Sunrise 6:34 AM   Sunset 8:36 PM Moonrise 3:41 AM   Moonset 3:44 PM

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FXUS61 KILN 041723 AFDILN

AREA FORECAST DISCUSSION National Weather Service Wilmington OH 123 PM EDT Sat May 4 2024

SYNOPSIS
A warm and moist airmass will remain in place across the region into the middle part of next week, leading to occasional periods of showers and thunderstorms.

NEAR TERM /UNTIL 7 PM THIS EVENING/
Fcst was updated a bit to increase PoPs this morning into this afternoon as there is already quite a bit of SHRA/TSRA activity in various pockets throughout the ILN FA. Although the severe threat remains very low, very heavy downpours and frequent lightning is occurring with some of this activity. Isolated heavy rain/ponding of water has already occurred, with some stations from Owen to Boone Cos KY picking up more than an inch of rain in ~30 minutes. Brief ponding of water can be expected with these rates, with isolated flooding due to 1.5 to 2 inches possible in the more persistent bands.

PREVIOUS DISCUSSION...
Mid level short wave energy will lift northeast across the mid Ohio Valley through the day. Forcing isn't terribly great, but in a moist airmass, this has been enough to maintain scattered shower activity across southeast portions of our area so far this morning. Flow aloft is very light, so this activity will very slowly pivot up across mainly eastern portions of our area through mid morning.

As we head through late morning and into this afternoon, some weak instability will develop as afternoon highs push into the mid to possibly upper 70s. This will allow for a continuation of occasional showers along with a chance for thunderstorms. Given the light flow and general lack of deeper shear, the overall severe threat will be low. However, with PWs up around 1.5 inches and the slow storm movement, some heavier downpours will be possible today.

SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SUNDAY/
As we lose the daytime heating and the mid level short wave moves off to our northeast, expect an overall decreasing trend in pcpn this evening and into the overnight hours. Lows tonight will mostly be in the lower 60s.

Another mid level short wave will move east across the Great Lakes region on Sunday. An associated weak surface wave will move across the southern Great Lakes while a trailing weak cold front moves east across our area during the day on Sunday. This will lead to additional chances for showers and thunderstorms, especially across eastern portions of our fa Sunday afternoon.
With a little better deep layer shear, a few strong to severe storms may be possible across our eastern areas Sunday afternoon. The main severe threat would be damaging winds.
Highs on Sunday will range from the mid 70s northwest to around 80 degrees in our southeast.

LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/
A strong surface high over MI will push drier air into the northern Ohio Valley behind a departing cold front. A s/w undercutting a mean H5 ridge will move east and into the Ohio Valley on Monday. The earlier cold front will have draped w-e through southern CWA Monday, and then begin to lift northeastward as a warm front overnight. The region will be warm-sectored on Tuesday with scattered showers and thunderstorms expected with daytime heating. Earlier showers with embedded thunderstorms on Monday/overnight look to be triggered by the surface front.

Tuesday night, warm sector showers will scatter out as a convective line works in from the west ahead of a H5 s/w and trailing the exiting upper ridge. This looks to be behaving as a cold front, but the only front mildly shown in guidance is a shift from the highest moisture on Tuesday to slightly drier air (back to what has been seen) overnight.

A brief drying on Wednesday will change after daytime as strong southwest flow brings a continued feed of deep moisture that will be wrung out overnight. This will be the most prominent rainfall period in the extended forecast. While some showers may linger into Thursday/Thursday evening ahead of a H5 trough, the region should be fairly worked-over enough to where upper level lift will not overcome an expected stable airmass behind Wed night's rain.

Low chance pops continue through the forecast but the overall end of the period beginning Thursday evening looks to be dry and cooler.
Cooler to the extent that from Thursday night through Saturday it will be near seasonal normals. Beginning with a brief cooling on Monday, temperatures will warm through Wednesday and cool through the remainder of the period.

AVIATION /18Z SATURDAY THROUGH WEDNESDAY/
Following the AM SHRA/TSRA activity, additional (albeit very disorganized) redevelopment is underway, especially NE of KCVG/KLUK. This cellular activity will continue to slowly drift to the NNE, remaining incredibly disorganized and "popcorn- like," perhaps transitioning to one or more clusters as we progress late into the afternoon/evening. Nevertheless, attempting to time out impacts at any one site is incredibly challenging given the nature of the activity. So, decided to broad-brush a VC for KDAY/KILN/KCMH/KLCK, with a TEMPO for time windows of greatest expected coverage. Sudden reductions in VSBYs will be the primary concern with any of the activity.
Certainly a brief SHRA/TSRA could once again meander near/over KCVG/KLUK after about 21z, but confidence in this occurring was too low to include in the fcst at this juncture.

A mix of VFR/MVFR/IFR CIGs continue to linger about, with a gradual transition to mainly VFR/MVFR through the first hour or so of the TAF period. Numerous SHRA/TSRA will slowly wane in coverage from W to E past 00z, with drier conditions evolving locally toward/beyond 03z. CIGs may trend back to, or below, 2000ft past 06z or so, but there are uncertainties in just how widespread the MVFR (or even IFR) CIGs may be after 06z through mid morning Sunday. There also could be some VSBY reductions develop tonight due to BR/FG as well, particularly at KCVG/KLUK where more widespread rain occurred this morning. A stray SHRA cannot be ruled out at KCVG/KLUK/KDAY between about 07z-09z as a decaying patch of pcpn moves in from the W.

A front will move into/through the local area on Sunday, allowing for winds to go more westerly late in the period. Until then, light SW winds at 7-9kts or less are expected.

OUTLOOK...Thunderstorms are possible at times each day from through Wednesday. MVFR or IFR conditions are possible Monday morning.

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

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