Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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347 FXUS63 KIWX 202322 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 722 PM EDT Fri Sep 20 2024 .KEY MESSAGES... - Some areas may see rainfall this afternoon with widely scattered to scattered showers/storms. - One more warm day Saturday with highs possibly reaching (or exceeding) 90 degrees before a trend to cooler temperatures. - Confidence increasing on 1 or more chances for much needed rainfall Sunday into Monday, with timing/coverage details still to be sorted out. && .DISCUSSION... Issued at 312 PM EDT Fri Sep 20 2024 An area of storms developed over southern Lake Michigan and has worked inland, holding its own, but struggling to develop further SW despite unstable conditions. Main wind shift remains back over Chicago, working slowly east. Big question is does the convection expand further southwest of have we seen the southern extent of the needed rainfall. So far the main features have been brief but heavy rainfall with locations picking up a quick half inch to over an inch in the stronger storms. Have adjusted pops to lower somewhat further SW based on satellite trends. Agitated cu field still is showing up so suspect more widely scattered development could take place with a newly developed cell near Rensselaer. Everything will move east at around 25 mph and is expected to weaken after 00Z with loss of heating. Higher dewpoints will remain in place overnight with drier air not arriving till Saturday. After coordination, have added patchy fog with areas that manage to see some rainfall today seeing some potential for locally dense fog. One more hot day is in store by mid Sept standards for Sat with highs at least into the mid to maybe upper 80s. MAV guidance remains rather aggressive on highs in the low to middle 90s, possibly due to increasing mixing/subsidence. Not ready to jump into that arena, but something to watch in later forecasts. Confidence does continue to increase on 1 or more chances for showers and storms, possibly as early as Sunday afternoon, lingering into Monday night as a series of disturbances move into the area and northern stream trough digs and deepens. Trends seem to suggest the first round being Sun afternoon/evening with another Monday afternoon and evening. Keeping pops capped at likely for now, but signs point towards at least some needed rainfall for many areas. Models diverge on handling of the trough through the rest of the period (and beyond) ranging from strong ridging overhead to a deep cutoff low near/west of the area. To further complicate things, some sort of tropical development is expected next week, but location and track of this feature is equally uncertain. At least a brief dry period seems likely late Tue night into Wednesday before remainder of forecast has slgt chc to chc pops. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 715 PM EDT Fri Sep 20 2024 Behind the cold front, conditions will be very favorable for the development of fog overnight. Winds become light and variable this evening, and with leftover ground moisture from today`s rain, this will result in areas of patchy dense fog Saturday from about 10Z to 13Z. For both KFWA and KSBN, the NBM has about a 60% chance for LIFR ceilings, a 40% chance for IFR ceilings, and a 30% chance for visibilities less than 1 mile. With such strong probabilities, fog appears likely to develop Saturday morning, and as such, have added a TEMPO group into the TAFs to reflect this. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for INZ005-012>015-022-023-104-116-204-216. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Fisher AVIATION...Johnson