Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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929 FXUS63 KIWX 131920 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 320 PM EDT Thu Jun 13 2024 .KEY MESSAGES... - Scattered strong to severe storms are possible from 4 PM to midnight EDT tonight, with the main threat being damaging wind gusts. Additional hazards include hail 1-2" in diameter and a brief, isolated tornado or two. - A long duration heat wave begins on Sunday, June 16th. Highs will be in the low to mid 90s with heat indices upwards of 100 to 105 degrees starting on Father`s Day through at least the middle of next week! Can`t rule out a few low chances (20% or less) for showers and storms but this timeframe looks mainly dry. && .DISCUSSION... Issued at 309 PM EDT Thu Jun 13 2024 Stay weather aware late this afternoon and evening as strong to severe thunderstorms are possible. SPC has maintained a Slight Risk (level 2 of 5) for much of our area. GOES satellite imagery this afternoon shows ongoing clearing for much of the lower Great Lakes. There is also a growing field of developing cumulus near Chicago out ahead of the cold front that is currently over SE Wisconsin and NW Illinois. High temperatures will approach the low 90s with dewpoints in the low to mid 60s. Moderate MLCAPE of around 1000 J/kg combined with ~40 kts of shear orthogonal to the aforementioned frontal boundary will result in a favorable environment for severe weather tonight. As the cold front and attendant shortwave trough sweep eastward, storms should initiate between 4 to 6 PM EDT over Lake Michigan and far southwest Lower Michigan. These initial discrete cells could merge into clusters/a QLCS as they grow upscale, although the latest hi-res model guidance still differs in the coverage and intensity of this convection. Expect storms to move south/southeastward throughout the evening hours. Our southeast CWA may see additional storm development after 8 PM EDT as an MCS develops in northern/central Illinois. As storms initially develop late this afternoon, they may pose an initial threat for hail, but as storms grow upscale, the primary concern will become damaging winds. Inverted-v HRRR, RAP, and NAM soundings have 800-1100 J/kg of DCAPE, indicating a favorable environment for damaging downburst winds. Throughout the event, damaging winds 60-70 mph will be the main threat across much of the area, but hail 1-2" in diameter, torrential rain, and a brief, isolated tornado or two are all possible as well. In addition, PWAT values are around 1.5 to 1.75", which is near the 90th percentile for this time of the year. This could bode very efficient rainfall rates and some localized flooding potential as well this evening (especially in the SW CWA where additional storm development is possible). Most storms should dissipate before midnight EDT, but a few may linger in the SW CWA as late as 3 AM EDT Friday. Friday and Saturday look to be slightly `cooler` (highs upper 70s to mid 80s) and dry in the wake of the cold front. However, starting Sunday, the first prolonged stretch of hot and humid summer days will begin! An early season heatwave is likely, with high confidence in near record temperatures and increasing humidity. Surface high pressure and impressive upper level ridging will build across much of the eastern CONUS this weekend, setting the stage for a `heat dome` to set up. Highs will be in the low to mid 90s with heat indices pushing 100 to 105 degrees starting on Father`s Day through at least the middle of next week! Near record overnight lows in the low to mid 70s will offer little to no relief from the heat. This is the typical summertime "Ring of Fire" pattern for the Upper Midwest and Great Lakes regions where any clusters of storms can develop and tend to ride around the periphery of the heat dome. For the next 3 to 7 days, subsidence should keep precipitation chances at bay, with only a few low chances (20% or less) for rain/storms). There is growing confidence that Heat Advisories or even an Excessive Heat Warning may be need for next week. Prepare now for the incoming heat wave next week! Those without AC, elderly or young children, or who are susceptible to heat may be especially vulnerable. Find out where cooler shelters are in your town, stay hydrated, and prepare to limit activities outdoor during peak heating hours. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 128 PM EDT Thu Jun 13 2024 An active TAF period is anticipated amid the risk for severe thunderstorms, especially at KSBN. Cumulus clouds are developing over Illinois and southern Michigan ahead of a cold front located near the WI-IA-IL lines. Severe thunderstorms are expected to develop near the Michigan state line and drop south. Strong wind gusts, hail, and heavy rain are the primary concerns. Synoptic wind gusts abate behind these thunderstorms, through wind gradually veers through the night behind the cold front. There is a non-zero chance of MVFR ceilings tonight amid post- frontal stratus. Probabilities are generally near 30% or so, per the in-house blend. Therefore, retained the mention at KSBN but avoided the introduction of such ceilings at KFWA for the time being. Satellite trends will be monitored. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Johnson AVIATION...Brown