Marine Weather and Tide Forecast for Alexandria, OH

KEY MESSAGES
1). Showers and thunderstorms are expected this afternoon and evening, with locally heavy rainfall and localized flooding and flash flooding being the main hazards. There is also a low end chance for an isolated severe storm this evening, with gusty winds being the main threat.

2). Additional rounds of showers and thunderstorms are expected Thursday and Friday. Locally heavy rainfall introduces a localized flood threat Thursday night. There is a low end severe weather threat Thursday evening ahead of a cold front moving through. The main threat will be damaging wind gusts.

3). Gusty winds are expected on Friday with a rapid drop in temperatures. Frost is likely this weekend.

DISCUSSION
Key Message 1)
An elongated slow moving cold front continues to sag southeast across the Ohio Valley region this evening into the overnight before stalling across the Kentucky Bluegrass region. This stalled boundary will provide the focus for multiple rounds of showers and thunderstorms near and south of the Ohio River this evening into the overnight.

Given MUCAPE values around 1000 to maybe 15000 J/kg and pockets of 0-500 bulk shear around 30 knots, a low threat remains in our southern counties for some stronger storms to produce isolated damaging winds, primarily during the early evening hours.

Tropical moisture continues to be advected across the region, allowing PWATS to reach 250 to 300% of normals for this time of year.
This, combined with skinny MUCAPE and a west to east storm motion, will allow for efficient rainfall rates and introduce a flooding/flash flooding threat for areas along and south of the Ohio River this evening. While most areas is this region will receive around 0.5 to 0.75 in of rain, cannot rule out some isolated pockets of 2-3 inches where storms move over repeatedly.

Key Message 2)

By Thursday, another developing wave of low pressure to our west will move east across the Central Plains and through our region. This feature will transition our stalled cold front/ stationary boundary across Kentucky into a warm front, and lift it back north across the region and pulling a new cold front toward the region from our west.
Showers and thunderstorms will develop ahead of this new front on Thursday evening.

The bulk of the rainfall Thursday evening into Friday looks to primarily impact east central IN and west central OH and areas north.
The tropical moisture remains in place and PWATs will continue to hang around 250-300% of normal. Most areas will receive a half an inch to 0.75 in, but CAMs paint some stripes of 1-2+ inches across portions of this region, introducing a flash flood threat Thursday evening/overnight.

Turning our attention to severe... While SBCAPE looks more limited (perhaps some splotchy 500-1000 J/kg near the Tri-State), a handful of CAMs paint MUCAPE between 1500-2000 J/kg, with the highest totals again near the Tri- State. Shear looks a bit more impressive on Thursday compared to Wednesday, with deep layer shear values between 30 to 50 knots, with the higher values across east central IN and west central OH.

Additionally, with a surface low moving right across Indiana, this does introduce quite a bit of directional shear to the forecast. The Supercell Parameter lights up across east central IN into the Tri- State from various CAMs and the Nadocast paints a 3% bullseye to our west (IL/IN border) but does scrape our eastern IN/ western OH counties with a 1-2%. While a tornado threat is quite low, we cannot rule a brief spin up.

With all that being said... tricky forecast indeed. Given that the weather will be arriving as we head into the evening hours, a low level inversion setting up will help pinch off SBCAPE. Additionally, the higher shear values will be slightly displaced from the more robust MUCAPE (based on today's guidance).

Key Message 3)
The low pressure system will move through the Ohio Valley off to the northeast and continue it's intensification, resulting in a strong cold front and cold air advection on the backside. This introduces a robust pressure gradient across the Ohio Valley region on Friday.
Northwesterly winds will be sustained around 15 MPH, occasionally gusting to 30 MPH. Winds will slowly taper off Friday night into Saturday.

The strong cold air advection regime will drop temperatures for the weekend substantially compared to what we've had this week. Friday night's lows fall to the upper 30s/low 40s while Saturday night we fall into the low/mid 30s area-wide, introducing the potential for frost across the region.

AVIATION /15Z WEDNESDAY THROUGH SUNDAY/
Showers and thunderstorms will move through the region this evening into the early overnight hours. Expect periods of heavy rain with reduced visibility at times. Widespread precip tapers off shortly after sunset and we'll be left with some isolated showers.

CIGs will drop during the overnight, especially for our southern sites (KCVG, KLUK, KILN), to MVFR and some patchy IFR. Areas north will likely fall to MVFR. Reduced CIGs remain in place through the remainder of the TAF period. Similarly, expect MVFR VSBYs across the same southern sites.

OUTLOOK...Thunderstorms are possible again on Thursday into Thursday night. Occasional MVFR conditions are possible through Friday.
Gusty winds out of the west northwest are expected on Friday.

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