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998 FXUS63 KIWX 120819 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 419 AM EDT Thu Jun 12 2025 .KEY MESSAGES... - Partly to mostly cloudy skies today with highs in the 80s. There are low chances for showers and thunderstorms late this afternoon and evening, mainly in Michigan and near Lake Michigan in northwest Indiana. Lows tonight will fall into the 60s. - Chances for showers and thunderstorms persist on and off through next week, with the best chances late Friday night into Saturday. Highs will be in the upper 70s and 80s. && .DISCUSSION... Issued at 417 AM EDT Thu Jun 12 2025 Tricky forecast for late this afternoon into Friday, with models all over the place in terms of where/when/how much precipitation we get thanks to fairly zonal flow aloft. At the moment we have a weak surface low over southern Lake Michigan with a stationary boundary draped from Davenport, IA through South Haven, MI and into Detroit, MI. All overnight convection has stayed well north of the area, despite some cloud debris (mainly high clouds, some mid level). All models are in agreement as to the initially dry conditions (through about 21z) given the slight ridging aloft and fairly dry air in place. However, discrepancies arise in the 21-03z time frame, with the HRRR and some of the CAMS generating showers/storms as a shortwave approaches aloft. As the stationary boundary shifts slightly southward this afternoon (models disagree on if and how much it shifts), winds become more N-NW near the lakeshore and more E-NE generally north of US 30. Flow south of the boundary remains southerly. I suspect that as this occurs, we'll see some enhancement to the convergence with flow of lakes Michigan and Erie, which seems to be where the showers/storms are generated around the 21-00z time frame, lingering through about 3z. It's difficult to say if this will occur given dry air around and the potentially strong cap in place initially (NAM has nothing)-but felt 20-25 percent chances were reasonable during this time frame. Depending on how much of this cloud cover sticks around, we'll probably see highs climb into the mid-upper 80s for some locations (warmest along and south of US 30 and west of US 31). The lake Michigan shoreline, Hillsdale Co, MI and Fulton Co, OH may only see highs in the low to mid 80s. As far as tonight goes, lows will be in the 60s with increasing clouds. POPS late tonight into Friday are still low to medium confidence. Models are all over the place in terms of location and timing, and the extent of coverage. Have generally 30 to 60 percent chances max on Friday, with the higher chances in the southwest [generally south of US 30 and west of I 69]. Delayed start time tonight in this area until 9-12z, then have chances increasing through the afternoon as moisture transport increases (particularly along the stationary front which is theoretically draped from Stark Co, IN to Allen Co, OH at that point). Highs Friday will be in the 70s and low 80s. Meanwhile, a cut off low over the central plains moves into MO by 00z Sat-then shifts eastward through Saturday night, which will increase our potential for showers and a few storms late Friday night into Saturday. Have the highest pops (30-84%, highest along and south of US 24-particularly east of IN SR-15) during this period- shifting eastward through Sunday morning. The upper level low begins to wash out by Sunday into Sunday night, so confidence decreases after that in regards to how much forcing we'll have around. Kept 20- 50 percent chances Sunday, but suspect we may be able to lower those if the system drifts southeastward faster than what is currently forecasted. Highs Saturday into Sunday will be in the 70s and low 80s. A lull in chances is expected Sunday night into Monday, with another shortwave moving in from the west that crosses through the area by about Tuesday evening. Confidence is lower in this period given so much initial uncertainty-but have 20-40 percent pops for now-which is reasonable. Highs will make their way into the mid 80s once again by Tuesday. Another more potent wave builds through at some point Wed-Thur, but models disagree on the exact timing. For example-the ECMWF is more progressive and bringing a broader trough in Wed-Thu; and the GFS by comparison keeps a stronger ridge initially in place and then brings a weaker trough through by Thu-Fri. For now kept consensus pops of 30-60 percent in (highest Wed afternoon), with highs in the mid to upper 80s. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1228 AM EDT Thu Jun 12 2025 The bottom line as far as storms - it will be very difficult to overcome the combination of dry air entrainment, stable mid level lapse rates and a capping inversion at the base of the subsidence. The dynamics with a very weak front should not be enough to trigger storms. Have kept storms out of TAFs given these parameters. Winds should stay south to southwest at 3-8 knots with very weak synoptic flow. Some haze or smoke may be present, but at this time the concentration appears low and does not appear to be operationally significant. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...MCD AVIATION...Skipper