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FXUS61 KILN 071456 AFDILN

AREA FORECAST DISCUSSION National Weather Service Wilmington OH 1056 AM EDT Tue May 7 2024

SYNOPSIS
Several rounds of showers and storms are expected through Thursday amidst a continued warm and humid pattern. Slightly cooler air will filter into the region late in the week, with slightly drier conditions also expected. However, periodic chances for showers will likely linger into the weekend.

NEAR TERM /UNTIL 6 PM THIS EVENING/
Morning update trended the forecast towards HRRR/RAP blended into current forecast. This seemed on track for T/Td and accounted for line of storms crossing the CWA this morning, with a break behind it. While placement and occurrence of storms in the airmass this afternoon/evening remains in question, the model blend noted above looked to capture probability of rain/storms if not relatively well then well within reason.

Weak showers running nw-se that tail off over Warren County have a warm frontal appearance. The airmass difference here is an uptick in dewpoints behind it.

Parameters of significant shear and instability remain in place this afternoon for severe weather. This is an all-mode severe weather threat with damaging winds, large hail, isolated flooding, and tornados. Tornado parameters per SPC and some AI forecasts have the entire CWA with a potential of significant tornados >EF2. The AI enhances a more narrow corridor running sw-ne through Cincy metro area, curving northward into Dayton metro area.

Previous Discussion: Vigorous low pressure over the northern Plains will lead to a moist southwest flow of air across the Ohio Valley today. A decaying band of showers with isolated thunder is expected to slide east through the region late this morning through early this afternoon. Severe storms are not expected with this band.

As a shortwave is ejected northeast from the southern Plains into the Ohio Valley, an increase in mid- level flow and backing low- level winds will be seen in the vertical profile by later in the afternoon. A surge in warm, humid air will likely occur just ahead of the shortwave's arrival. Forecast soundings from the HRRR are concerning, with surface CAPE late this afternoon into the early evening approaching 2,500 J/kg and effective shear reaching around 60 knots. Curved hodographs lead to effective SRH exceeding 200 m^2/s^2.

The latest guidance suggests a less forced environment late this afternoon, so scattered, discrete supercells are expected.
All hazards appear likely with these storms. High temperatures will reach into the upper 70s to lower 80s.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/
A cold front associated with the shortwave will shift east across the local forecast area late this evening through midnight. While hodographs are a bit less curved for this period, an increase in forcing leads to higher coverage of thunderstorms, and likely a more organized linear mode. Can't rule out some embedded supercells as well based on persistent bulk shear ahead of the front.

The shortwave will exit to the east late tonight, leading to a quieter conditions extending into Wednesday. Bright May sunshine allows high temperatures to exceed 80 degrees across the middle Ohio Valley. We may see some increase in cloud cover late in the period as another shortwave begins to eject northeast into the middle Mississippi Valley.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
A warm frontal boundary will be draped along the Ohio River early Wednesday evening, extending east from a surface low over the mid Mississippi Valley. As the low tracks east Wednesday night, the boundary will begin to lift slowly north across southern portions of our fa. There remains some uncertainty with just how far the front will make it, along with the better instability, but the 00Z models appear to have trended everything a bit farther to the south. Still, expect to see showers and thunderstorms overspread the region Wednesday evening and continue into the night as the surface low moves through our area.

With very favorable shear and an instability gradient along the boundary, some severe storms will be possible, with the best chances mainly along and south of the Ohio River, closer to the better instability. Damaging wind and large hail will be the main severe threat, although an isolated tornado will also be possible. Also, with the potential for training storms along the boundary and PWs in the 1.5 to 2.0 inch range, there will be a heavy rain/flood threat, especially across southern portions of our area Wednesday night. Pcpn will taper off later Wednesday night into Thursday morning as the low moves off to the east.

An upper level trough will settle in across the Great Lakes and Ohio Valley heading into the weekend and into early next week.
A series of embedded mid level short waves rotating through the trough will bring additional chances for showers and a few thunderstorms each the day, especially Saturday afternoon and evening. Temperatures will be seasonably cool through the weekend with highs mostly in the 60s. More seasonable temperatures will return on Monday with highs in the low to mid 70s.

AVIATION /15Z TUESDAY THROUGH SATURDAY/
Lingering MVFR vsbys at CVG are expected to break up in the next 2 hours with low clouds scattering out underneath an overcast mid deck aoa 8kft. Line of showers west of the region will hit CVG/LUK/DAY around 17Z, ILN 18Z, and CMH/LCK 19Z. A lull in the thunderstorms is expected, then daytime heating and increasing instability with backing winds and a bump in low level moisture will promote a second round of storms, some severe this late day and early evening. Storms in this later environment will be more discrete and scattered versus coming in as a line, so VCTS seemed to be the better forecast for everyone attm. Storms exit to the south-southeast, first at DAY around 03Z, then by 05Z at the remaining TAF sites.

Outside of thunderstorm activity and this morning's low clouds, ceilings should remain VFR, but will amend if this is appears to not be the case as necessary.

Clouds will begin to decrease after 06Z as the weather system exits to the east. Will need to watch for stratus/fog development in the pre-dawn hours if the clouds clear early.

OUTLOOK...Thunderstorms will be possible late Wednesday into Wednesday night. MVFR/IFR CIGs are possible Wednesday night into early Thursday and again on Friday.

ILN WATCHES/WARNINGS/ADVISORIES
OH...None.
KY...None.
IN...None.

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