Sunrise 7:00 AM   Sunset 8:23 PM Moonrise 2:33 PM   Moonset 3:50 AM

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FXUS63 KLMK 190147 AFDLMK

Area Forecast Discussion National Weather Service Louisville KY 947 PM EDT Thu Apr 18 2024

KEY MESSAGES

* Strong to severe storms possible Thursday night. Highest risk of severe storms will be generally west of I-65.

* Much cooler weather this weekend. Next chance of rain arrives in the Tuesday/Wednesday timeframe.

MESOSCALE
Issued at 947 PM EDT Thu Apr 18 2024

A few discrete warms sector cells have been firing off ahead of the main convective line, which has been expected and picked up well in the earlier CAM runs. It appears these cells are popping up in an area of localized theta-e advection and deep moisture convergence axis, and underneath a pocket of positive vorticity advection. SPC Mesoanalysis suggest these storms are firing along a gradient of SBCAPE, but have struggled to become severe. Will keep an eye on these.

Severe thunderstorm line is charging across eastern Illinois at this hour, and is noticeably accelerating as the cold pool pushes it further east. At this pace, believe the line will be arriving into Dubois County by 0230z. ACARS sounding out of SDF does show some SBCAPE lingering, but thinking MLCIN will help weaken the line as it approaches the I-65 corridor by 04-05z. HRRR 00z data supports this too, with low level stable layer expected to help weaken this convective line in a few hours. Will need to keep tabs on additional convection across south-central KY later tonight though, where there is potential to remain unstable within the warm sector prior to the cold front arrival.

SHORT TERM /THROUGH FRIDAY/
Issued at 346 PM EDT Thu Apr 18 2024

Currently, satellite imagery is showing a warm front stretching to the northwest through southern Indiana and central Kentucky. This front arches to the west into a surface low in western Missouri. To the north of this front, dew points are in the 40s and 50s. To the south of the front, mid 60s, and as we head through the afternoon and evening hours, the surface low, part of a larger cold front extending to the north and south, will begin moving towards Indianapolis. This will cause the warm front and cold front to develop an inverted "V" look by 0z over southern Illinois, eastern Missouri and western Kentucky. Dew points over southern Indiana and central Kentucky will likely drop into the 50s as the region becomes better mixed.

As 1-2z approaches, the surface low will be moving from Illinois into central Indiana. The area under the aforementioned inverted "V" will see dew points in the mid 60s. Again, this is the area in between the warm and cold fronts. On the leading edge, the warm front will likely kick off convection over western Kentucky and southward while the cold front running through Chicago arches southward through southern Illinois. As these two lines continue eastwards. The front line could become the dominate line for southern part of the cold front over Missouri and could combine with the northern half of the cold front, or it could remain as two separate lines and join with the cold front over southern Indiana.
It doesn't make much of a difference, except some over central Kentucky could get one or two lines of convection.

The timing is going to help us from a severe weather standpoint.
Since the fronts won't move through until after sunset, an inversion is expected to develop and make any convection elevated. This will limit potential wind energy from reaching the ground. Overall shear is fairly weak. Think the current SPC outlook is a little bullish over our CWA

Winds tonight will remain out of the south to southwest around 5-10 mph. A few gusts around 30 mph will be possible as the line of convection passes, and as the cold front begins to move through during the morning on Friday, winds will quickly veer towards the north-northwest increasing cold air advection into the area. Winds tomorrow will stay around 10 mph as they gust to 15-20 mph.

WAA will keep temperatures warm tonight, only dropping into the 50s to low 60s. Tomorrow, the sun is expected to return, but CAA will limit temperatures to the 60s. A few in the Lake Cumberland region could hit the low 70s.

LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
Issued at 346 PM EDT Thu Apr 18 2024

Friday Night through Monday Night..

Dry conditions are expected Friday night and into Saturday as a surface high pressure system builds into the region with a dry zonal flow pattern aloft. A southern stream system may graze the far southern part of KY Saturday night and Sunday morning, but the latest trends in the data suggests a drier forecast may end up prevailing. Lows Friday night will dip into the upper 30s and lower 40s. Highs Saturday will be cool highs in the 60-65 degree range.
Lows Saturday night should be a bit cooler with lows in the upper 30s across much of the region. Areas south of the Cumberland Parkway may only drop into the lower 40s. Continued cool conditions are expected for Sunday with highs in the upper 50s to near 60.
Depending on cloud cover conditions Sunday night, we could see some patchy frost in southern IN and the KY Bluegrass region as lows dip into the mid 30s. Monday will see warmer conditions returning to the area with temps warming up into the mid-upper 60s.

Tuesday through Thursday...

Forecast confidence continues to increase in another chance of showers and storms coming into the region in the late Tuesday/early Wednesday time frame as a shortwave trough aloft moves through the region. The previous forecast of solid PoP coverage still looks good here. Temperatures through the period will warm into the upper 60s to the lower 70s with overnight lows in the low-mid 40s.

AVIATION /00Z TAFS THROUGH 06Z SUNDAY/
Issued at 744 PM EDT Thu Apr 18 2024

VFR conditions will deteriorate this evening as showers and thunderstorms approach the region ahead of a cold front. Expect impacts to ceilings and vis as thunderstorms roll through from west to east, first at HNB in the next few hours, and later tonight at LEX and RGA. The peak for convective activity will be from 02-09z tonight. After the storms pass, ceilings will lower to MVFR and likely below the 2k ft fuel alternate threshold near the pre-dawn hours. There appears to be a short window where ceilings could drop to IFR, so included a TEMPO group at all terminals for that as well.
We'll gradually improve to VFR conditions again by late tomorrow morning or early afternoon, with post-frontal winds from the north.

LMK WATCHES/WARNINGS/ADVISORIES
KY...None.
IN...None.

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