Sunrise 6:08 AM   Sunset 9:03 PM Moonrise 2:40 AM   Moonset 6:29 PM

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FXUS61 KILN 030130 AFDILN

AREA FORECAST DISCUSSION National Weather Service Wilmington OH 930 PM EDT Tue Jul 2 2024

SYNOPSIS
Hot and humid conditions are expected on Wednesday along with increasing chances for showers and thunderstorms as a cold front approaches from the northwest. This boundary will then remain in the area on the Fourth of July. Embedded mid level disturbances will interact with this boundary, resulting in multiple rounds of showers and thunderstorms. A stronger weather system is expected to move into the Great Lakes and Ohio region Friday into Friday night, continuing the threat for showers and thunderstorms.

NEAR TERM /UNTIL 6 AM THIS MORNING/
Ongoing fcst remains on track this evening as /mainly/ clear skies, aside from a few 4-5kft clouds from time-to-time, evolve through the near term period. Temps are running about 10-12 degrees above 24 hours ago and this pattern will maintain itself through the night as better LL moisture works its way into the local area. Expect conditions will remain dry locally through sunrise, with southerly winds increasing subtly toward daybreak.

PREVIOUS DISCUSSION...
Weather remains quiet across the area this afternoon with temperatures topping out in the upper 80s to lower 90s.

A weak, low-level trough is moving northward on the western periphery of the surface high pressure to the east, pumping better boundary layer moisture northward through central/northern Kentucky. Most dewpoints in the area are in the 50s, but mesonet stations across Kentucky are already indicating mid to upper 60s dewpoints entering the local area.
Light southerly flow will continue to usher in this better moisture over the next few hours before flow becomes more southeasterly this evening. This tongue of moisture will be directed northwestward, combining with the better surface moisture ahead of the approaching front. This moisture will be critical for humidity and thunderstorm development tomorrow afternoon.

Even with the better moisture entering the area this evening, no rainfall is expected with forcing remaining quite weak. After the afternoon cumulus dissipates, a few scattered upper level cloud linger into the early evening. Eventually, skies will clear with temperatures dropping into the upper 60s and lower 70s.

SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/
There is some potential for showers and thunderstorms to be ongoing early Wednesday morning across central Indiana. Whatever remnant activity moves into central Indiana will struggle to survive into the local area due to the corridor of lower dewpoint values across eastern Indiana and western Ohio. Even if the thunderstorms weaken, outflow boundaries and cloud debris will play a role in temperature and rainfall forecasts later in the day. At the same time, low level moisture will continue to improve (low 70s and perhaps mid 70s) as the convergence increases along the boundary. The increasing moisture and forcing along the front/other boundaries will ultimately lead to thunderstorm development during the afternoon and through the evening. All three of the below impacts remain noted in the HWO...

Heat: Confidence is fairly high that cloud debris will enter the area through mid-morning. Depending on how quickly this clears, some disruption to heating will be possible. Additionally, low- level moisture will be increasing during the day. Given this uncertainty, local heat conditions may rapidly change from the mid-morning hours into the early afternoon. Then, developing thunderstorms may quickly erode heat advisory conditions that have ultimately developed. The most likely area for a short- fused heat advisory would be across northern Kentucky, southwest Ohio, and southeast Indiana.

Severe: Day 2 Slight Risk (Level 2 of 5). With the heating and increasing boundary layer moisture, clusters of strong to severe storms are possible Wednesday afternoon and evening.
Damaging wind gusts are the main threat with some hail possible if an updraft split is able to change mean storm motion. At this time, downburst winds appear to be the more likely storm mode with limited ability for organization into bowing segments.

Heavy Rain/Flooding: While much of the area remains quite dry, stalled boundaries situated in a very moist atmosphere, in July, should always be viewed as potential heavy rain producers.
Ultimately, storm mode and boundary orientation remain the key factors. The latest 18Z HRRR shows how some back-building activity could provide isolated corridors of 2-3"+ into the evening hours. This would be beneficial rain for the abnormally dry conditions, but a few flood advisories may be possible in the heavier/more flood prone areas.

Thunderstorm coverage is expected to decrease a little during the overnight activity, but continue mid-level forcing and remnant instability will keep the threat lingering into Thursday morning.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
East-west oriented front will extend across the area at the beginning of the period. High precipitable water and deep warm cloud depths will extend along this same corridor. As a short wave moves across the area, showers and thunderstorms will occur with heavy rain potential and perhaps some damaging winds being the concern. Exactly where that boundary sets up, which latest data suggests will be near I-70, will have a greatest threat of heavy rain with the possibility of training and backbuilding.

As that impulse moves off to the east, there will be a relative lull in showers and any storms through late Thursday night.
During this time the boundary will lift north. More showers and storms will occur Friday, especially in the afternoon in part due to a pre- frontal trough pushing through the area. Airmass will be the same as on Thursday, so locally heavy rainfall will remain possible although convective elements will be progressive and less prone to training. Damaging wind threat will also persist.

The cold front will not move through until Friday evening with the chance of showers and thunderstorms lingering until that passes. High pressure will build in for the weekend and still be influencing the region into Monday. The next cold front will approach and move through the area Monday night into Tuesday bringing the next chance of showers and thunderstorms.

Warm, muggy airmass ahead of the first cold front will get replaced by something more seasonal for the weekend. But temperatures and dew points will be rising again early next week ahead of the next system.

AVIATION /02Z WEDNESDAY THROUGH SUNDAY/
VFR conditions are forecast through the TAF period, except within the SCT to numerous SHRA/TSRA that will develop after 18z Wednesday.

A thick band of cirrus will quickly push to the E of the local terminals within the first hour or so of the TAF period.
Thereafter, aside from a few VFR Cu from time to time, SKC will prevail until widespread diurnally-driven Cu develop/expand by/after 15z into the afternoon. SCT/BKN VFR Cu is expected by mid/late afternoon through the remainder of the TAF period, with thickening mid/high level clouds as well.

Light southerly winds at 10kts or less will be maintained through the overnight, with some SW LLWS at about 40-45kts possible at KCVG/KLUK between about 09z-12z. By 15z, sfc winds will have increased to 12-15kts, with gusts around 20kts, which will persist until SHRA/TSRA activity moves through and winds go more out of the WSW and subside a bit toward the evening after the storms. Expect the best coverage of TSRA activity to focus between about 20z-02z, with better coverage shifting to the S toward KCVG/KLUK toward/beyond the end of the TAF period.
The activity should be mostly TSRA, but maintained a VCSH for now given uncertainties in timing/location for any one site.

OUTLOOK...Thunderstorms possible Thursday through Friday.

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

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