Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 282342 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 742 PM EDT SAT MAY 28 2016 .SYNOPSIS... The Ohio Valley region remains in between low pressure in the upper Mississippi Valley and high pressure off the mid-Atlantic coast. This will support a chance of showers and thunderstorms at times through Sunday. After a cold front moves through on Sunday evening, drier conditions are expected for Monday and Tuesday, with surface high pressure moving into the area. Chances for precipitation will increase again later in the week. && .NEAR TERM /THROUGH SUNDAY/... Both at the surface and aloft, low pressure is located over the upper Mississippi Valley, and high pressure is centered just east of the mid-Atlantic coast. With little-to-no impact from TD2 expected with regards to the overall pattern over the Ohio Valley, nothing significant has changed for the ILN forecast area, in a regime of weak forcing and very slightly confluent flow in the boundary layer. With no significant capping today, showers and thunderstorms have been able to develop, though the weak forcing and near-zero wind shear have kept this activity very disorganized. Signals from various high-res models (HRRR / NSSL-WRF / WRF-NMM) are all very similar, focusing the period of scattered thunderstorms through the peak of the diurnal cycle -- and allowing for much drier conditions by evening. Without any other clear signals for storm focus in either model or observational data sets, the current forecast (30-50 percent chance of storms) will remain in place through evening, before switching to dry conditions overnight. The air mass has changed only slightly from yesterday (outside of the storms), but is generally a little more moist. Based on current dewpoints, and looking at last night`s low temperatures, a min temp forecast in the middle to upper 60s appears reasonable. && .SHORT TERM /SUNDAY NIGHT/... Sunday is expected to begin with generally dry conditions, with very little overall adjustment to the weather pattern. That will change later in the day, as the troughing over the upper midwest moves northeast, and begins to flatten the east coast ridging into more of a zonal pattern across the Ohio Valley by Monday. As this process occurs, and as the axis of the trough (weak as it may be this far south) moves through, a weak cold front will also move ESE across MI/IN/OH. Neither the air mass change or wind shift with this front will be particularly strong, so the amount of forcing it will provide is definitely worth questioning. Otherwise, ahead of the front, the pattern will remain weakly forced -- probably similar to today (Saturday), with a chance for disorganized storms (generally on the weaker end of the scale) to develop as diurnal heating kicks in. Any chances for stronger storms will probably be limited to areas closer to the front, which based on timing would probably only really include the northwestern section of the ILN forecast area. Shear is not going to improve from current conditions -- 0-6km values of around 20 knots, and much less closer to the ground. Though instability will not be lacking (MLCAPE forecast to be 1200-1800 J/kg on Sunday afternoon), the forcing and shear are too weak to support a significant severe threat, with too low of confidence to even mention in the HWO at this point in the forecast process. Max temps for Sunday were increased slightly ahead of the front, especially in the southeastern CWA, where temperatures today are pushing well into the mid 80s. Expected clouds and possible convection will keep temperatures a little lower in the northwest. The slightly drier air moving in behind the front on Sunday night will allow for min temps in the lower 60s. && .LONG TERM /MONDAY THROUGH SATURDAY/... In the wake of a weak cold front, high pressure will settle across the region for the Monday/Tuesday time frame. Above normal readings will continue with highs in the lower to mid 80s and lows in the lower 60s. A mid level trough will be the main weather feature from mid to late week as it slowly progresses from the northern/central Plains to the Great Lakes. We should squeeze out one more dry day Wednesday, with increasing chances for showers/storms late Wednesday night into Thursday as associated surface cold front moves into the region from the west. By Friday, the front will slip south of the Ohio River, with drier conditions moving in behind. Temperatures will cool some due to clouds/precipitation and then eventually some CAA in the wake of the front. For the upcoming weekend, models continue to forecast a long wave trough developing over the western Great Lakes and extending southward into the mid/lower Mississippi River Valley. There are some indications that a weak impulse rotating through the eastern part of this trough axis may bring a chance of showers and storms across our eastern/southern zones on Saturday where mid to upper level lift and deeper moisture will exist. The lower heights and cooler 850 mb temperatures will result in temperatures going below normal, with highs in the lower to mid 70s and lows in the 55 to 60 degree range. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/...
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Scattered convection continues to pop up late this afternoon. Based on radar coverage attm included a tempo of MVFR TSRA at KCMH and KLCK for the first hour of the TAF period. It is looking like the rest of the TAF sites will remain dry this evening as pcpn is expect to disipate with the loss of daytime heating. Clouds from the convection to the west should provide a cirrus canopy overnight. By 09Z, models are bringing an increase on H8 moisture as upper level vorticity works into the region on the SW flow aloft. Brought a VFR cig into the wrn TAFS with this feature and gradually spread it over the ern TAFS by 12Z. By 12Z, upper level energy and some moisture from TS Bonnie reaches the ern portions of the fa. There could be some scattered showers during the morning due to this feature. The clouds cover and showers should help deter convective development for a good part of the day, but by 21Z a consensus of the models bring a line of thunderstorms into the wrn TAFS. Covered this with VCTS since it is towards the end of the TAF period. OUTLOOK...Showers and thunderstorms are possible Thursday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Hatzos SHORT TERM...Hatzos LONG TERM...Hickman AVIATION...Sites

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