


Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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375 FXUS63 KIWX 201154 CCA AFDIWX Area Forecast Discussion...CORRECTION National Weather Service Northern Indiana 631 AM EDT Tue May 20 2025 .KEY MESSAGES... - Passing showers and thunderstorms today. Rain may be heavy at times. - Wind gusts from the east today at 35 to 40 mph. - Scattered showers and thunderstorms linger in the forecast through at least Thursday morning. && .DISCUSSION... Issued at 415 AM EDT Tue May 20 2025 A 998mb surface low is approaching from the Kansas City area. Wind gusts locally have been strengthening already this morning, with wind gusts of 30-32 knots at KLAF, KVPZ, and KSBN. This is despite soundings this hour that are rather stable. High resolution guidance suggests this synoptic wind field will strengthen through the morning and midday hours as the low approaches. Wind gusts of 40 mph are expected, especially along and west of US31. Wind will be maximized either from showers along the incoming warm front or, should skies scatter out briefly this afternoon in the wake of the warm front, a strong low-level jet could be able to mix down as well. Confidence is medium at best for how this plays out as forecast soundings are overall rather stable, yet model agreement is high and the existing wind field early this morning supports it. A line of thunderstorms moving into western Indiana this hour is exhibiting a weakening trend on infrared satellite along with a small decline in lightning. Our local environment, with an east wind and dew points in the low-to-mid 40s will be hostile for these incoming storms such that a weakening trend will continue. Showers will move through from southwest to northeast through the morning and midday hours. As the warm sector becomes established overhead this afternoon, scattered showers and storms develop south of US 24 amid 500 j/kg of MUCAPE and about 40 knots of shear. Forecast soundings are generally unimpressive locally, but small hail is a possibility from the tallest storms and, given the strong low- level wind field, perhaps a gusty storm collapse. Anomalously high PWATS and boundary- parallel flow permit the risk of heavy downpours. Scattered showers and thunderstorms taper off for a time overnight as a dry slot attempts to move overhead. This is followed by more shower chances Wednesday and even Thursday as the low continues its slow trek east. Drying out by Friday and most likely into the weekend. I`ve maintained some low POPs for coordination purposes, but guidance has shifted this weekend`s low pressure center farther south such that the best rain chances overall could be well south of US 24. An upper-level low swirling over the eastern Great Lakes Sunday night through Tuesday brings additional chances for rain while keeping temperatures cooler than normal. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 631 AM EDT Tue May 20 2025 An upper low pressure system located within a trough across the Plains States pivots towards the area today. A surface low pressure system develops and deepens over the area and this allows for some rain this morning through the day before a dry slot moves in this evening. With the rain, expect MVFR CIGs not too long after onset, but continued positive theta-e advection should allow times of IFR as well. Winds are expected to be out of the east for the bulk of the period and it is also expected to be breezy as a low level jet swings through the area. Gusts between 20 and 30 kts are expected to be prevailing through the period. SBN has a small chance to see LLWS with these winds, but think the case is marginal enough to leave it out. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...Small Craft Advisory until 9 AM EDT this morning for LMZ043- 046. Gale Warning until 5 PM EDT this afternoon for LMZ043-046. && $$ DISCUSSION...Brown AVIATION...Roller