279 FXUS63 KLMK 201033 AFDLMKArea Forecast Discussion National Weather Service Louisville KY 633 AM EDT Sat Sep 20 2025
...Updated Aviation Discussion...
.KEY MESSAGES...
* Mainly dry and unseasonably warm today with highs in the upper 80s and low 90s.
* Rain chances increase during the day Sunday with scattered showers and thunderstorms. Some storms may become strong, with gusty winds and hail possible.
* Daily rain chances through next week. Beneficial rain ranging from 2.0" to as high as 3.50" along and north of the Ohio River by Friday afternoon.
&&
.SHORT TERM /THROUGH TONIGHT/... Issued at 314 AM EDT Sat Sep 20 2025
Troughing is moving east into the Midwest and Ohio Valley this morning. The lower Ohio Valley will just be on the periphery of the larger troughing through the short term.
Through the day, convective debris clouds and a thin afternoon Cu field will work over the region. Expecting to see high temperatures in the upper 80s and low 90s. In the late afternoon and into the evening hours, some showers and storms may develop to the west of the region, but will quickly dissipate as they encounter dry air still in place over the region. Some sprinkles or light rain isn`t ruled out over the far western areas.
In the overnight hours, vorticity traveling along the upper troughing will approach the region from the northwest. Additionally, a 25-30kt LLJ will overspread the Ohio Valley, which will usher in better moisture. This will develop scattered showers and storms northwest of the region. In the early morning hours, we will begin to see some showers move into southern Indiana. The majority of the night will remain dry with increasing cloud coverage. Expecting to see low temperatures in the low-to-mid 60s and some cooler spots in the upper 50s.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 314 AM EDT Sat Sep 20 2025
Sunday...
Troughing will continue to slowly shift east and mostly remain to the northwest of the region on Sunday. By Sunday afternoon, southerly flow will have ushered in PWATs around 1.6 inches. This moisture coupled with continued vorticity streaming over the region will allow for showers and storms to develop. Best chances for showers/storms will be over the northwestern half of the region. Forcast soundings show modest CAPE (1500-1700 J/kg), weak unidirectional shear, and modest lapse rates. As storms develop, we could see some stronger storms capable of gusty winds and hail. Best timing is Sunday late afternoon through the evening. HREF LPMMs show a few bullseyes of about 2.0 inches over southern Indiana and along the Ohio River.
In the overnight, a 25-30kt LLJ will once again overspread the Ohio Valley and help to promote overnight showers and few storms. Storms will remain limited given the weak instability profile, though elevated convection is possible.
Monday through Tuesday...
The main trough axis will slowly swing through the region Monday afternoon and evening. Forecast soundings continue to show modest CAPE and increased shear. Showers and stroms will move through the region Monday afternoon through the evening, where some storms could become strong to severe.
On Tuesday, upper flow becomes messy and mostly zonal with a continued vorticity stream from a developing cut-off low over the central Plains. Showers and storms will remain over the region on Tuesday.
Wednesday - The End of the Work Week...
The cut-off low over the central Plains will begin to work eastward and interact with the troughing in place over the Great Lakes region. Some long range guidance is suggesting these two features eventually creating a Fujiwhara interaction over the mid-Mississippi and Ohio Valleys. This Fujiwhara interaction would then develop a surface low pressure system that moves through the region. During this time, we will see continued shower and storm chances and near normal temperatures.
Precip Chances Through the Long Term...
Over the last several days, we have seen guidance trend with increased precipitation. Each day we have seen probabilities of (much needed) rainfall increase. LREF probabilities now stand at 40- 60% of exceeding 2.0 inches of rainfall, and a 30% chance of exceeding 3.0 inches of rainfall (mostly over the northwestern half of the region). Current forecast shows a widespread 2-3 inches, with locally higher amounts over the northwestern half of the region.
&&
.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/... Issued at 632 AM EDT Sat Sep 20 2025
Convective debris clouds stream over the region this morning and winds are calm or light and variable. By mid-morning, winds will begin to pick up out of the SSE around 5-7kts. In the afternoon, a thin Cu field around 6-8kts will likely develop. In the overnight, some isolated to scattered showers and storms will approach the region from the west. These will begin to dissipate, though showers are possible at BWG/HNB.
&&
.LMK WATCHES/WARNINGS/ADVISORIES... KY...Air Quality Alert until midnight EDT tonight for KYZ029>031. IN...Air Quality Alert until midnight EDT tonight for INZ077>079- 090>092.
&&
$$
SHORT TERM...SRW LONG TERM...SRW AVIATION...SRW
NWS LMK Office Area Forecast Discussion