Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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990 FXUS63 KIND 221344 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 944 AM EDT Sun Sep 22 2024 .KEY MESSAGES... - Widespread showers and thunderstorms today and this evening - Turning cooler and more active with additional rain chances early next week && .FORECAST UPDATE... Issued at 944 AM EDT Sun Sep 22 2024 Clouds have increased from the west through the morning as rain with embedded thunder slowly spreads into the Wabash Valley. Temperatures at 13Z were generally in the upper 60s and lower 70s. The ongoing forecast is in good shape for today with the focus for the morning update on making subtle adjustments based on current trends. The main adjustment in the near term is to slow down eastward expansion of the rain over the next few hours as lingering dry air over eastern Indiana has aided in slowing down arrival times to rain. That being said...with low pressure now over western Illinois and a steady infusion of deeper moisture from the southwest...expect rain showers to become numerous over the region through early afternoon. Instability will be limited over much of the forecast area with storms likely to be isolated. There is potential for a subtle uptick in convection over the lower Wabash Valley by late day where the airmass will be most unstable. Highs ranging from the mid 70s to the lower 80s continue to look reasonable with the increased cloud coverage and rain. Zone and grid updates out. && .SHORT TERM (Today and tonight)... Issued at 303 AM EDT Sun Sep 22 2024 Beneficial rainfall is on the way to central Indiana starting late this weekend as a frontal system takes aim on the Ohio Valley and Great Lakes. MRMS reflectivity loop was showing large areas of convection from Lake Michigan to the southern Plains near an approaching cold front. Closer to home, IR satellite and obs were showing only patches of AC over central Indiana. An associated warm front extending from a low center over southeastern Wisconsin to the upper Wabash Valley and northern Kentucky, was quiet early this morning aided by upper ridging. CAMs and Hi-Res models have showed a slowing trend regarding when the upstream convection enters the Wabash Valley with all but the Wabash Valley now expected to stay dry overnight. However, combination of synoptic forcing, weak instability and deep moisture per Hi-Res soundings and max moving average PWATs to 2 inches per SPC ILX sounding climatology, support widespread convection coverage over central Indiana this morning over the Wabash Valley and afternoon over areas near and east US-31. After the first wave moves through, there may be a brief break, but more convection will fire up late this afternoon and evening, closer to the front, as it moves through from northwest to southeast tonight. With such deep moisture, synoptic support and sufficient instability, the 90th percentile DESI grand ensemble 24 hour QPF ending 12z Monday data looks to have a better handle on things. Most locales should see a quarter inch by Monday morning with 1 inch amounts amounts possible in the most robust convection. The increase in cloud cover and convection will limit temperatures today. Many locales will not reach 80 degrees per DESI grand ensemble 25th to 75th percentile 2m temperatures. That said, overnight lows will only get down to the 60s due to increasing low clouds and overall saturated boundary layer. && .LONG TERM (Monday through Saturday)... Issued at 303 AM EDT Sun Sep 22 2024 Guidance continues to advertise a much milder week across central Indiana than in recent days, with highs in the 70s and lows in the 50s with the exception of Monday night, when southern areas may only bottom out in the low 60s. There is relatively high confidence in a solid rainfall early in the work week - with chances highest Monday night into Tuesday. Beyond mid week, forecast confidence is minimal as run-to-run and model-to- model inconsistencies and fluctuations continue with respect to the overall pattern. The primary struggle is in the potential for the larger scale upper trough to cut off from the main westerlies and linger across the central or eastern CONUS, which could then introduce the possibility of this large scale circulation also absorbing potential tropical remnants as well. Given these continued model struggles and uncertainties, can justify no more than slight chance PoPs late week and into the weekend. Continued expectation is for a broad inch or two of rainfall through mid week, with uncertainty then very high beyond then. While this may prevent further deterioration of the ongoing hydrologic situation, it will not be enough to produce significant improvement and certainly not enough to resolve the drought completely. At this point, several inches of rain over multiple events will be needed to get us back to baseline. && .AVIATION (12Z TAF Issuance)... Issued at 540 AM EDT Sun Sep 22 2024 Impacts: - Convection including embedded thunderstorms will spread across the terminals after 12z before briefly diminishing after 04Z Monday - MVFR and briefly worse flying conditions in convection and also after 18z away from convection Discussion: A warm front will move across the terminals this morning followed by a cold front tonight. These fronts will interact with deep moisture and sufficient instability to result in scattered to widespread convection through the TAF period. MVFR and briefly worse flying conditions are possible in and away from convection. Winds will be less than 10 knots and shift from southwest to northwest in the wake of a cold front this evening and early overnight. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ UPDATE...Ryan SHORT TERM...MK LONG TERM...Nield AVIATION...MK