Area Forecast Discussion
Issued by NWS Wilmington, OH

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983 FXUS61 KILN 170015 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 815 PM EDT Fri Mar 16 2018 .SYNOPSIS... High pressure will move east of the area tonight, as an area of low pressure moves east from Missouri through Kentucky. This will spread a mix of rain, freezing rain, sleet, and snow into the northern Ohio Valley. High pressure will move back into the area on Sunday and Monday, before another area of low pressure brings precipitation to the region on Monday night and Tuesday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Did not make any sweeping changes as the advisory in effect for later tonight was dependent on earlier forecast. Minor changes such as bumping temps up slightly and delaying the onset of rain by a tiny bit should not necessitate any changes to the overall forecast and validity of winter weather advisory. Also bumped up sky cover significantly early on, hence the slight rise in temps tonight. With a warm advection pattern tonight, min temps will be reached early in the 3-6Z time frame. Temperatures will get into the upper 20s in central Ohio, but will remain in the lower to upper 30s across the southeast sections of the forecast area.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... By Saturday morning, the area of surface low pressure will be moving eastward across Missouri and into southern Illinois. A frontal boundary extending ESE from this low is currently located well south of the ILN CWA, but it will begin to move to the north as it strengthens, with a tightening theta-e gradient developing along an axis from northeast Missouri to eastern Kentucky. At and above 925mb, there will be a significant push of warm/moist air into the ILN CWA, especially between 03Z-12Z. With the 925mb/850mb low centers a little further north than the surface low center, these levels will warm up more quickly than at the surface, where winds should remain cool and easterly into the morning. As a result of increasing 850mb convergence, and ahead of a mid-level wave on the northeastern periphery of the surface low, precipitation will become widespread moving into the ILN CWA during this time frame. Early in the event, the dominant precipitation type is expected to be freezing rain, especially along and north of a line from Franklin County IN to Scioto County OH. For these locations and areas to the north, a winter weather advisory is in effect -- expanded slightly from the previous issuance. The heaviest forecast precipitation amounts, and the greatest confidence for up to a tenth of an inch of ice, will be on a swath of real estate extending roughly from Greenville OH to Chillicothe OH, extending about a county or so to the north and south on either side of that line. The southern end of the advisory is definitely very marginal, with surface temperatures that will be very close to freezing, and relatively warm antecedent conditions (sunny conditions on Friday afternoon with temperatures near 40). Also, there is a cooling aloft that noses into the northern sections of the forecast area at around 12Z, which may lead to a p-type switch to snow/sleet in the northern couple tiers of ILN counties for a couple hours. Ultimately, precipitation is expected to get much more showery and scattered after 15Z, though precipitation types will generally be changing to rain after that point anyway. After the compact 500mb trough passes by in the early evening, the threat for precipitation should end, with subsidence and surface high pressure enveloping the area through the overnight hours. Behind the bulk of the precipitation, temperatures on Saturday will warm into the lower to middle 40s, though a very sharp gradient in temperatures will exist just south of the ILN CWA (where the surface front will be stalling out. Min temps Saturday night will drop into the middle to upper 20s, with clearing expected, especially in the northern half of the forecast area. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The region will be under the influence of a surface high pressure at the onset of the extended period. Skies will be mostly sunny, allowing temperatures to rise to around 50 in the north and the mid 50s in nrn KY. Another in a series of H5 s/w will kick out of the Rockies on Monday. Models have remained consistent in shearing the s/w and weak sfc low through the plains and into the TN Valley. This keeps the pcpn south of the region for Monday. Highs will once again range from around 50 in the north and the mid 50s in nrn KY. The system then pushes into the region Monday night, spreading rain up across the region. Some snow might mix in over the northern counties where cooler air will try to interact. Models are still showing agreement as they dig secondary energy into the system on Tuesday, producing a deep trof over the ern U.S. This allows a broad sfc low to linger in the central to southern Appalachians, which keeps pcpn across the fa. Temperatures warm enough on Tuesday to change pcpn to rain, but as the sfc low begins to work to the east, colder air spill in on the backside. Critical thicknesses drop Tuesday night changing the pcpn to snow. Another cycle of changeover to rain is expected Wednesday and back to snow Wednesday night. High pressure returns for Thursday, but temperatures will be well below normal. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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Until the better rain showers enter later tonight, VFR conditions will prevail. Cigs will lower as the rain begins after midnight, but the initial onset of rain will occur from a higher VFR cloud deck. After a few hours of moistening the column, MVFR cigs will occur before daybreak in most locations. Rain will prevail at CVG/LCK tonight and Saturday. An early shot of freezing rain mixed with plain rain will occur at KDAY and KILN, changing over to rain as daytime insolation begins after sunrise. CMH/LCK will be the last to see what will be a wintery mix in their area begin. It would likely take another 2-3 hours after daybreak to warm this area to where any continued precipitation in the morning would change to primarily rain. After the prevailing rain ends in the late morning/early afternoon, there could still be some lingering showers underneath an MVFR cig just about anywhere, but more likely to the south at CVG/LUK/ILN airports. Rapidly improving conditions will be found tomorrow evening. Easterly winds will prevail through the forecast as the low pressure system tracks east through Kentucky from late morning to early evening. OUTLOOK...MVFR ceilings and visibilities are possible from Monday night through Tuesday night.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...Winter Weather Advisory from midnight tonight to noon EDT Saturday for OHZ026-034-035-042>046-051>056-060>065- 070>074-077>082-088. KY...None. IN...Winter Weather Advisory from midnight tonight to noon EDT Saturday for INZ050-058-059-066. && $$ SYNOPSIS...Hatzos NEAR TERM...Franks/Hatzos SHORT TERM...Hatzos LONG TERM...Sites AVIATION...Franks is the U.S. government's official web portal to all federal, state and local government web resources and services.