Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 202253 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 653 PM EDT Thu Jul 20 2017 .SYNOPSIS... A frontal boundary will slowly sag south across the region through the weekend. This will combine with a warm and humid airmass to produce occasional thunderstorms through the rest of the week and into the weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Remnants of a MCS were moving across the CWA early this afternoon. We have also seen separate scattered convective development across portions of eastern OH. MCS will likely continue to weaken and then dissipate as it moves across southern OH through mid afternoon. Expect a relative lull in convective activity after that due to some subsidence and lingering clouds behind this system. Most high resolution models then suggest that after this lull there will be renewed convection across the CWA sometime this evening, likely aided by sufficient instability (CAPE) and also an increase in shear particularly across the northern portion of the CWA. There is still uncertainty with the exact location/coverage of convection, and therefore have kept pops in the low chance category. Some of guidance also indicates convection making it pretty far south toward the Ohio River late at night. Can`t completely rule out this solution, but favored highest pops near/north of Interstate 70 where it looked more favorable for convection into the night. Any storms will be capable of producing locally strong/damaging wind gusts and also heavy rainfall that could lead to localized flash flooding. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... A hot and humid air mass will continue to reside over the CWA on Friday. There is general agreement that the morning will be dry. There may be some clouds to start to day, but with sufficient insolation maxima have the potential to be just as warm if not 1-2F higher than Thursday. Combining this with lower to mid 70s dewpoints brings heat index values into Heat Advisory criteria (100-104F) for a few hours Friday afternoon across portions of southeast IN, southern OH and northern Kentucky. As such, a Heat Advisory has been issued for these areas. Upper 90s heat index values are forecast further north. Uncertainty continues regarding convection Friday afternoon into Friday night. A cold front will likely sag down into central IN/OH which can serve as one focus for convection, but think that mesoscale influences may be more important and those details are not well known at this time. Followed continuity with chance of convection increasing in the afternoon/evening, and kept chance pops into the night especially across the northern CWA given the boundary in place and also potential for a new MCS to approach late at night. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Active weather pattern will continue into Saturday. Frontal boundary may move slightly northeast as a warm front, but its effective push will be dependent on where exactly another potential MCS moves. For now, an embedded disturbance in the northwest flow aloft to produce such an MCS is forecast to affect our northern zones where the highest PoPs have been placed. Chances for showers and thunderstorms then decrease as one heads toward the Tri-State. Potential for severe storms will be there due to adequate4 instability and deep layered shear. Heavy rain due to high pwats and potential flash flooding will also exist. Again, temperatures will be dependent on convection and convective debris clouds but should make the mid/upper 80s far north to the lower 90s south. Some heat indices may touch 100 briefly in the south on Saturday afternoon. For Saturday night, looks like another disturbance and perhaps a low level jet will generate another round of showers/storms with the northern zones again having the highest threat. On Sunday, models suggest that a weak boundary/trough axis may move east of the region by afternoon. As such, highest chances of showers/storms will be in our southeast with the lowest in the west. For Sunday night into Monday night, mid level trough axis will traverse the Great Lakes and Ohio Valley. This will be associated with a cold front that will move slowly southeast through the region. Will continue with a chance of showers/storms Sunday night, with decreasing chances of precipitation occurring as the front passes through. We should be dry for the most part by Monday night. Under northwest flow in the wake of the mid level trough, surface high pressure will build into the region Tuesday. The high will continue to extend and influence our weather into Wednesday. Dry weather and highs in the lower to mid 80s are expected. The next weather system may begin to affect the area by Thursday as return flow between departing high and an approaching cold front bring the next threat for showers and thunderstorms. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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VFR conditions are expected at least in the near term, with all TAF sites currently in an area with scattered clouds and no precipitation. As the next few hours progress, some showers and thunderstorms are expected to develop over Indiana. As this occurs, some of this activity may eventually move toward the TAF sites, but with a low probability of impact to any individual airport. Will continue to use a VCSH tonight to account for this. Later in the overnight hours, some MVFR visibilities and lower clouds (possibly MVFR/IFR ceilings) are likely to develop in northern Ohio. As some of this will likely drift southward into Columbus, some reduced aviation conditions are in the forecast near daybreak for KCMH/KLCK. There is a lower probability that IFR ceilings could form and move into the area, possibly affecting KDAY as well. Any chances for precipitation tomorrow appear marginal and disorganized, so they will not be included in the TAFs this far away. Aside from this possibility, VFR conditions are expected. OUTLOOK...Thunderstorms will be possible at times from Friday through Monday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...Heat Advisory from noon to 7 PM EDT Friday for OHZ077>082-088. KY...Heat Advisory from noon to 7 PM EDT Friday for KYZ089>100. IN...Heat Advisory from noon to 7 PM EDT Friday for INZ073>075-080. && $$ SYNOPSIS...BPP NEAR TERM...BPP SHORT TERM...BPP LONG TERM...Hickman AVIATION...Hatzos

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