Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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819 FXUS63 KIND 031610 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1210 PM EDT Mon Jun 3 2024 .KEY MESSAGES... - Warmer today/Tuesday periodic thunderstorm chances. The best chances will be Wednesday. - Below normal temperatures in the 70s late week into the weekend && .FORECAST UPDATE... Issued at 919 AM EDT Mon Jun 3 2024 An upper ridge will move from the upper Ohio Valley to the Appalachians by this evening. Meanwhile, upper impulses in southwest flow will generate to mid and high clouds and cu development progs suggest scattered diurnal cu is likely as well. Otherwise, their will be enough sunshine to go along with southerly winds for temperatures to bounce back to the middle 80s during peak heating. && .SHORT TERM (Today and tonight)... Issued at 236 AM EDT Mon Jun 3 2024 Early This Morning... Late evening cirrus has dissipated, with mid-lvl water vapor indicating the channel is knocking on the door steps of Central Indiana. The big concern overnight revolves around potential for fog development. Dewpoints are still in the low 60s for much of the area, and we never observed good afternoon/diurnally driven mixing to provide any subsidence once the shallow stratus deck departed. With a weak isallobaric gradient overhead from weak ridging, it would appear favorable for seeing patchy fog to develop. Earlier in the evening KIND VWP would equally support this with most targets within 1000ft agl being less than 5kts; however, since 3Z we are seeing targets return at 2-5kft agl from the southwest at roughly 10- 15kts. This would suggest we may be on the backside of the weak ridge, and could inhibit the fog potential due to induced friction within the boundary layer. While this appears to be the case for Indy metro and points west/northwest, the same may not be for the southeast forecast area. Surface OBS are indicating a few points are seeing fog develop with some reduction to VSBYs being observed; however, the duration for the lowest VSBYs does appear to be minimal which is supportive of the shallow ground fog type and easily fluctuates with any little bit of wind. Have opted at this time to issue an SPS to highlight the nuisance hazard that could be encountered early this morning across Central Indiana. Should conditions deteriorate in the next few hours we may need to go with a dense fog advisory, but at this time that does not appear to be needed. Remainder of today... Once sunrise hits, we should observe a steady diurnal swing with temps. The caveat will be the increased heat capacity to surface parcels due to the continued moist nature of the boundary layer. So that should slow the rate of warmth late morning, but with minimal cloud cover overhead and a weak gradient in the pressure fields, temps should easily be flirting with 80 degrees by noon or shortly after. Then through the afternoon hours temps will continue to warm, but expect a cirrus shield to be arriving from the west as the axis of higher mid-lvl moisture begins to drift east. So expect a dry day, although there is a possibility that a few isolated showers could develop late in the afternoon for the far west/southwest portions of Central Indiana. Confidence is very low in this scenario though. Tonight...Slowly thickening cloud cover aloft from west to east overnight. Guidance has continued to hint that some very weak instability could nudge east overnight, and coupled with the moist layer overhead could translate into an isolated shower/thunderstorm. Have held onto low POPs as not all solutions are in agreement which suggests a lower confidence forecast for precip tonight. With thickening clouds expect temps to not radiate much below the middle 60s. && .LONG TERM (Tuesday through Sunday)... Issued at 236 AM EDT Mon Jun 3 2024 Highlights of extended continue to be the active weather mid-week, with the anomalous shortwave that parks itself over the Great Lakes region later in the week. Tuesday... Some amplification to the 500mb wave ahead appears to be favored for the Ohio Valley. With any amplification to heights, it should aid the lower levels that remain moist with a channel of water vapor present from the West GOMEX stretching north through the Western Ohio Valley into the Great Lakes. Guidance is still leaning towards perhaps weak mid-lvl diffluence in the morning, but the downstream ridge should be drifting east and allow this moist channel to arrive across Indiana by afternoon hours. As a result there does appear to be some marginal instability, but nothing organized from a vorticity maxima or presence of robust shear, so at the moment feel that any convection should not grow upscale or more organized within the moist column. In addition to the precip chances Tue increasing, it does appear dewpoints will equally be elevated in the mid/upr 60s and likely result in a humid afternoon with max apparent temps nearing 90. The wildcard will be if upstream precip develops earlier in the day and helps introduce solar shielding by midday and holds temps down in the low 80s. Tue ngt-Wed... there continues to be some disagreement amongst guidance with respect to timing/placement of an upstream developing shortwave. The 500mb flow does appear to be quasi-zonal, which should help to shove the overhead amplified ridge east and as a result increase the precip chances overnight into Wed. Parcels will continue to be influenced by a warm/moist southerly flow, which will only further aid in perhaps more organized precip coverage but the timing appears to be around daybreak Wed. This will all hinge on the upstream arrival to the shortwave. Should the ridging persist longer, this will likely delay the precip channel until later Wed and also produce a more humid/warm day Tue. Subsequently it could also elevate the surface instability Tue aftn/eve, so several elements remain in place. As Wed progresses, a few things will be ongoing further upstream as well as over the Central CONUS. Guidance for several days has continued to place a shortwave sliding along the Northern CONUS while further upstream a steadily growing ridge should continue to amplify. Viewing the DESI 500mb/vort for mid-week and confidence remains high in placement out west of a robust ridge, which should result in a long trough period for the Great Lakes region and further support the broad vort max providing added clouds and precip chances to the Ohio Valley through weeks end. Thur-Sat...With a northwest flow arriving later in the week, the current projection is that the placement to the upper level shortwave will be displaced to the north of Indiana and perhaps far enough that precip coverage will likely be north/northeast. Ensembles also lean towards weak lower lvl ridging, which could assist with subsidence at the surface and pleasant temps in the 70s for Thur/Fri. && .AVIATION (18Z TAF Issuance)... Issued at 1210 PM EDT Mon Jun 3 2024 Impacts: - Thunderstorms and related MVFR flying conditions possible after 10z-12z Tuesday Discussion: VFR flying conditions are expected the bulk of the TAF period, however thunderstorms are possible by Tuesday morning. That said, expected coverage is too low to mention in the TAFs. Winds will be from the south less than 10 knots. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...MK SHORT TERM...Beach LONG TERM...Beach AVIATION...MK