420 FXUS63 KIWX 091034 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 634 AM EDT Mon Jun 9 2025 .KEY MESSAGES... - More showers and scattered thunderstorms this afternoon into early tonight - Marginally severe storms with locally heavy rainfall are likely with damaging winds the greatest severe weather threat - Very warm Wednesday and Thursday with highs in the mid 80s && .DISCUSSION... Issued at 315 AM EDT Mon Jun 9 2025 An anomalously deep upper low was near INL (International Falls, MN) early this morning with a 5450 meter height. The surface pressure had just dipped below 1000.0 mb. This system will work in tandem with a short wave diving south on the back side of the upper low system merging with a disturbance ejecting east out of the High Plains. This combination will bring showers and scattered thunderstorms to the forecast area this afternoon into early tonight. As for chances for severe weather, instability should be marginal with max afternoon CAPEs up 500 J/Kg per GFS BUFKIT. However, the upper level flow will be quite strong with low level bulk shear (0-6 Km) reaching 60 knots. Gut feeling is there will be a similar scenario to yesterday but with wind gusts a little stronger and more numerous than yesterday. A few to several storms are likely to have wind gust between 50 and 60 mph. It looks like the most optimal time for severe storms today is between 3 PM EDT and 9 PM EDT with the combination of max heating occurrence and the cold front and the upper energy arriving and coinciding. Temperatures should reach the mid 80s Wednesday with the next chance for rain arriving Wednesday night in the form of showers and storms as more energy in the form of upper level trofs arrives. At this time, it looks like the most favorable period for thunderstorms for Wednesday through Sunday is during the diurnal favored window between 3 PM EDT and 9 PM EDT (19Z to 01Z). && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 630 AM EDT Mon Jun 9 2025 A band of rain tied to low level baroclinic zone with lead frontal boundary will remain south of the terminals early this morning. Westerly low level flow in wake of this trough has advected in a drier low level airmass into northern Indiana, with just some scattering mid level clouds early this morning. Looking upstream, a potent upper level short wave trough is tracking southeast across southern Minnesota. Vorticity advection with this feature and cooling mid/upper level temps should act to overcome the marginal moisture setup for isolated to scattered convection this afternoon. Given track of vort max and position of upper cold pocket, best chance of thunder may still be along and north of US Route 6 corridor, but both KSBN and KFWA appear to be inline for at least narrow window of scattered shower/thunderstorm potential this afternoon/early evening. Dry subcloud layer and evaporative cooling processes should pose gusty wind threat with these storms, but will hold off on inclusion of convective gusts given lingering uncertainty in convective coverage. VFR conditions should hold through this period with possible exception of brief restriction with any isolated stronger storm. Given large depth to steep low level lapse rates, synoptic sfc gusts will also be in an issue today with a potential of 25 to 30 knot southwest gusts in advance of the secondary cold front/upper trough. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...Small Craft Advisory from 1 PM this afternoon to 8 PM EDT this evening for LMZ043-046. && $$ DISCUSSION...Skipper AVIATION...Marsili