FXUS63 KIND 021054 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 654 AM EDT Wed Apr 2 2025 .KEY MESSAGES... - Severe weather mainly this evening into the early overnight - Flood Watch this evening to Sunday with 4 rounds of moderate to heavy rain and total QPF potentially as high as 6-8 inches - Wind Advisory 8AM to 1AM with wind gusts to 50 mph expected - Widespread, significant river flooding expected late week into next week. && .SHORT TERM (Today and tonight)... Issued at 303 AM EDT Wed Apr 2 2025 SYNOPTIC OVERVIEW... An upper level low will move northeast into Minnesota into tonight. Southwest flow aloft will continue across central Indiana. A potent upper level jet will be northwest of the area, with the right entrance region influencing central Indiana. At the surface, low pressure will move into Wisconsin, first bringing a warm front through the area early today, followed by a cold front tonight. Strong southwest winds aloft will pump in very high moisture for this time of year, with integrated water vapor transport values as well as precipitable water values near climatological maxima for early April. Some showers and storms will accompany the warm front this morning, especially north. More widespread convection will develop ahead of the cold front and perhaps along it as well later this afternoon and tonight. NON-THUNDERSTORM WIND THREAT... Mixing after the warm frontal passage will tap into some of the stronger winds aloft today, especially this afternoon. Wind gusts near 50 mph are possible. Sustained winds over 30 mph are likely at times as well. Will continue the Wind Advisory. SEVERE WEATHER THREAT... Parameters this morning for convection with the warm front aren't that great, so do not expect severe storms with these. The wind fields will produce strong shear across the entire area this afternoon and evening. Even with cloud cover around, the strong southwest flow will bring in warmth and moisture, increasing the instability across central Indiana. The combination of strong shear and good instability will lead to the potential for severe storms this afternoon and tonight. All modes of severe weather are possible. Straight line winds from the convection of over 70 mph are possible given the strong wind fields in place. However, forecast soundings show a cap across the area for much of the afternoon. Convection will have a hard time initiating with this in place, until better forcing arrives and the cap erodes. This will likely keep any coverage of convection low for much of the afternoon hours. Widespread convection will move in, especially after 22-23Z and continue into the night. Multiple models are showing more than 1 line of convection, with some isolated convection ahead of/in- between the lines. The solo storms may be able to tap into the shear/instability and become supercellular and produce large hail as well as tornadoes if the storms form. Otherwise, damaging straight line winds will be likely with the lines of convection, with perhaps some meso-vorticies producing tornadoes within the lines. POSSIBLE SCENARIOS FOR SEVERE... 1) The afternoon remains pretty quiet with the cap in place. Next, better forcing from the larger system will create a stronger line impacting the northern forecast area. To the south, another line would form in the better parameter space, impacting the southern forecast area. The central forecast area could see strong to severe individual storms or, on the other hand, weaker storms with the other lines dominating. 2) The cap is weaker than forecast this afternoon and individual storms develop and become severe/potentially supercellular. Lines of severe convection would then follow this evening. HEAVY RAIN/FLOODING CONCERNS... As noted above, near climatological maximum moisture will be around for the storms to work with. Multiple lines of storms could lead to heavy rain amounts. At the moment, it appears that 1.5 to 2 inches of rain is possible through 12Z Thursday across the south, with 0.75 to 1.25 inches north. HREF Local Probability Matched Means for 24 QPF show the possibility of local amounts of over 3 inches south. Thus feel the Flood Watch begin time looks good given the above potential. && .LONG TERM (Thursday through Tuesday)... Issued at 326 AM EDT Wed Apr 2 2025 ...MULTIPLE ROUNDS OF HEAVY RAIN THROUGH SUNDAY MORNING... ...SIGNIFICANT FLOODING POSSIBLE... An active and exceptionally wet pattern will continue through the weekend as a frontal boundary becomes quasi-stationary across the Ohio Valley. A highly amplified upper level pattern across the country anchored by a deep trough over the Intermountain West and a strong ridge off the southeast US coast will place the Ohio Valley within a deep southwest flow that will draw a rich fetch of moisture from both the equatorial Pacific and the Gulf. The setup in tandem with a stagnant frontal boundary and sharp baroclinic zone that will further promote strong lift and convergence is one that is historically supportive of a prolonged risk for heavy rainfall and flooding for the Ohio Valley and central Indiana. After Wednesday night, several more rounds of rain are expected through Sunday, which could bring anywhere from 4 to almost 9 inches of rainfall during that timeframe, with highest amounts expected across the south, and thus the potential for significant flooding by the weekend. The glimmer of good news is that all of this rain is expected over 4 to 5 days instead of 1 or 2, but still a concerning amount for what will quickly become a saturated ground. Models continue to lack agreement on exactly where the swath of showers and storms will set up day to day for the latter part of the week, particularly how far north storms get Thursday and Friday. Confidence grows Friday night into Saturday with better agreement that the boundary and moisture surge will shift northward into Central Indiana. With this late week surge comes the higher concern for a flooding threat. Parts of our forecast area will likely have creeks and rivers overrunning their banks as well as roads flooded out. Before trying to travel, check for road closures and NEVER drive around barricades or into flood waters. Temperatures are expected to be above normal through Saturday. The stationary front will finally move off to the east sometime during the day Sunday, after which cooler, slightly below normal temperatures, will settle in for the remainder of the forecast period. && .AVIATION (12Z TAF Issuance)... Issued at 654 AM EDT Wed Apr 2 2025 Impacts: - Convection diminishing this morning. Scattered convection this afternoon then widespread convection this evening - Southeast winds becoming strong southerly after warm front passage early this morning. Afternoon gusts near 40kt - MVFR and worse conditions possible at times and especially in thunderstorms Discussion: Mixing will bring down some of the strong winds aloft today, bringing gusts up to near 40kt. Morning convection will diminish. There is low confidence on scattered convection early afternoon, but then higher confidence on widespread convection late afternoon/early evening through the evening. && .IND WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 1 AM EDT Thursday for INZ021-028>031-035>049- 051>057-060>065-067>072. Flood Watch from this evening through Sunday morning for INZ037- 039>042-045>049-051>057-060>065-067>072. && $$ SHORT TERM...50 LONG TERM...KF AVIATION...50