Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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205 FXUS63 KIWX 240523 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 123 AM EDT Tue Sep 24 2024 .KEY MESSAGES... - Rain showers will expand in coverage overnight with greatest coverage expected across northeast Indiana and northwest Ohio late night. - Scattered showers and storms expected later Tuesday afternoon/early Tuesday evening. An isolated strong to severe thunderstorm is possible. - Dry midweek before a low chance (20-30%) of showers late this week into the weekend. && .UPDATE... Issued at 900 PM EDT Mon Sep 23 2024 Low level winds have backed this evening in response to emergence of next upstream mid/upper level trough across the Central Plains. This has allowed for some strengthening of advective forcing as low level theta-e gradient from central IL to central IN has started a retreat back northward. Showers south of the US-24 corridor this evening should remain on the light side with little support for more organized synoptic lift behind this advective forcing. A more focused area of stronger showers/embedded storms has developed across eastern MO/southwest IL this evening. This appears to be at the nose of a 90 knot upper jet streak sampled by KOUN 00Z RAOB data. The left exit region of this upper jet streak will continue to migrate across the Ohio River Valley into early Tuesday morning. Another area of forcing to monitor for the overnight may be tied more to a maturing 900-800 mb circulation across central IL as the Central Plains upper level wave lifts northeast. This low level frontogenetic flow may support enhancement to showers from central IL into NW IN/SW MI late tonight/early Tuesday. Best rainfall rates overnight into early Tuesday are still expected in association with more pronounced upper jet forcing, which should also be co-located with some strengthening low level moisture convergence from central IN into northwest OH via a modest southerly low level jet. Additional refinement to PoPs will certainly be needed as these sharper forcing areas evolve overnight, but previous forecasted trends to likely/categorical PoPs still seem in order. && .DISCUSSION... Issued at 125 PM EDT Mon Sep 23 2024 Abundant cloud cover today has effectively kept temperatures down. Most locations will only see highs in the 60s, although a few may get up to around 70 degrees. A low pressure system currently centered over Arkansas and Missouri will make its way northeastward this evening. Showers could begin moving into southwest portions of the forecast area as early as 6-7 pm EDT. While isolated thunder is possible, chances are slim due to a lack of instability. Showers will continue through the night, mainly south of US 24. Then as the low tracks farther northeast by daybreak, shower activity will also shift northward. The surface low will cross the region from southwest to northeast (White County, IN to Williams and Fulton counties in Ohio) on Tuesday afternoon. In its vicinity and in the warm sector to the southeast will be the best chances for thunderstorms. It is in this area where bulk shear will be 30-40 kts and CAPE in excess of 1500 J/kg that SPC has extended the Marginal Risk for severe storms from around 3 pm through 9 pm. Damaging wind or hail could be possible, or even an isolated tornado. Wednesday will be mostly dry, but a few lingering showers may still be possible as the upper trough crosses the Great Lakes. On Thursday and Friday, the region will again be stuck between low pressure systems and high pressure will build back in. It will be dry and temperatures will warm, although it will not be as hot as last week, with highs confined mainly to the upper 70s or low 80s. Model uncertainty comes into play for the weekend concerning the position of an upper low to the southwest and a tropical system near the west coast of Florida. Consensus is that we should see more rain by Sunday into Monday. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 123 AM EDT Tue Sep 24 2024 Surface low pressure will move into the area today with multiple round of showers expected. Ceilings will steadily lower through the early morning as this system approaches. IFR ceilings already at KSBN with some brief LIFR possible around 12Z. KFWA will take a bit more time to drop given more dry air entrainment but IFR is likely here as well by around 12Z. Some improvement expected with diurnal mixing especially at KFWA where low track may favor much better mix out. IFR returns behind the low Tuesday night though. There is some chance of thunder (especially at KFWA) but confidence in timing and coverage remains very low at this point. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ UPDATE...Marsili DISCUSSION...Cobb AVIATION...AGD