Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 190047 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 847 PM EDT Fri May 18 2018 .SYNOPSIS... A broad area of low pressure will migrate northward into the area tonight through Saturday, providing widespread showers and thunderstorms. Another system will move into the region Sunday into Monday, keeping precipitation chances in the forecast through early next week and a continued warm and humid airmass. Drier weather may return by midweek next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Went ahead and issued a short flash flood watch for portions of the tristate area given additional heavy rain moving into the region. Updated the forecast to add heavy rain mention in across southwestern portions of the forecast area across the tri-state especially. Over 4 inches of rain has already occurred in some locations. Thunder will be primarily limited to the south this evening where there is the better instability. Rain showers will overspread the rest of the region and remain in place this evening and into tonight. Rain activity will gradually decrease in coverage late in the overnight hours. Updated the HWO to include flood threats across primarily the western half of the forecast area for this evening and into the overnight hours. Only minor changes to the rest of the forecast at this time.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... A weakly-defined surface low will be tracking west and northwest of the local area at the beginning of the short term period, with the front expected to be oriented approximately west to east just north of the FA. Although cloud cover will be a bit thicker and more widespread for western parts of the area, breaks in clouds in the eastern half or so of the region will allow for spotty shower and thunderstorm development fairly quickly/early during the day on Saturday. With diurnal heating, activity will increase in coverage as it moves northeast from the late morning through early evening hours. Even though the individual weather features involved in tomorrows environment are relatively weak and ill-defined on their own, any surface low moving through the Ohio Valley in mid-May certainly deserves a second look from a severe risk perspective. Do think that the MRGL risk per SPC in the east is well justified as low level destabilization will be more robust and widespread than is being experienced today (Friday). With this being said, the wind fields aloft are fairly weak and will likely limit organization of storms to a degree. With sufficient instability and lack of any notable shear and/or focused forcing mechanism aloft, the environment and evolution will bear watching, but the overall threat will likely remain closer to the low end of the scale. Certainly cannot rule out some small hail or gusty winds in the strongest cells that develop Saturday. Highs will top out in the mid 70s to around 80 degrees on Saturday. By Saturday evening, the surface low will be pulling away from the local area and with the loss of daytime heating, expect a fairly rapid downtick in convective coverage towards sunset. Nevertheless, as the surface low pulls away, the trailing cold front will once again begin to stall over the local area Saturday night into Sunday, with lows ranging from the upper 50s in the north to the mid 60s in the south. With the frontal boundary continuing to linger in the area, the threat for daily scattered showers and storms will continue Sunday into the first part of the long term period. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Wavy quasi-stationary front will extend across the region at the beginning of the period. The front may briefly lift north of the area as low pressure tracks across the lower Great Lakes on Tuesday. But as the low heads east, a trailing front will slide across the area. Unsettled conditions will persist through this time period with sporadic showers and thunderstorms. Center of high pressure will track from the Great Lakes to off the New England coast from Wednesday through Friday. The influence of this high will bring dry conditions to the forecast area for the latter part of the week. Temperatures will be above normal through the period with lows having a greater departure from normal than highs. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... Showers will move across the TAF sites at the start of the TAF period and into the overnight hours. There will be thunderstorms also around the KCVG and KLUK TAFs at the start of the TAF period. Vsbys will be reduced with some of the precipitation activity. Cigs will lower overnight into the IFR and MVFR categories and then rise to MVFR during the day on Saturday. Additional showers and thunderstorms will be possible on Saturday in addition to some wind gusts around 20 knots. OUTLOOK...Chances for thunderstorms will exist at times through Tuesday. && .ILN WATCHES/WARNINGS/ADVISORIES...
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OH...Flash Flood Watch until 1 AM EDT Saturday for OHZ077-078. KY...Flash Flood Watch until 1 AM EDT Saturday for KYZ090>098. IN...Flash Flood Watch until 1 AM EDT Saturday for INZ074-075-080.
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