Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/30/21

Area Forecast Discussion
National Weather Service Louisville KY
1113 PM EDT Thu Jul 29 2021 .Mesoscale Update... Issued at 1111 PM EDT Thu Jul 29 2021 Isolated to scattered thunderstorms have filtered into our southern Indiana and Kentucky Bluegrass counties and are approaching the Ohio River. Activity thus far has remained sub-severe, though one storm currently along the Orange/Harrison (IN) county line has shown supercellular characteristics and has been watched closely. Activity over the next hour or so will likely remain isolated to scattered, but we could see some additional storms drift in from the north overnight along the cold front. The overall strength of the convection overnight still has the potential to become severe given some favorable instability and modest shear in place, but at least up to this point weak capping in the low levels has kept things from getting too out of control. Issued at 920 PM EDT Thu Jul 29 2021 Isolated to scattered storms are starting to develop or enter into our southern Indiana counties. Most of this activity has been non- severe, but toward Crawford County, Illinois, there was a supercell that produced a TDS via KVWX. The environment across our southern Indiana counties remains very unstable above a weak inversion (>4000 J/KG MUCAPE), so if/when storms can overcome it and tap into the unstable air, they could quickly become strong or severe. Earlier in the day, models hinted at broken lines of strong to severe storms pushing into our region during the overnight hours. The latest HRRR runs indicate much of this activity may stay isolated to scattered in nature for the majority of the night, and given the latest radar trends, think this could be a viable solution. Severe potential also looks like it could persist a bit longer than originally thought and affect portions of south-central Kentucky through 08z-09z. One concern with more discrete activity overnight would be a lesser threat for severe wind potential and a higher threat for large hail and isolated tornadoes in supercells. Thankfully, deep layer and low level shear weaken as you go toward southern Kentucky, so the highest threats for severe potential continue to be across southern Indiana and northern/central Kentucky. Issued at 658 PM EDT Thu Jul 29 2021 AMDAR soundings within the past hour have indicated a weakening of the cap in the 900-800mb layer with winds now taking on a more northwesterly component. KLVX has also detected a couple of rogue cells that developed, though they have struggled to strengthen given the weak capping still in place. This activity is not anticipated to become strong or severe. Over the next hour or so, we may continue to see an occasional rogue cell go up across southern Indiana and central Kentucky. Activity currently in central Illinois and Indiana along a weak surface boundary will begin drifting into our southern Indiana CWA counties between 00-01z. Additional activity along a cold front just to its north will filter into the region around or after 03z. Strong to severe storms will be possible with that activity as it drifts southward. Issued at 515 PM EDT Thu Jul 29 2021 Recent AMDAR soundings from SDF indicate a fairly impressive cap remains in place (~23C near 800mb). A look at SPC mesoanalysis pages and high-res model guidance of 900-800mb fields indicate a warm `nose` of temperatures stretching from the central Plains into the lower Ohio Valley resulting in the strong cap. Winds currently at these levels are generally out of the west or west-northwest, so temperatures in these levels should not change much in the very near term, which means the cap should stay in place and prohibit storm development. It`s not until we get closer to 00z that we begin to see winds in these levels shift more northwesterly as a trough sinks in from the north. Cooler temperatures aloft associated with the trough will advect in and help to break down and weaken the cap. Convection currently in central Indiana and Illinois will drift close or toward our area over the next several hours, and depending on how organized it is and if there are any outflow boundaries or cold pools associated with convection, it could be enough to overcome a weakened cap. Threat for strong to severe storms will likely occur after 00z and persist into the early morning hours. && .Short Term...(This evening through Friday) Issued at 320 PM EDT Thu Jul 29 2021 ...Strong to Severe Storms Possible this Evening... So far this afternoon temperatures have warmed into the upper 80s and low 90s as of 2 pm EDT. Dew points were just oppressive in the mid/upper 70s. This was producing heat indices around 100 degrees, mostly west and along I-65 where we have the higher dew point values. This heat and moisture has created a very unstable atmosphere which will remain in place as we go into the evening setting the stage for the development of strong to severe storms. The Storm Prediction Center continues to keep the northern third of our CWA (county warning area) in a slight risk for severe thunderstorms. The main threat being gusty damaging winds and torrential heavy rain. Afternoon mesoanalysis shows sfc cold front stretching across northern MO into northern IN over Lake Erie. Radar was showing scattered development just south and along the boundary. South of the front was strong to moderate instability with CAPE values across central KY and southern IN ranging from 2500-3500 J/kg east of I-65 to 3500-4500 J/kg to the west. Model soundings were showing dry air aloft keeping our DCAPE between 800-1000 J/kg keeping the main threat gusty damaging winds in the strongest storms this evening. Current hi-res model guidance is showing a slower solution in the development of scattered to broken convection this evening. Updated timing looks to drop a broken to scattered line of storms southward into our southern Indiana and north-central Kentucky counties between 9 PM- Midnight EDT and pushing southward into southern KY in the early morning hours. As the storms work to along and south of the Parkway, guidance has been consistent in showing the activity to diminish as it reaches the TN/KY border by day break. Tomorrow will feature cooler and less humid weather for the end of the week. Dew points will fall into the low/mid 60s by the afternoon with afternoon temperatures in the low to mid 80s north of the parkways and mid/upper 80s south. .Long Term...(Friday night through Thursday) Issued at 315 PM EDT Thu Jul 29 2021 The long term forecast will see only minor changes. On Saturday, as a shortwave/cold front drops south, trying to amplify the trough over the eastern CONUS, a few showers and thunderstorms will be possible. With most of the available moisture towards the CWA`s southwest, believe the best chances of precipitation will be on the southwestern side of the CWA Saturday night before fading Sunday. Rainfall totals are expected to range from a hundreth of an inch in our southeastern Indiana and northeastern Kentucky counties to around three quarters of an inch near Bowling Green. Some isolated areas could see higher amounts under heavy downpours. Moving into early next week, northwest flow with surface high pressure remains over the CWA. This will suppress moisture to the south and drop dew points into the 50s across the CWA by Tuesday. With this pattern and lack of available moisture, believe mostly dry conditions will prevail through the end of the work week. However, the GFS does try to form an upper closed low over the region on Wednesday. This would increase precipitation chances towards the end of the week, but for now, don`t believe this is likely. Plans should be based on a mostly dry comfortable week with highs in the 80s and low dew points. && .Aviation...(00Z TAF Issuance) Issued at 659 PM EDT Thu Jul 29 2021 A broken line of showers and thunderstorms are may develop tonight ahead of a cold front and push through southern Indiana and central Kentucky. If a storm impacts a terminal site, expect gusty winds and briefly reduced visibilities and ceilings. Drier air will filter in behind the front and winds will turn to the north. VFR conditions are anticipated in the wake of the storms for the remainder of the forecast period. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Mesoscale...DM Short Term...BTN Long Term...KDW Aviation...DM