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FXUS63 KIWX 200642 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 242 AM EDT Fri Sep 20 2024 .KEY MESSAGES... - Showers and thunderstorms are expected this afternoon primarily west of Indiana State Route 15 (20-40% chance). - Remaining hot today and Saturday with highs approaching 90 degrees. - There are frequent chances for rain beginning Sunday. && .DISCUSSION... Issued at 239 AM EDT Fri Sep 20 2024 Showers and thunderstorms are expected this afternoon primarily west of Indiana State Route 15. Widespread severe storms are not expected, but damaging wind gusts from a storm or two cannot be ruled out. Showers and thunderstorms across Wisconsin and eastern Iowa early this morning are forming ahead of a 40-knot 500mb jet and in the vicinity of a cold front, whose parent low resides over central Manitoba. This activity is showing a gradual weakening trend on satellite, but embedded stronger cells continue to come and go over far northern Illinois. I'll be keeping a close eye on these this morning while maintaining the thinking that this round will decay prior to reaching Michiana. Overall, high resolution guidance is in strong agreement and initializes well across a variety of parameters this morning, thus increasing forecast confidence in rain occurring. This includes ensemble forecast soundings which verify reasonably well against observed soundings from 00z. While the Manitoba low is forecast to track northeast this morning, the trough aloft and aformentioned jet is already modifying our local air mass as dry air on upper- and mid- level water vapor is becoming pinched (retreating) in response to this jet approaching our eastern Great Lakes ridge. The 500-mb jet lingers over the Midwest today, providing at least some upper-level support. Dew points initialize well over the region and a corridor of low-60 degree dew points are expected to spread east ahead of the cold front. With highs once again well into the 80s, instability will be ample with no cap noted beyond the early-morning hours (in part why Wisconsin activity fails to reach Michiana this morning). Steep-low level lapse rates, a byproduct of low-level moisture that is gradually improving , indeed pose a marginal risk of damaging wind gusts from the tallest thunderstorms. Again, not expecting widespread severe storms today, but I have high confidence in scattered thunderstorms this afternoon primarily west of IN-15. Lastly, it should be noted that upstream soundings (e.g., GRB) saturated very well over the past 12 to 24 hours ahead of approaching rain, thus there is hope that the dry air mass that has plagued our area can be overcome. Beyond today, I am happy to report there are several chances for rain in the forecast as high pressure finally gets shunted over the far Northeast. Sunday through Tuesday, our upper-air pattern is characterized by a decaying ridge across the far Southern Plains extending into the Gulf. Meanwhile, a trough is ejecting from the Rockies, splitting the gap between the aformentioned ridge and a deep low swirling over Manitoba and Ontario. As a result, we're mercifully in line for periodic showers and thunderstorms Sunday through Tuesday paired with temperatures closer to normal. How this upper-air pattern evolves late in the week is unclear, with some guidance suggesting a cut-off low to finish the week. WPC forecast rainfall today through Friday morning (next week) favors rainfall in excess of 1" for the forecast area. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 121 AM EDT Fri Sep 20 2024 Dew points are expected to level off overnight in the mid 50s as temperatures slowly fall into the upper 50s and low to mid 60s. This miss for cross-over temperatures likely yields only patchy ground fog in the FWA area. This, as a moisture axis makes its way into the area for Friday. Winds become more southwesterly during the day Friday and increase chances for showers during the midday and afternoon hours. At this point, it's hard to have confidence in chances for rain given antecedent dry conditions, but the chance is at least there. Will have a VCTS at SBN in the evening and a -SHRA for FWA into early overnight. With all of this in mind, will lean towards prevailing VFR through the period at both sites. Some thought towards potential lowered VIS within heavier showers may need to be considered. && .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...Brown AVIATION...Roller

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