal instability as a result - not to mention the unfavorable diurnal timing as sunset approaches. Some convective enhancement of the upper wave may be ongoing, and CAMs indicate some potential for development late tonight as this weak MCV like feature encroaches upon the area, but with minimal effective shear, this should amount to little more than a few thundershowers, perhaps with a brief heavy downpour. && .SHORT TERM (This evening through Wednesday)... Issued at 317 PM EDT Tue Jul 8 2025 Surface analysis early this afternoon 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 northern WI. GOES16 shows CU Developing across Central Indiana. More cloud cover was 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 thunderstorm complex. Showers and thunderstorms over NRN IL were continuing to diminish, while storms had developed over southern IL and western KY. High pressure over the area is expected to continue to depart this evening, allowing the development of weak and unorganized southwest flow ahead of the low over WI and its associated upper trough over the Mississippi Valley. Subsidence currently remains in place over Indiana. HRRR shows storm development expected over IL this afternoon, near a poorly defined cold front, slowly pushing east. HRRR suggests this precip should reach the Wabash valley shortly after 00Z, but weaken and dissipate as heating is lost and dry air and subsidence is encountered aloft. Thus will to to confine best pops this evening across western parts of the forecast area shortly after 00Z, but eventually trend toward just a slight pop as the frontal boundary will still be approaching and entering western Central Indiana overnight. Skies should remain at least mostly cloudy overnight as the upper trough arrives in Indiana and residual mid level clouds linger across the state. Given the expected cloud cover, lows in the upper 60s will be expected. Wednesday... Models suggest the upper trough moving through and exiting the forecast area through the mid day hours, with subsidence building into NW Indiana by mid to late afternoon and slowly expanding southeast. The weak, poorly defined surface front/trough should also exit Indiana to the east by late in the day. Time heights show good lower and mid level moisture available as this forcing is passing. Forecast soundings show marginal CAPE near 1000-1300 J/KG through the afternoon, but pwats remain quite high, over 1.90 g/kg, indicative of a very moist air mass. HRRR shows most of the frontal tsra development across eastern parts of Central Indiana on Wednesday morning, while some isolated afternoon showers/storms are shown to pop up in the wake of the front due to daytime heating alone. Confidence is low for all of these features, but there is enough of a signal here that at least some pops will be required. Best pops will be used across the south and eastern parts of the forecast area that will likely have the greatest chance to be both impacted by daytime heating and forcing from the passing upper trough and surface front. Lesser pops will be used across the rest of Central Indiana, in the wake of the front, where storm development should remain rather isolated as diurnal heating will be the main forcing mechanism amid an unfavorable area for development. With little temperature advection expected, highs in the mid to upper 80s will be expected again, && .LONG TERM (Wednesday night through Tuesday)... Issued at 317 PM EDT Tue Jul 8 2025 A somewhat active weather pattern will develop over the area through the long term, featuring multiple weak shortwaves and associated surface features bringing several chances for thunderstorms across central Indiana. The first part of the long term will see a few weak shortwaves embedded within a larger upper trough. This will help to provide enough lift and moisture for daily chances of showers and thunderstorms for the end of the week and into the weekend. Best chances for storms will be during the afternoon to evening hours each day, thanks to help from diurnal heating. At this time, severe weather is not expected although isolated heavy rain and brief strong wind gusts cannot be ruled out. Saturday has the best chance for more widespread storms, with which has the best chance of heavier rain and localized flooding within the long term as models are showing a swath of PWATs in excess of 2" moving through the region, which is above normal for this time of year. The influence of high pressure looks to bring a brief break in precipitation early next week before more troughing and shower/storm chances arrive at the end of the period. Temperatures will see highs in the mid to upper 80s most days with areas across the south potentially seeing near 90 a couple of days. Overnight lows will be in the 60s to 70s. && .AVIATION (06Z TAF Issuance)... Issued at 1244 AM EDT Wed Jul 9 2025 Impacts: - Brief MVFR visibilities near daybreak possible in fog - Scattered thunderstorms possible this afternoon, but too low probability for mention at this time Discussion: Showers continue to diminish over the northern Wabash Valley early this morning with much drier air across the region. Other than a stray light shower...expect largely dry conditions through daybreak. Patchy fog remains a possibility at the outlying terminals in the predawn hours...but the expansion of mid level clouds into the region should mitigate this threat to some degree despite ample moisture lingering near the surface. An upper wave and weak surface boundary will cross central Indiana later today and will likely spark scattered convection potentially as early as later this morning continuing into the afternoon. Overall coverage is expected to remain too low to even include PROB30s at this time. Diurnal cu will again develop into the afternoon before diminishing this evening as slightly drier air arrives in the wake of the weak frontal passage. Winds will be light through the forecast period...gradually transitioning to W/NW this evening. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Puma LONG TERM...KF AVIATION...Ryan