Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 082357 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 657 PM EST Fri Dec 8 2017 .SYNOPSIS... After high pressure settles to the southeast tonight, low pressure crossing Michigan will bring light snow accumulations on Saturday. High pressure is forecast to return Sunday with cold and dry conditions. A warm front developing ahead of the next area of low pressure will provide a chance of precipitation and milder temperatures on Monday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Surface high pressure stretching along the Ohio River should keep dry weather over the FA tonight. The high will settle to the southeast as low pressure develops over the Western Great Lakes, allowing increasing clouds from the northwest, and there is a low chance that snow may begin in far northwest counties near 6 am. While temperatures fall back into the mid and upper teens, wind chills down to the single digits will be noted. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... For Saturday morning, snow will develop over Northern Indiana in lift triggered by a mid level short wave and surface low rounding the base of a closed upper low positioned near Lake Michigan. The band of snow is expected to reach West Central Ohio and the Northern Miami Valley by around sunrise, where pops are categorical. Snow probabilities decrease to likely toward the Ohio River including Cincinnati where forcing and moisture will be less prevalent farther from the closed upper low and short wave. As the system progresses east, Central Ohio including Columbus should see a period of accumulating snow during Saturday afternoon, while the Southern Scioto Valley and Northeast Kentucky should see only a chance of accumulating snow. As the system continues to lift northeast Saturday evening, some enhancement of moisture from Lake Michigan may occur as the low level flow shifts to northwest and increases in the tightening pressure gradient of a trailing surface trough/cold front, producing snow showers into the overnight hours that could result in additional minor accumulations. Latest models show a shift away from Southeast Indiana and Cincinnati for the snow showers, and this trend is included in the grid forecast. Daytime temperatures in the upper 20s to lower 30s, falling to the upper teens Saturday night, will allow snow to accumulate readily. Storm total snowfall is expected to range from close to 1.5 inches across West Central Ohio, up to an inch in the 3 major metro areas, down to a half an inch or less in Northern Kentucky. These snowfall estimates, based on latest model guidance, are reduced a bit from previous attempts. Snow will diminish quickly toward Midnight behind the departing system, with precip probably ending by Sunday morning as a ridge of high pressure builds from the southwest. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The heart of a reinforcing shot of cold air will be shifting to our east on Sunday as a surface ridge traverses the region. Despite the beginning of some WAA, a cold start and still cold 850 mb temperatures will only allow for highs in the lower to mid 30s. Models suggest that a weak trof axis may clip our region Sunday night. Any possible light pcpn with this feature looks to stay to our north and northeast. For the period Monday into Monday night, models have converged on a similar solution with the track of a clipper system (area of low pressure) now expected to move across the Great Lakes. With the surface low tracking to our north, any isentropically driven pcpn should only clip our far northern zones on Monday, lifting to the north through the day as a warm front lifts north into our region. Temperatures will warm on a southwest flow with highs ranging from the mid 30s north to the mid 40s south. By Monday night, as the low moves east, a cold front will push southeast across the area. We should see a chance of snow showers with the boundary and in its wake as colder air filters back in our area. On Tuesday, post frontal stratocumulus clouds and cold air moving across the relatively warm waters of Lake Michigan will keep the threat for some snow showers. Highs will be early on with CAA allowing temperatures to slowly fall through the day. Axis of large scale mid level trough will pivot slowly east Tuesday night into Wednesday. Low level flow will begin to back away from the Great Lakes during this period, allowing for snow showers to taper off while a weak surface ridge builds into the Ohio Valley. The coldest air of the week will occur during this time frame. After lows in the 10 to 15 range, highs on Wednesday will struggle to warm into the 25 to 30 degree range. For the remainder of the extended, Wednesday night into Friday, a few weak weather systems will traverse the region in the northwest flow aloft. Timing, placement, and strength varies among the models, so only low PoPs will be used. Highs will be in the 30s with lows in the 20s. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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VFR conditions will prevail through 12z for all local terminals before snow arrives for the latter half of the period. A more- or-less continuous shield of -SN will progress from west to east across the area from approximately 14-22z, with the potential for isolated/scattered light snow showers and flurries lingering for several hours behind main band of light snow. There will be quite a bit of dry air in the lower levels to overcome at the onset of the -SN, which will likely inhibit, at least to some degree, very low CIGs or VSBYs even during the event. This being said, as the column gradually moistens, do expect MVFR CIGs to overspread all terminals during and immediately following the light snow. Brief MVFR VSBYs will also be possible in heaviest pockets of pcpn. Southwest winds will go more south-southwesterly after 12z then will become west-southwest as the cold front progresses through the area after 18z. Winds may become gusty (in excess of 20 kts) late in the period following the frontal passage before subsiding somewhat towards 06z Sunday. MVFR conditions will improve late in the period as well from west to east, with a return to VFR before the end of the KCVG 30-hr period. OUTLOOK...MVFR ceilings and visibilities are possible Monday into Tuesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Coniglio NEAR TERM...Coniglio SHORT TERM...Coniglio LONG TERM...Hickman AVIATION...KC

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