399 FXUS63 KIND 080529 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 129 AM EDT Sun Jun 8 2025 .KEY MESSAGES... - Showers and thunderstorms likely this evening into tonight - Locally heavy rainfall and flash flooding possible tonight - Cooler than normal with periodic rain early next week - Warming trend midweek && .FORECAST UPDATE... Issued at 947 PM EDT Sat Jun 7 2025 The forecast is mostly on track. I have toned down the TS chances significantly to chance/slight chance owing to marginal instability, extremely poor mid level lapse rates, and lack of any lightning in the area despite strong reflectivity cores. PoPs were raised to over 90% generally along and north of I-70 through the early morning hours. Confidence is high that as mid level disturbance moves out of IL, low level forcing/convergence will continue to strengthen as surface low approaches and moves across this part of the forecast area overnight. Already some areas of west-central Indiana have received 2-3 inches of rainfall. Definitely a possibility that similar localized totals in that same range will occur for areas north of I-70 leading to localized flooding potential. Expectation is that many areas north of I-70 will receive between 1 and 1.5 inches by 12Z. Precip should gradually end from west to east after 06Z, although some slight chance of showers could remain for an hour or two beyond 12Z in the far eastern portion. Ceilings will fall later tonight and patchy fog is possible, but widespread low cloud cover precludes any mention in the forecast. && .SHORT TERM (This evening through Sunday)... Issued at 303 PM EDT Sat Jun 7 2025 Northeasterly flow earlier today brought a round of wildfire smoke which lead to hazy skies and reduced visibility. The haze has thinned some as winds are beginning to take on a southerly component ahead of a developing low to our west. Any thicker haze should be confined to our northeast this afternoon. The aforementioned low developing to our west is being driven by a weak mid to upper-level wave, which is in the process of gradually de-amplifying. Guidance is mixed on how strong of a surface low makes it to our area, with the higher-resoluation / CAM guidance generally showing a weaker solution versus the global models showing a stronger solution. Regardless, abundant cloud cover along with scattered showers and thunderstorms is expected this afternoon into tonight. Model soundings show tall and skinny CAPE profiles, moist adiabatic lapse rates through the column, and weak shear (under 30 knots). Severe weather is not expected, but with high freezing levels and a very moist column rainfall production could be quite efficient. A flash flooding threat may materialize overnight as convection could be slow-moving and/or repetitive. The best timing of heavy rain looks to be after 00z this evening and into the overnight. Spatially it is a bit less certain, as convection looks to be quite random and slow-moving. However, if we end up with a stronger low there could be a bit more forcing available to help concentrate convection. Mid-level frontogenetical forcing associated with the 700mb low center may be the most likely spot for this. Based on latest model trends, the most likely path of the mid-level low looks to be across the northern half of our CWA. Temperatures shouldn`t drop too much tonight with thick cloud cover. A diurnal swing of only 10 degrees appears likely, which places lows only into the mid 60s by Sunday morning. Low clouds are expected to decrease during the day Sunday as today`s low exits off to the east. Temperatures should rebound into the mid to upper 70s except over our northeast where low clouds could persist a bit longer. && .LONG TERM (Sunday night through Saturday)... Issued at 303 PM EDT Sat Jun 7 2025 Strong vorticity advection on the SE side of an upper level trough will aid in southward progression, eventually putting the trough axis just north of Indiana Late Sunday into Monday. Confluence along the leading edge of the 850-500mb low will aid in a narrow corridor of moisture convergence and lift. Prior to the corridors arrival, the antecedent airmass will likely be rather dry on Sunday, of which should keep precipitation from falling until after 00Z Monday. Lapse rates within this confluence zone on Sunday night are marginal (just above 6 C/km), of which will limit instability and updraft growth. This should lead to scattered showers with isolated thunderstorms, all of which will likely remain sub-severe. Latest trends have been delaying the boundary passage until additional low level pressure depletion during the day on Monday. If this does occur, another round of thunderstorms is possible Monday afternoon and evening, this time with some severe risk given a locally enhanced area of shear. There is still a lot of uncertainty for Monday`s synoptic pattern, but this should be monitored closely given the potential severe threat. After this frontal passage, shortwave ridging will move into central Indiana, leading to a dry period Monday night through Wednesday next week. Temperatures will moderate but likely remain near seasonal without strong WAA or upper level ridging. Later in the week, combating dynamics will likely lead to an unorganized upper level pattern, with a tendency towards broad upper level riding, but with a developing mid level low. The current expectation is for this to lead to hot, humid weather, but with temperatures subdued slightly due to increases in cloud cover and precipitation. There is still high uncertainty on any rain timing, but the general pattern should support periods of rain Thursday through the weekend. Expect highs to be above seasonal averages, likely in the low to mid 80s with elevated dew points. && .AVIATION (06Z TAF Issuance)... Issued at 129 AM EDT Sun Jun 8 2025 Impacts: - Widespread showers ending early in the period. - Conditions will deteriorate to IFR overnight, returning to VFR early Sunday afternoon - Additional showers and storms arrive after 00Z Monday Discussion: Rain coverage will diminish overnight, but as it does, ceilings will settle in the IFR category. Visibility will stabilize in the MVFR range with fog overnight. Fog will mix out by 14Z, but VFR ceilings won`t return until early Sunday afternoon. Confidence on the specifics of this transition is medium. Rain returns Sunday evening, with MVFR conditions possible in the rain. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Crosbie SHORT TERM...Eckhoff LONG TERM...Updike AVIATION...50