Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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914 FXUS63 KIWX 170603 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 203 AM EDT Mon Jun 17 2024 .KEY MESSAGES... - Far northern Indiana and southern Michigan may see showers and thunderstorms between 8 pm and 4 am. Gusty winds and heavy rain will be the main concerns. - An Excessive Heat Watch remains in effect due to an extended period of hot and humid conditions. - Widely scattered afternoon and evening thunderstorms are possible Monday and Tuesday. && .UPDATE... Issued at 740 PM EDT Sun Jun 16 2024 Potent MCV will lift into southern MI this evening and support SCT convection given nearly 2000 J/kg MUCAPE. Boundary layer stabilization will likely prevent any severe wind gusts/strong convection but latest HRRR has suggested some storms continuing through much of the overnight in our far northern counties. Will update PoP`s accordingly. A few showers/storms are firing along the gust front but HRRR and RAP suggest additional development behind this front as the MCV passes. && .DISCUSSION... Issued at 226 PM EDT Sun Jun 16 2024 The main story of the upcoming forecast period remains with hot and humid conditions already starting today and expected to further intensify, especially in the second half of the week with afternoon/evening heat indices in the 95 to 100 degree range and limited cooling during the overnight hours. Extensive coordination with surrounding offices as resulted in a continuation of the Excessive Heat Watch with the reasoning to be explained below. Regardless of what headlines may or may not exist, the extended period of heat and humidity will still pose an issue to those working or playing outdoors, those without adequate means to cool off (both day and night) and those with health problems made worse by the hot and humid conditions. Afternoon temperatures have climbed into the upper 80s with some potential for far SW areas to still touch 90. A large gradient in dewpoints was also in place across the area with upper 40s far NE to mid 60s SW. Overnight lows for tonight and much of the upcoming week will end up in the lower to middle 70s, making for rather unpleasant sleeping. While many areas will remain dry into at least Monday morning, far NW locations may see a chance for showers and thunderstorms later this evening into the overnight hours as a well defined mcv heading towards the Quad Cities, continues to move ENE and force additional showers and storms across northern IL. SPC upgraded to a slight risk ahead of this feature with the marginal risk being expanded slightly to roughly a DeMotte to South Bend to Kalamazoo line. Models are varying somewhat on the strength of storms as they pass over Lake Michigan and enter SW Lower MI/far NW Indiana and move ENE. Some models also expand the precipitation further south to at least US-6 and maybe even a bit more. For the moment have limited pops to slgt chc to chc and will defer any further increases to the evening shift. Gusty winds and heavy rain will be the main concerns. While the hot and muggy conditions are fairly straight forward, finer details in cloud cover, chances for showers/storms and mixing out of dewpoints with drying ground conditions lead to challenges in upgrading the watch to a Heat Advisory or Excessive Heat Warning. The greatest concerns for the heat still exist moreso Wednesday and beyond as the cumulative effects of the heat as well as lack of rain chances all lead to greater impacts. Weak disturbances and subtle forcing mechanisms could help spark widely scattered showers and thunderstorms during the afternoon and evening hours of Monday and Tuesday. One mechanism could be any boundaries that may be left over from the convection tonight. While it will be unstable and generally uncapped, hard to assign more than a slgt chc to maybe chc of convection at this point. Any storms that manage to form will not move much and with the moist conditions will produce very heavy rain and maybe locally gusty winds. Models do key in on a disturbance working north Monday night that may help increase chances for showers and storms, but think models may be overdone somewhat with general consensus of offices being to keep pops silent or slgt. Chances for showers and thunderstorms may increase over the weekend as the ridge axis orients more west to east and sinks some. Best chances may exist Sunday but if these don`t pan out, then the potentially dangerous heat will persist. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 156 AM EDT Mon Jun 17 2024 An earlier MCV moved north of the area; however, isolated storms were still firing on the outflow boundary were SPC CAPEs were at 1500 J/Kg and precipitable water values close to 1.75". Mentioned VCTS early at SBN, otherwise winds should stay from the south with VFR conditions. More isolated storms again later today with max heating; opted to keep SBN and FWA dry given the isolated nature and low confidence of the storms. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Excessive Heat Watch from 11 AM EDT this morning through Friday evening for INZ005>009-014-017-018-024>027-032>034- 104-116-204-216. OH...Excessive Heat Watch from 11 AM EDT this morning through Friday evening for OHZ001-002-004-005-015-016-024-025. MI...Excessive Heat Watch from 11 AM EDT this morning through Friday evening for MIZ078>081-177-277. Air Quality Alert until midnight EDT tonight for MIZ078-177- 277. MARINE...None. && $$ UPDATE...AGD DISCUSSION...Fisher AVIATION...Skipper