Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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569 FXUS63 KIND 262206 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 606 PM EDT Sun May 26 2024 .KEY MESSAGES... - Another round of thunderstorms arrives tonight, especially south. - Some of these storms may be severe with damaging winds the primary threat. - Shower chances and cooler temperatures Tuesday-Wednesday - Dry and Seasonable Thursday and Friday - Rain chances on Saturday and Sunday && .MESOSCALE UPDATE... Issued at 606 PM EDT Sun May 26 2024 Latest LAPS data was showing the Wabash Valley through the Metro has rapidly destabilized owing to diabetic heating and that advection with SB CAPEs 1000 to 2000 J/kg. Deep and low level wind shear has also really ramped up in southwest flow aloft, ahead of the main trough, currently over Kansas. Meanwhile, messy setup at the surface with an outflow boundary from northeastern Indiana into eastern Kentucky and northern Tennessee. Meanwhile, a warm front was over north central Indiana and a cold front extended from western Illinois into the Ozarks. Hi-Res hodographs suggest there is a brief window of long curved hodographs with favorable SRH through 9 pm. However, visible satellite pictures were showing no evidence of agitated cu over central Indiana this afternoon. In addition, by far the best instability is well to the southwest across southeastern MIssouri and western parts of Kentucky and Tennessee. So CI may need to wait until after 00z as the CAMs suggest at which time the cold front gets closer. Any storm that would develop across central Indiana prior to then would have a potential to be severe with the combo of moderate to strong instability and deep and low level shear. After 00z, look for the bulk of the stronger to severe storms to be over southwestern sections. Storm movement will be SSE to 35 knots and quicker if a strong cold pool develops. With PWATs to 1.4 inches, and MRMS estimating around an inch and a half has already fallen, there is some concern for localized flooding over southwestern sections this evening. However, the convection is expected to quickly move through and be southeast of the area early overnight. Thus, the concern is tempered. && .SHORT TERM (This evening through Monday)... Issued at 234 PM EDT Sun May 26 2024 Rest of This Afternoon... Showers and lingering thunderstorms will continue to exit central Indiana to the east and north into mid-afternoon. Behind this, clouds will also gradually decrease from the south and west. Temperatures will be able to rebound some, especially southwest. Convective inhibition will persist for much of the afternoon as the atmosphere recovers from the previous convection. Without much of a trigger and with the inhibition, will keep PoPs low behind the initial line for much of the period. Later this afternoon, more convection will fire west of central Indiana. Latest hi-res models have been slowing down this convection`s arrival time into central Indiana, but will still increase PoPs higher into the chance category southwest by 23Z or so. Tonight... An upper wave will be responsible for the forcing that generates the convection to the west late this afternoon, and it will continue the forcing into the area this evening. Southwest winds at the surface and a continued moist flow at 850mb will bring in instability and moisture to the area. However, best instability will remain south of central Indiana, and the storms should turn into that fuel. Will go highest PoPs tonight in the south. Questions remain on whether the southern storms will rob enough moisture to keep the northern area from having much rain. With this possibility in play, will go lower PoPs north with higher uncertainty. The return of instability on southwest flow will keep the threat of severe storms across central Indiana this evening. The main threat will be across southern sections of the area where shear is best. Depending how fast storms turn southeast into the better instability, the threat could be farther south. Will monitor closely, but stay weather aware. After the initial complex of storms moves out of the area, additional, weaker convection may develop as a cold front moves into the area. Will keep PoPs going through the night. Monday... Most forcing will be east of central Indiana by 12Z Monday, but enough may linger east for a few showers in the morning. Will keep some slight chance PoPs there. Otherwise, any forcing from the next upper wave should wait until Monday night, so will go dry during the afternoon all areas. Temperatures will get into the mid 70s for highs. && .LONG TERM (Monday night through Sunday)... Issued at 234 PM EDT Sun May 26 2024 Tuesday and Wednesday - Models show strong ridging aloft over the Rockies and a broad upper trough over Ontario and the Great Lakes. This cyclonic flow aloft looks to impact Central Indiana on Tuesday and Wednesday as several upper level forcing features pass within the flow on Tuesday, Tuesday night and Wednesday. Meanwhile within the lower levels, surface low pressure over the Great Lakes on Tuesday is expected to push toward Quebec by Tuesday. This feature looks to keep cyclonic flow across Central Indiana on through this time with several weak surface trough axes looking to pass. Deep moisture fails to arrive, especially given our northwest continental flow, but forecast soundings show some weak instability. Thus at least a small chance for showers and storms seem reasonable. Again, washout days are not expected, but pop-up showers with diurnal heating and weak forcing aloft cannot be ruled out yet. Cooler northwest flow will allow highs to remain below normal, within the lower to middle 70s. Thursday and Friday - The previously mentioned upper ridge of high pressure is expected to build east across the Great Lakes and Ohio Valley on Thursday through Friday night, with a ridge axis passing across Indiana on Friday Night. An associated area of strong surface high pressure will also pass across our region. Forecast soundings show a very dry column through this period indicative of ongoing subsidence. Thus mostly sunny days and mostly clear nights will be expected. Again southerly return flow does not begin until Friday Night. Thus temps will remain below normal with highs in the middle 70s. Saturday and Sunday - The upper ridge and surface high are expected to exit east on Saturday, allowing for southerly warm and moist gulf flow to Indiana. Aloft, a deepening trough is expected to be found over the plains states, providing southwest flow aloft and ejecting embedded forcing toward central Indiana within the flow. Mid levels suggest sufficient moisture available as a broad area of saturation is shown to pass across the region. Timing at this point appears a bit uncertain, thus ongoing pops through the period look reasonable. Slightly warmer temperatures will be expected on Saturday as southerly flow is predominate, but rain and a more westerly flow on Sunday may result in cooler highs. && .AVIATION (18Z TAF Issuance)... Issued at 140 PM EDT Sun May 26 2024 Impacts: - Another round of storms at mainly southern sites 00-05Z - Winds gusting to around 20kt this afternoon and again Monday - MVFR ceilings develop overnight Discussion: First area of showers and storms will be east of the TAF sites by valid time, with VFR ceilings behind it. Winds may vary between SE and S for while this afternoon and gust to around 20kt. Another thunderstorm complex looks to move across mainly the southern sites this evening, with MVFR and worse possible in convection. After this exits, scattered showers will linger for a while, followed by MVFR ceilings. Winds will become west. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ MESOSCALE...MK SHORT TERM...50 LONG TERM...Puma AVIATION...50