Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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943 FXUS63 KIND 211924 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 324 PM EDT Fri Jun 21 2024 .KEY MESSAGES... - Hot weather persists today and Saturday - Chance of showers and storms late Saturday night into Sunday - Potentially very hot on Tuesday - More thunderstorms possible Tuesday into Wednesday - A brief respite from heat and humidity late next week && .SHORT TERM (This evening through Saturday)... Issued at 323 PM EDT Fri Jun 21 2024 Rest of Today and Tonight... Diurnal cu has developed across central Indiana, with convective temperatures now met as of early this afternoon (88-89). This 30-50% cloud cover should continue through the late afternoon, with a slow decline this evening within surface cooling before mostly clear conditions become the rule overnight. Surface temperatures have plateaued some as the PBL has become well mixed. However, temperatures should begin to increase again over the next few hours with surface fluxes increasing in an already well mixed airmass. Current observations show temperatures in the upper 80s, with highs currently expected to be between 93-95 across the region. Overnight temperatures will once again efficiently cool as the PBL becomes decoupled, pushing surface temperatures towards dew point values. Still, 25-30 degree dew point depressions will help mitigate the ability for surface temperatures to reach saturation in most areas; outside of water ways and well irrigated fields. With this in mind, the current expectations is for morning lows in the low 70s. Tomorrow... Similar conditions will exist tomorrow as central Indiana remains within a heat dome underneath anomalously high heights. This should keep temperatures in the low to mid 90s over much of central Indiana. Modest mid-level lapse rates will also still be present, providing the necessary parameters for diurnal cu development once again tomorrow afternoon. The main difference will be increasing low to mid level winds out ahead of an approaching low level wave. This wave will be the main culprit for convective development over the Great Lakes region tomorrow, but will also provide an uptick in surface winds over central Indiana. An increasing 900-800mb pressure gradient ahead of the wave should also lead to modest gusts in the afternoon once the PBL mixes up into the 15-20kt LLJ. The aforementioned upstream convection will provide low rain chances late on Saturday, but the bulk of this threat is likely not to reach the Indiana border til will into Saturday night. && .LONG TERM (Saturday night through Friday)... Issued at 323 PM EDT Fri Jun 21 2024 The long term forecast features a couple of opportunities for heat relief, at least one or two additional stiflingly hot days, and a couple of opportunities for potential convection, some of which may be organized and present at least a low potential for strong to severe storms. The large scale ridge currently over the region will steadily retrograde into the southern Plains and Desert Southwest over the next few days into next week, providing some heat relief but also placing us in a potential zone for one or more rounds of convection. Conditions will remain quite warm and humid, but slightly less so as the ridge moves. The first potential for convection comes tomorrow night into Sunday as a system cresting the ridge moves into the region, and frontal forcing along with ample upstream destabilization will allow for some organized convection to develop late in the day on Saturday, progressing downstream Saturday night. Diurnal timing is somewhat unfavorable and overall shear is relatively weak, but depending upon the strength of the initial convection and subsequent upscale growth/cold pool development, a localized damaging wind threat cannot be ruled out as storms, which may be weakening, move into the area late Saturday night. The storms, or associated boundaries, may promote redevelopment/reintensification during the day on Sunday, again with a localized damaging wind threat. Uncertainties are plentiful, and current day 2/3 marginal risks from SPC are reasonable. The next opportunity looks to come primarily Tuesday evening into Wednesday. While there will also be synoptic scale support for this round, this looks to be a bit more analogous to the traditional "ridge rider" scenario, with very strong instability/modest shear contributing to the development of one or more QLCSs, which then drive south/southeastward into the instability axis Tuesday evening into Wednesday. Uncertainties increase with time, particularly given that prior days` convection will significantly influence subsequent days, along with typical guidance spread, but experimental CSU machine learning guidance is highlighting late Tuesday into Tuesday night as a time frame to watch for an organized severe threat. Sunday night into early Tuesday and late Wednesday and beyond appear to have good chances of remaining dry for now. Temperatures will moderate somewhat with the movement of the ridge, but humidity will remain high until late in the week, particularly ahead of the boundaries that will move through the region as moisture pools. This will promote continued, but mostly typical, summertime heat, with the possible exception of Tuesday, when depending upon convection timing and associated cloudiness, highs could reach back into the low to mid 90s with dewpoints approaching or exceeding 70, producing afternoon heat indices in the low 100s. NBM`s hot bias, particularly when dealing with the aforementioned potential failure modes, necessitates some adjustment to highs Tuesday, but regardless, we anticipate sticky, uncomfortable conditions that day, possibly followed by severe storms. Some relief may come late in the work week, particularly in the form of lower dewpoints, but unfortunately as we move toward the end of the month, this may be relatively short lived. && .AVIATION (18Z TAF Issuance)... Issued at 202 PM EDT Fri Jun 21 2024 Impacts: - VFR conditions expected through the TAF period. Discussion: Conditions will remain VFR through the entire forecast period as high pressure aloft continues to keep tranquil weather at all TAF sites. Light surface winds out of the W/SW will continue through the evening before become calm overnight. Winds will pick up again tomorrow with gusts potentially in the mid to late afternoon. Sct/bkn mid-level clouds around 5-6 kft this afternoon will dissipate this evening, with sct mid-high clouds overnight && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Updike LONG TERM...Nield AVIATION...Updike