Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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819 FXUS63 KIND 231025 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 625 AM EDT Mon Sep 23 2024 .KEY MESSAGES... - Widespread showers and a few thunderstorms through Tuesday - Seasonable temperatures for much of the week with highs in the 70s and lower 80s and lows in the 50s and 60s - Rain chances return late week into the weekend. && .SHORT TERM (Today and tonight)... Issued at 300 AM EDT Mon Sep 23 2024 Radar loop is showing only a couple of stray showers over Randolph and Henry counties early this overnight. Surface analysis was showing the cold front has moved to near the Ohio River, and GOES-16 RGB nighttime channel and surface obs were indicating a stratus deck was expanding southeast to near the I-70 corridor. This area of clouds will be expanding southeast across the rest of central Indiana overnight. Hi-Res soundings are indicating a very moist column with an inversion that should hold most if not all of today. Only some drying in the near surface was noted in the soundings, suggesting the clouds will hang around all with only some lifting of the ceilings. This will keep temperatures way down. As such, afternoon temperatures will only reach slightly below normal readings in the lower to middle 70s. DESI grand ensemble 25th percentile 2m temperatures even suggest the upper Wabash Valley may not see 70 degrees. GOES-16 H20 vapor imagery was showing a positively tilted trough from Nebraska to southeastern Colorado and northern New Mexico. This trough will move east into the Missouri Valley by 12z Tuesday. This trough will help spin up surface waves along the Ohio Valley front. This will result in showers returning northeastward across central Indiana this morning into tonight with the best chances (80%) during the overnight. Only weak instability over southwestern parts suggest any thunder will mostly be embedded and south of I-74. PWATs to around 1.75 inches which is above the 75th percentile for this area along with synoptic lift suggest around a half inch of rain looks good tonight for most areas. Again, best chances will be overnight, when a modest 30 knot low level jet points in from the southwest. The thick clouds and moist boundary layer will mean overnight temperatures should remain mild in the 60s. && .LONG TERM (Tuesday through Sunday)... Issued at 300 AM EDT Mon Sep 23 2024 Guidance continues to consistently show another slug of rainfall with a weak low pressure system continuing beyond the short term into Tuesday, before exiting the area Tuesday night. Beyond then, forecast confidence is modest at best, with deterministic models in some cases quite different than even 24 hours ago, but appearing to converge around a solution that shows a large cutoff low off to our southwest mid to late week as a potential tropical cyclone is drawn northward into the Gulf and gradually absorbed into the cutoff low after undergoing a Fujiwhara effect type interaction early in the weekend. This will necessitate low to middling chances for showers Thursday onward, though this is likely a bit overdone with some dry periods likely in that time frame. That said, potential will exist late week into early next for a solid soaking rainfall of perhaps a welcome 1 to 2 inches, which would be another contributor toward halting further deterioration of the hydrologic situation, though perhaps only producing minor improvement. Temperatures throughout the long term will remain near to a bit below normal given the presence of the upper low and eventually tropical remnants, though extent in time and space of cloud cover and precipitation as the long term wears on will have a major impact on diurnal range. && .AVIATION (12Z TAF Issuance)... Issued at 624 AM EDT Mon Sep 23 2024 Impacts: - IFR and possibly worse ceilings through 15-18z and possibly again after 06z Tuesday in convection - Showers will be moving in as early as this afternoon with the most coverage after 23z Discussion: A front will stall near the Ohio River. A saturated boundary layer and light winds have resulted in IFR ceilings to all the terminals this overnight and early morning. Flying conditions will improve somewhat this afternoon as the boundary layer dries per Hi- Res soundings. Then, a surface wave will lift northeast along the front. This will bring in an area of showers from southwest to northeast this afternoon and tonight. Winds will be light northwest and then north. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...MK LONG TERM...Nield AVIATION...MK