Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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147 FXUS63 KIWX 241000 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 600 AM EDT Mon Jun 24 2024 .KEY MESSAGES... - Seasonable temperatures and low humidity values today with dry weather persisting. - Chance of storms increase overnight tonight with some potential of thunderstorm wind gusts over 40 mph. - Scattered thunderstorms are possible Tuesday with some potential of strong to severe thunderstorms Tuesday and Tuesday night. Confidence remains low in timing and the extent of the severe weather threat. - If lesser storm coverage/cloud cover is realized for Tuesday, heat indices may approach the upper 90s to around 100 Tuesday afternoon across portions of the area. && .DISCUSSION... Issued at 335 AM EDT Mon Jun 24 2024 Main theme of previous forecast remains intact. A quiet Monday will be followed by building heat and humidity for Tuesday, but the extent of this heat and humidity will depend on thunderstorm and cloud evolution late tonight into Tuesday. There is a potential of strong to severe storms late tonight into Tuesday night, but the extent of this threat and timing greatest chances remains low confidence. In the near term, a small scale but compact upper level short wave continues to drop across southeast Lower Michigan. A small pocket of 500 J/kg MUCAPE did allow maintenance of isolated thunderstorms across central Lower MI, but this line has weakened as it has approached south central Lower Michigan. A few showers and sprinkles can be expected over next few hours across southern Lower Michigan. Otherwise today should be a quiet, pleasant day with seasonable high temperatures and weak winds under the influence of low level anticyclone. Low level thermal trough will be positioned across the area with a dry air mass in place and afternoon dew points likely mixing out into the mid 50s in many spots. For tonight, highly progressive pattern allows for quick rebound in mid level heights across the western Great Lakes with a strong low level jet developing from the Central Plains into Minnesota. Strong low level mass/moisture convergence at the nose of this jet should force one or two convective systems tonight across the Upper Midwest. Evolution of mid and upper level pattern will allow a very strong low-mid level theta-e gradient to push into the region overnight. Some concern for MCS activity tonight given this strong instability gradient across the region and eastward shifting strong mid level lapse rates. In addition, the development of the strong low level jet across the MS Valley will result in north to south Corfidi vectors tonight and a southward preference to MCS propagation from the Upper Midwest. Given this low level jet interaction with outflows and stronger instability back across the Corn Belt, would suspect the upwind propagation idea among many of the HREF members would be preferred as opposed to forward propagation. This would put local area in possible path of a potential upstream MCS late tonight into Tuesday morning. As is the case in these type of setups, difficult to have much confidence in exactly where potential convective system initiates tonight and where it will track. Late arrival (low level CIN) and weaker deep layer shear with southward extent across the southern Great Lakes and Ohio Valley, may allow for lesser severe threat locally with a Marginal Day 1 Risk for western two thirds of the area late tonight. One caveat is these convective disturbances have localized stronger shear environments and if well developed cold pool can develop, cannot discount some potential of severe thunderstorm wind gusts overnight into early Tuesday. Forecast confidence further dwindles for Tuesday with a high amount of dependence on how potential AM storms/outflow boundaries set up during the day. The potential does exist for an outflow boundary to lay out across the area from these storms which could be possible focal point for more storm development in the afternoon. The environment Tuesday afternoon could be characterized by moderate to strong instability, but guidance consensus suggests shear magnitudes decrease through the afternoon without a well defined synoptic scale disturbance to latch onto. If stronger overnight convection develops tonight, outflow boundary could be pushed farther south with lower thunderstorm potential Tuesday afternoon/early evening. The uncertainty in convective forecast results in low confidence in extent of heat indices Tuesday afternoon. Overall trend may be to slightly lower confidence in advisory level heat indices with a suspicion that outflow boundary/remnant cloud cover could be limiting factor. Opted for middle of road solution given all the uncertainties with peak afternoon heat indices from lower 90s north to mid-upper 90s south on Tuesday. For Tuesday night, thunderstorms chances will likely become renewed as low amplitude upstream short wave approaches from the west interacting with what should be rich west-east oriented low level theta-e ridge. These storm chances may continue through the night into early Wednesday across the south as low level convergence axis shifts southward. Still feel that better focus for stronger storms Wednesday afternoon may end up just south of the area with outflows pushing effective boundary south of the area. Cooler and less humid conditions build in for Thursday, but the highly progressive nature of this pattern will allow for highs back into the mid 80s to around 90 by Saturday. Another potential frontal passage Saturday would bring more chances of showers and storms for first part of weekend, but timing of this fropa will need to be resolved over next several forecast cycles. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 556 AM EDT Mon Jun 24 2024 Tranquil weather within the critical TAF period thanks to high pressure in place. This high pressure gives way to shortwave aloft and the risk of showers and storms approaching KSBN in the latter portion of the TAF period. Confidence is medium at best. The anticipated line of storms is forecast to develop over the MN/WI line very late this afternoon and dive ESE. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Marsili AVIATION...Brown