Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/16/21

Area Forecast Discussion
National Weather Service Louisville KY
929 PM EDT Thu Jul 15 2021 .Mesoscale/Forecast Update... Issued at 929 PM EDT Thu Jul 15 2021 Convection has diminished considerably in the last hour across much of the region. Only remnant activity is is over our far northern counties of southern Indiana where residual outflow dominated showers continue to press east. These showers should continue to diminish due to the loss of instability and subsequent stabilization of the boundary layer. In general, we expect a lull in the precipitation over the region for the next several hour. After midnight, convection will probably re-enter our northwest CWA as ongoing convection out across central MO/IL works east southeast. Current forecast has this well in hand for the overnight period. Will be making just a few tweaks and adjustments to the grids and have an updated forecast package out by 945 PM EDT. Issued at 538 PM EDT Thu Jul 15 2021 Couple of areas of strong convection continue to push eastward across central Kentucky this afternoon. First batch was located up over the eastern Bluegrass region (Harrison/Bourbon/Nicholas counties). These storms remain sub-severe with wind gusts of 30-35 MPH, heavy rainfall, and frequent lightning. Earlier storms moved through this region and these storms trained over it. For that reason, we have small Flood Advisory in place for the next few hours. Most likely will see some minor impacts with this rainfall with creeks and streams going to bankfull along with poor drainage areas flooding. As seen in recent days, much of this runoff will drain off fairly quick after the storms move out of the area. Localized rainfall rates of 1-2 in/hr will be possible. Second area of storms seems to be on the increase. These storms were located from near Lawrenceburg and extend southward to near Campbellsville. Storms are moving through an environment of 2000- 2500 J/Kg of MLCAPE. A small corridor of 900-1000 J/Kg of DCAPE is just downstream of this activity. Effective shear remains very weak with values of less than 20kts. Nonetheless, robust updrafts keep ongoing feeding off the localized area of instability here. Current thinking is that strongest storms will remain on the north end of this cluster and will affect portions of Anderson/Mercer/Washington Counties over the next hour. Should the storms hold together, they could affect the Lexington Metro. However, earlier convective activity may have eliminated a bit of the instability over that way. Main threats with the Anderson/Washington/Mercer activity will be wind gusts of 30-40 MPH, heavy rainfall, frequent lightning, and a small risk of sub-severe hail. A special weather statement is in effect for this cluster of storms, but will continue to monitor trends over the next hour. && .Short Term...(This evening through Friday) Issued at 310 PM EDT Thu Jul 15 2021 Regional radar mosaic shows very isolated showers popping up across the region as sfc temperatures exceed convective temperatures. KY Mesonet obs show temps mostly in the upper 80s, and the SDF heat island in full effect with 91F so far. Model soundings seem to have a good handle on current conditions compared to latest AMDAR sounding data from SDF, which continues to show a strong 600mb inversion overhead. Expect this mid-level warm layer to persist though this afternoon and evening, but should eventually erode by the overnight hours. For the rest of this afternoon, expect to continue to see isolated shallow showers. Will keep a low chance PoP in before 00z for the entire CWA, but most folks will stay dry. Could have a few rumbles of thunder mixed in, but the inversion should be enough to cap tall vertical cloud growth. For tonight, upper shortwave trough currently across Kansas will shift eastward across Missouri, resulting in the southeastern US ridge to weaken and push further east. A secondary sfc low will develop across Missouri by tomorrow morning and track to the NE along the I-70 corridor. As a result, tightening low level pressure gradient will develop a LLJ, with 850mb winds expected to be 20- 35kts. As the SW LLJ noses into our region, scattered convection will be moving in from Illinois ahead of the slow moving sfc frontal boundary tonight and into tomorrow. SPC holds a Day 2 Marginal Risk across our northern half of the CWA for tomorrow, which seems well placed. CAMs are hinting at some possible organized convection tomorrow afternoon and evening, most likely across souther IN under the 850mb jet core. Temperatures should breach ConvT again, with highs primarily in the upper 80s and low 90s. Instability could reach 1000-2000 J/kg of MLCAPE during peak daytime heating, and effective bulk shear values between 20- 30kts. With PWATs also expected to be 2.10+", torrential rain rates with any training or slow moving storms would create some localized flash flooding hazards. Organized convection could also pose a threat of damaging winds and frequent lightning. .Long Term...(Friday night through Thursday) Issued at 240 PM EDT Thu Jul 15 2021 Friday Evening through Sunday...By Friday evening, the surface boundary will be stretched SW-NE across central IL/IN and into the lower Great Lakes with ongoing convection out ahead of the boundary, affecting our area in southern Indiana and central KY. The OH Valley`s position between Atlantic ridging and the upper trough will result in deep SW flow with PWATs around 2.00 inches. GEFS/GFS IVT continues to advertise moisture maxima remaining to our north, but model soundings continue to show saturated columns with tall, skinny CAPE profiles and high RH throughout the low to mid levels. Expect to see some efficient rainfall with this activity with localized flooding concerns being the main hazard of concern given parallel nature of steering flow to boundary positioning. Mitigating factors will include dry antecedent conditions and progressive nature of individual cells. Will just have to watch for training. And given the weak shear and moderate to high CAPE, expect low-end severe chances with pulse storm modes most likely. Diurnal enhancements will result in most rainfall accumulation taking place Friday evening and again Saturday afternoon. And as the boundary drops south through central KY on Sunday, expect to see lower PoPs across southern Indiana. Monday and beyond...Models continue to show Omega Block over the western and central CONUS, which will place the OH Valley under NW flow. Expect mostly dry conditions throughout this period. Thickness values slowly increase through the week so expect high temps in the mid 80s to increase to upper 80s by Thursday. && .Aviation...(00Z TAF Issuance) Issued at 730 PM EDT Thu Jul 15 2021 VFR conditions will remain into this evening. Models are showing some showers along a surface trough ahead of the front starting around 6Z at HNB and sinking southeast to LEX around 11Z. BWG should not be affected by these showers overnight. Most of tomorrow should remain dry until later tomorrow evening when the surface front pushes southward and along with it, a line of showers and storms. Timing confidence on this is low, so PROB30s are not mentioned in this TAF cycle. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Mesoscale.....MJ Short Term....CJP Long Term.....CG Aviation......SRM