Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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649 FXUS63 KIWX 181150 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 750 AM EDT Tue Jun 18 2024 .KEY MESSAGES... - There are nearly daily low chances for showers and thunderstorms this week, especially in the afternoon and evening hours. Expect coverage to be widely scattered. - The storm prediction center has portions of Northwest Ohio in a marginal risk for severe storms today, particularly this afternoon. Gusty winds and heavy rain are the primary threats in any stronger storms. Hail is also possible. Isolated stronger storms are possible outside of the risk area as well. - Excessive Heat warnings and advisories are in effect due to an extended period of hot and humid conditions. Max heat indices this week will range from around 95 to 105, with the highest values in the warning area and in urban locations. Overnight lows in the 70s will provide little relief from the heat. High temperatures will be in the upper 80s and 90s. && .DISCUSSION... Issued at 454 AM EDT Tue Jun 18 2024 Bottom line up front: Dangerous heat and humidity is expected. Excessive Heat warnings and advisories are in effect. Heat indices through at least Friday look to be in the 95 to 100 degree range for most, with values as high as 105 looking likely in the warning area. Both headlines continue through Friday at 8 pm EDT. Will likely need to extend the advisory/warning into Saturday given the current forecasted heat indices will be around 100 once again, but there are more significant chances for precipitation so held off for now. Today will be the coolest of the week thanks to more expansive cloud cover and the showers and thunderstorms expected through the early evening, however models are indicating a westward shift of the ridge axis from yesterday---meaning we`ll see better potential Wed/Thu/Fri for those higher heat indices (and potentially Saturday). As a reminder in the event there are any questions regarding headlines, our local criteria is: -Heat Advisory: "A heat index (HI) around 100 degrees or higher. Consider a warning if the maximum HI is going to be between 95 to 100 degrees for more than 4 consecutive days." -Warning criteria: HI >105 and a minimum HI >75F for a 48 hour period (or if the advisory criteria continues for more than 4 consecutive days). This is because heat impacts are cumulative- particularly for more vulnerable urban populations. Otherwise, the main change to the forecast today was to narrow down chances for showers and thunderstorms, which appears futile given the plethora of conflicting model guidance. Kept it broad and general for now. However, suspect the morning shower and thunderstorm activity we`re seeing at the nose of a LLJ/increased moisture transport into our area (that none of the models had that far east ha!) will increase in coverage through the afternoon as we gain instability from daytime heating. Similar to the past few days, we`ve had a few isolated severe storms and today is no exception. The storm prediction center has portions of NW OH in a marginal risk for severe storms, focused in the afternoon, thanks to a potent shortwave currently over IL rounding the ridge-which will lift north and then start heading eastward through the late afternoon/early evening. I think this is reasonable, with damaging winds being the main threat with the strongest storms. Outside of that we could see an isolated strong to severe storm, but the best chance will be in NW OH. DCAPE values look to end up around 1000 J/Kg in that area, so we may see more of the downburst/microburst situations. Hail is possible but less likely given the higher freezing level (14Kft) and -20C (26kft). It`s more likely to be heavy rain given the humid air mass. Two cells in the huntington area this morning produced about 0.25" in 10 minutes and gusted to around 30-40 mph. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 745 AM EDT Tue Jun 18 2024 Predominantly VFR conditions at the TAF sites, outside of within any heavier showers or thunderstorms. For now, kept things pretty broad brushed as there is a lot of uncertainty with regards to convection. Morning rain is moving into KSBN area for the morning from the south, then as a shortwave moves through this afternoon expect potential thunderstorm development. Its possible we see a few thunderstorms develop within the showers around 15z. Some of the guidance has the showers diminishing on the south end and missing KFWA late this morning early AM, but others suggest it will make it and storms will impact the airport. Kept light rain 16-21z with VCTS potential. Otherwise, south-southwest winds will gust up to around 20-25 knots. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Friday for INZ005>008- 012>015-020-022-023-103-104-116-203-204-216. Excessive Heat Warning until 8 PM EDT Friday for INZ009-017- 018-024>027-032>034. OH...Excessive Heat Warning until 8 PM EDT Friday for OHZ001-002- 004-005-015-016-024-025. MI...Heat Advisory until 8 PM EDT Friday for MIZ078>081-177-277. MARINE...None. && $$ DISCUSSION... AVIATION...MCD