Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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743 FXUS63 KIWX 201821 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 221 PM EDT Mon May 20 2024 .KEY MESSAGES... - A strong to locally severe thunderstorm is possible between 6 and 10 pm in NW Indiana/SW Lower MI as well as locally heavy rain. - Strong to severe thunderstorms are possible late Tuesday night, mainly west of IN-15 and then again along and east of I-69 Wednesday afternoon and evening. - Warm and muggy conditions to be replaced by somewhat cooler and less humid air late this week into the Memorial Day weekend with some chances for showers and storms. && .DISCUSSION... Issued at 214 PM EDT Mon May 20 2024 Very summer-like pattern comes with summer like challenges for convection over the next couple of days in a rather moist and diurnally unstable environment. Highs the next several days will soar well into the 80s Initial focus, with greatest (albeit still somewhat reserved) confidence being with impacts of a MCV set to move across SE Wisconsin later this afternoon. While the best dynamics remain northwest of the area, a spoke of the wave does clip far NW areas, resulting in some weak convergence that may be sufficient to develop scattered showers and storms in the 22-00Z time frame. NAM suite overly unimpressed with the development with other CAMs a bit more confident on some development (HRRR the greatest). Much like yesterday, shear profiles are rather paltry (20 kts or less) resulting in more pulse type convection that could drop a good deal of rain in a short time along with some threat for locally gusty winds/small hail. Confidence in eastward extent in the 00Z-04Z period decreases with loss of diurnal heating and continued NE track of the MCV removing the already limited convergence. Concerned that likely pops this evening may be overdone, but if it is going to occur, location is about right. Have made some adjustments to pops to reflect a bit more inland extent to the storms but continue with a weakening trend into the overnight hours. Between 9Z Tue and quite possibly through 4-6Z Wed the best forcing will likely remain well north into MI with the warm front and well west with the cold front, resulting in a dry forecast despite increasing instability and shear during the afternoon and evening hours. 700 mb temps of +11 to +12 C edge in as well, further capping off any development. While a stray shower or storm could form across northern parts of the area during the morning and maybe late afternoon in the far W, by far the best chances look to wait to closer to 6Z Wed and beyond as a line of strong to severe storms will likely have moved across IL and be edging into western areas. A few CAMs show some possible additional development ahead of the line on more of a pre-frontal trough late evening with the main line then catching up. Several models show a fair amount of SFC based CIN taking shape overnight and the 50 kts of 0-6 km shear actually decreases just ahead of the approaching convection (still maintained along and behind). If the line holds together into the overnight hours, pockets of damaging winds and some large hail would be the main concerns. Slight risk in NW areas appears reasonable still for Tuesday night with greatest chances remaining well west of the area across E IA/W IL where a moderate risk for severe storms now exists. Cold front will ease its way through Wednesday with the potential for some lingering cloud cover early. CAMs vary greatly on potential for development along and ahead of the front with stronger signals maybe residing just SE of our area during the afternoon/eve hours as better upper level dynamics take time to catch up with the front. DY3 slight risk is warranted at this point, but may change over the next 24 to 36 hours as the mesoscale impacts of Tuesday night`s convection becomes more apparent. New blend of models expands the likely pops well NW to match where the better chance for storms may exist (SE third or so-roughly I-69 east) and lingers into Wednesday evening. This could very well be overdone, but given the proximity of the front can`t entirely dismiss. Frontal boundary will settle south of the area, with models continuing to indicate a weak disturbance edging north from TX Thursday evening towards the Ohio Valley for Friday. Additional waves move in from the northern Plains the rest of the weekend into early next week resulting in several period of slgt chc to chc pops over the holiday weekend. Don`t think by any means it will be a washout, but something to monitor in the coming days. The cloud cover will help keep it somewhat cooler during the day (70s). && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 124 PM EDT Mon May 20 2024 Mid level ridging and capping with 700 mb temperatures above normal across the area is expected to keep pop shower and thunderstorm activity at bay until around 00z or so. As a vorticity maximum heads into the Western Great Lakes and Lower Michigan area, left over instability may be able to maintain some level of strong thunderstorm activity into SBN terminals, but less of a chance to reach FWA. Can`t rule out at least an MVFR VISBY restriction, but confidence is low on that. Additional flight restrictions will be possible Tuesday morning as Lake MI marine air filters in, but confidence on the extent of that is also low. Will address with a tempo group for now. Also, expect gusty winds this afternoon to die down this evening. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Fisher AVIATION...Roller