Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 181936 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 336 PM EDT Fri May 18 2018 .SYNOPSIS...
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A broad area of low pressure will migrate northward into the area tonight through Saturday, providing scattered 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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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The first area of rain showers that moved through the northeastern two thirds of the ILN CWFA this morning and early this afternoon continues to migrate northwestward, allowing for a few breaks in the clouds near and south of the Ohio River. With this, low level destabilization is leading to re-initiation of scattered showers and isolated thunderstorms. This activity will increase in coverage through the afternoon hours as it progresses north-northwestward into the southern half or so of the FA. Although some low level instability is nudging into southern portions of the area (especially near and south of the Ohio River), expect that thunder chances will remain isolated to scattered at best, with very little chance for thunder closer to the I-70 corridor where extensive cloud cover continues to hold surface temperatures in check. Although brief breaks in the precipitation will work through the area, many locations will see on-and-off activity through the evening hours, with brief downpours possible in the heaviest activity. Not until late this evening will the activity make a more concerted push northward and eventually move out of the local area after midnight. This may leave most of the overnight period dry, but extensive cloud cover will linger, yielding yet another night of unseasonably warm temperatures as lows only fall to the low to mid 60s. Easterly winds will gradually go more southerly towards the end of the near term period as a weak surface low begins to track through western portions of the Ohio Valley. Although some patchy fog cannot be completely ruled out (especially for western parts of the local area), a fairly steady surface wind of around 10 MPH will likely preclude any widespread development, even with relatively moist low level conditions in place.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
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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.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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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.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
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A broad area of low pressure will slowly migrate northward through the Ohio and Tennessee Valleys through the TAF period, yielding periods of showers and scattered thunderstorms for about the entire region. More specifically, the first round of light rain from this morning continues to push off to the northwest with redevelopment of showers (and potential for scattered thunderstorms) now underway south/east of the local terminals. This activity will increase and overspread southern sites of KCVG, KLUK, and KILN through the heart of the afternoon and early evening hours before it begins to migrate northward after 00z. With any of the embedded heaviest areas of pcpn, tempo reductions in VSBYs (MVFR/IFR) or CIGs (MVFR) will be common. A relatively cohesive band(s) of rain is expected to push northward through the northern sites of KDAY, KCMH, and KLCK from approximately 00z- 06z before a brief minimum in pcpn coverage evolves from 06z- 12z area-wide. By 12z, however, with a weak surface low beginning to track through the western Ohio Valley, a shift to more southerly winds (and corresponding destabilization of the boundary layer) will be underway. In response, redevelopment of showers may very well be underway near or shortly after 12z from the south, which would potentially impact KCVG and KLUK first before activity increases in coverage and spreads northward through the afternoon hours. Although there may not be much pcpn in the area from 06-12z, MVFR/IFR CIGs will encroach upon western terminals of KCVG, KLUK, and KDAY as the surface low tracks through portions of Indiana. CIGs will likely improve to VFR area-wide towards the end of the TAF period. Winds will go more southerly towards 12z, with a shift to more southwesterly by the end of the TAF period. As with today`s activity, any pcpn during the day on Saturday will have the potential to lead to brief reductions in both VSBYs and CIGs, but confidence on timing and locations of such occurrences will be handled with additional updates. OUTLOOK...Chances for thunderstorms will exist at times through Tuesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...KC NEAR TERM...KC SHORT TERM...KC LONG TERM... AVIATION...KC

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