Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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441 FXUS63 KIWX 161534 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 1134 AM EDT Sun Jun 16 2024 .KEY MESSAGES... -An excessive heat watch is in effect for portions of Northern Indiana and Northwest Ohio from Monday morning into Friday evening. Heat indices around 100 degrees are expected through the week. High temperatures will be in the upper 80s and 90s. -There are low chances for intermittent showers and thunderstorms this week, mainly in the afternoon and evening hours. Severe weather is not expected. -Today will be dry with highs in the upper 80s and low 90s. There are low chances for showers and thunderstorms tonight in Michigan counties. && .UPDATE... Issued at 1127 AM EDT Sun Jun 16 2024 Temperatures warming nicely across the area with mid 70s to low 80s across the board and further climbing expected to reach highs near or just above 90. Dewpoints will slowly increase through the afternoon with the highest values in the west and north (low to maybe mid 60s). Some changes were needed in the forecast, mainly wrt pops this evening/overnight as a well defined MCV, centered southwest of Ottumwa IA, will track ENE over the next 12 to 18 hours, reaching western IL during peak heating. With the influx of even higher dewpoints over there and the obvious trigger that can tap upwards of 2000-2500 J/KG of MLCAPE convection should fire in far NW IL by 20 or 21Z and then expand eastward and organize. HRRR seems to key in on this feature nicely and track it over southern Lake MI with the convection possibly surviving into at least our far NW counties before moving away. The most likely time frame is 3Z to 7Z but the SE extent of the area should be limited. Have introduced some chc pops further NW and made some tweaks to the slgt chc areas. If confidence increases on impacts, pops will need to be increased further possibly as early as the afternoon package. && .DISCUSSION... Issued at 444 AM EDT Sun Jun 16 2024 Todays main focus is the prolonged period of heat, which will last at least through Friday, with hints of highs in the 90s for Saturday/Sunday as well. Heat indices during peak heating each day are expected to linger around 100 degrees for the most part, with locations in NW Ohio/NE IN likely to see the most oppressive heat/humidity. Upon collaboration with the neighbors, opted to issue an excessive heat watch for a majority of the forecast area where I am feeling about 50% confident we may reach warning criteria in terms of Heat index (HI) values (105 or greater)-especially in NW Ohio. However, the main reason for the watch is the extended period of HIs around 100 degrees (warning criteria includes an exception for HIs around 100 degrees if they occur for 4 or more consecutive days). I am around 80% confident that we`ll see values of at least 95-100 degrees through Friday, possibly even lasting beyond the headline into early next week (depending on the model). Why not the whole CWA? I have lower confidence further west (especially southwest) because these areas look to be impacted most by convection. The upper level ridge shifts slowly southeast through the week, making us more and more susceptible to shortwaves rounding the ridge. Further west I have more frequent chances for rain/storms and thus greater cloud cover, which could limit things later on in the week. I suspect that they may need to issue a heat advisory for Monday in some areas outside of the current watch, but by Tuesday values fall closer to the low 90s. Because most of the convection is tied to daytime heating with no real flow beyond the occasional shortwave, expect more isolated to scattered coverage mainly tied to the afternoon/evening hours. This also makes pinning any specific timing/location down for precipitation difficult, which really shows in the wide variety of model solutions this week. Tried my best to limit pops to the best forcing and diurnal times, but still a ton of uncertainty. That being said, still issued for Michigan counties and further into IN because values linger between 95-100 fairly consistently through the week. It`s totally possible we end up running with an advisory vs a warning-depending on how the precipitation chances look to evolve. Have a mention in the HWO for counties outside of the watch area for now. In terms of models, it seems like the ECMWF/UKMET/Canadian have been consistently warm through the past few runs (including 00z ECMWF), whereas the GFS continues to be more consistently cooler (significantly). For example, on Wednesday the ECMWF has highs in NW OH around 94-96 degrees, but the GFS has highs in the upper 80s and low 90s. Opted to stick with the higher end of guidance given the pattern and consistency, but this is part of why we are just doing a watch vs a warning at this point. The other thing is that with the increased moisture advection into the area through mid week, heat indices may still be in the mid-upper 90s. The bottom line is this: It`s going to be hot. The time is now to prepare: be sure your a/c is working or know local cooling shelters, make a list of friends and family to check on and help them prepare, and possibly reschedule outdoor work or events. Make sure if you must work outside that you take breaks frequently and drink a lot of water. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 725 AM EDT Sun Jun 16 2024 VFR Conditions are expected at the TAF sites, with mainly high level cirrus and some mid level clouds to contend with. The only exception would be some of the high resolution models are starting to suggest that we could get passing showers/storms between 5 and 9z. Confidence is not terribly high with this, but if it does occur we could see a brief drop to MVFR/IFR. Added a prob30 group to KSBN to account for the potential. Otherwise, KFWA remains dry. Light east-southeast flow will become more south-southwest through the period, with gusts to around 22 kts at KSBN this afternoon. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Excessive Heat Watch from Monday morning through Friday evening for INZ005>009-014-017-018-024>027-032>034-104- 116-204-216. Air Quality Alert until midnight EDT tonight for INZ020. OH...Excessive Heat Watch from Monday morning through Friday evening for OHZ001-002-004-005-015-016-024-025. MI...Excessive Heat Watch from Monday morning through Friday evening for MIZ078>081-177-277. MARINE...None. && $$ UPDATE...Fisher DISCUSSION...MCD AVIATION...MCD