410 FXUS63 KLMK 102349 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 749 PM EDT Thu Apr 10 2025 ...Updated Aviation Discussion... .KEY MESSAGES... * Isolated strong to severe storms will be possible this afternoon and evening, especially across south-central Kentucky. * Drier conditions with warming temperatures are expected this weekend. * A low-medium confidence chance for strong storms arrives next Monday. Gusty winds and hail are the primary severe threats. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 337 PM EDT Thu Apr 10 2025 An upper level shortwave will continue to rotate southeast over the Mid-MS and Lower OH Valleys this afternoon, bringing very cold (-26 C) mid-level air over the region. Though low-level moisture is modest, strong insolation has warmed sfc temperatures into the mid 60s to lower 70s. MLCAPE appears set to peak at around 1000 J/kg over central KY and far southern IN through mid-evening. A cluster of convection has already developed along a weak cold front in southern IL and southeast MO, with an isolated thunderstorm now over western KY ahead of the main cluster. This activity will spread east-southeast through central KY this evening. Additional updrafts may develop along the convective outflow/cold pool, with storms increasingly organizing into a short line. Deep-layer shear of 25-30 kts is marginal for storm organization. But given the very steep lapse rates through a deep layer, and very cold temperatures aloft, the environment appears supportive of both isolated damaging wind gusts and isolated large hail. Storms will be fairly slow moving to the E/SE due to weaker steering flow aloft. Deep-layer shear is strongest (30 kts) across south-central Kentucky, with notably weaker mid-level winds further north. Therefore, have coordinated with SPC and neighboring NWS offices on a Severe Thunderstorm Watch for south-central KY. This area is more favorable for updraft organization, and therefore large hail/wind potential. Locally strong gusts and hail will still be possible north of the Watch area. Convection will weaken after 00Z due to waning instability, but scattered showers will remain possible overnight. The mid/upper level trough axis rotates overhead tonight into Friday morning, with lingering shower activity confined to just south-central KY after 12Z Friday. Friday morning will be cool and cloudy, with a north wind and lows around 40-45 degrees. Clouds will take their time clearing Friday afternoon and evening, but the trend looks positive here as ridging begins to nose in from the west. Overall, looks like a partly cloudy afternoon with highs in the 50s. The first part of the weekend looks cool and pleasant. High pressure gradually builds east across the area through Saturday night. This does raise concerns for frost both Friday night and Saturday night, which could impact sensitive early vegetation. Lows in the low to mid 30s look possible for much of the area. Other than the chilly start, Saturday looks like a nice Spring day with afternoon highs in the mid 50s to around 60 degrees. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Issued at 337 PM EDT Thu Apr 10 2025 Sunday and Sunday Night... A warming trend is expected during the second half of the weekend as upper-level ridging builds over the Mississippi and Ohio Valleys. A shortwave disturbance moving into northern Plains on Sunday will promote sfc cyclogenesis over the upper MS valley. Between this low pressure and high pressure over the northern Gulf, southerly flow should boost temperatures into the mid-to-upper 60s and lower 70s across the region Sunday afternoon. All in all, Sunday should be a pleasant day weather-wise with light south winds and mostly sunny skies. Sunday night, a west-southwesterly LLJ will develop over the region ahead of the approaching mid-level shortwave. This will bring some moisture into the area, and clouds will increase Sunday night. However, moisture is not expected to be nearly as rich as last week`s system, with ensemble mean PW values rising to around 1-1.1" Monday morning. Persistent southerly flow overnight Sunday night will keep temperatures milder, with lows only expected to fall into the 50s in most locations. Monday and Monday Night... Monday into Monday night, the aforementioned upper trough and sfc front will move through the Ohio Valley. In previous model runs, there were minor timing discrepancies between the different ensemble suites, with the GFS generally a bit slower than the ECMWF. Initial analysis of the 12Z data suggests better model agreement on timing of FROPA, which will have an impact on shower/storm chances Monday afternoon and evening. Forecast soundings for next Monday afternoon show much of the moisture increasing in the low levels, with cooler and drier air aloft allowing for steep mid-level lapse rates within an elevated mixed layer. As the previous discussion noted, hodographs show primarily speed shear, and given the EML and steep mid-level lapse rates/dry air, would expect hail and gusty winds to be the main severe threats. There is quite a bit of uncertainty with this event, as the overlap between the best forcing and the best instability is quite narrow, and there will be quite a bit of mid- level capping to overcome. Fortunately, this system will be quick-moving, with ensemble mean QPF amounts only around 0.10-0.25" at this time. As a result, any additional rainfall Monday is not expected to exacerbate ongoing hydro/flooding issues. Tuesday through Wednesday Night... Behind Monday`s system, upper troughing will settle across the eastern CONUS with NW flow moving over the Ohio Valley. This should bring another period of relatively calm weather with cold advection dropping temperatures back below normal on Tuesday. Gusty winds would be expected on Tuesday, especially given steep low-level lapse rates in the post-frontal environment. Otherwise, dry weather is expected through next Wednesday, with the next potential system arriving next Thursday. && .AVIATION /00Z TAFS THROUGH 06Z SATURDAY/... Issued at 748 PM EDT Thu Apr 10 2025 Sct SHRA and TSRA have developed along a weak frontal boundary and ahead of an upper level shortwave trough. This activity will continue to drift ESE with time. Isolated TSRA will remain possible through 03-04Z, but expect convection to weaken diurnally after 00Z. SHRA will continue to pivot cyclonically across mainly SDF/LEX/RGA into the overnight hours. Winds will veer N/NNE overnight into early Friday morning. Low-end MVFR and IFR ceilings are expected develop across the area between 06-12Z Friday. Ceilings should lift/scatter back to VFR early afternoon. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...EBW LONG TERM...CSG AVIATION...EBW