Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 102044 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 344 PM EST Wed Jan 10 2018 .SYNOPSIS...
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Mild temperatures will continue tonight under a breezy southerly flow. A disturbance in the upper atmosphere coupled with increasing moisture will produce rain showers on Thursday. A strong low pressure system will bring accumulating wintry precipitation and colder temperatures Friday and Saturday.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Area is under a breezy southerly flow well ahead of low pressure centered along the Colorado-Kansas border. Atmosphere has dried enough to allow partial sunshine, which has combined with warm advection to cause temperatures to rise into the 50s and 60s. CVG has tied their record high of 61 for today, with DAY within one degree of their record of 58. Readings will fall back into the 40s for overnight lows. Expect dry weather for the most part in a regime lacking deep moisture and strong forcing. That said, a few showers may develop toward Thursday morning in increasing lift and moisture convergence ahead of the strengthening storm system.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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Models are in decent agreement in bringing a swath of showers by Thursday afternoon, when a jet streak and plume of moisture are forecast to arrive on an increasing southerly flow ahead of the low pressure system. Current indications are that the east half of the forecast area will receive the bulk of the showers, so went with categorical pops there. Locations to the west have chance to likely pops, possibly augmented late Thursday afternoon by energy and moisture arriving from the stronger system to the west. Well above normal temperatures will persist, with highs reaching the mid 50s to low 60s.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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Upper level energy over the lower Mississippi River Valley Thursday night will pivot northeast across the Tennessee River Valley on Friday, then to the New England region by Saturday. A perturbed surface low will track northeast along a slowly pushing cold front across the Ohio River Valley to bring a wintry mix of precipitation Friday into Friday night. The trends on the models have shown a weaker, faster, surface low rippling along the front. In turn, this is seen as weaker frontogenetic forcing to the left of the low track. For Friday, colder air will be filtering slowly south as a front pushes through. Colder air will under cut moist, warmer air aloft. This will allow precipitation to transition from rain to freezing rain/sleet, sleet/snow, and then eventually snow as we head into Friday afternoon and evening. The NAM is faster with the surface freezing line heading south than the GFS, so have taken a blended model approach for non diurnal temperatures. The NAM is slower to overturn the atmosphere aloft (warm bulge) than the GFS, which results in less snow and more ice/freezing rain. Have taken a 75 GFS/25 NAM for thermal profiles. All in all, snow amounts will be tempered, especially being dependent on how fast precipitation changes to all snow. In addition, the period of strongest frontogenetic forcing is more short lived, along with a small window of vertical motion intersecting the favored dendritic growth zone (- 12 C to -18 C), which will result in lower snowfall amounts. Given these reasons, did not feel confident enough to go with a Winter Storm Watch for a part of my area in the 4th and 5th period of the forecast. We will likely end up having at least an advisory everywhere, but questionable if we reach low warning criteria in parts of the area (4" in 12 hours versus 6` in 12 hours south versus north). So, latest thinking is about 3 to 5 inches for roughly the northwest two thirds of the CWFA (with near 4 inches being the mid point), with 2 to 4 inches the remainder of the southeast with 3 inches being the mid point. It should finally be noted that the pressure gradient will pick up Friday into Friday night with some gusts in the 25 to 30 knot range, which will cause some drifting and local blowing of snow. On Saturday, upper level energy and low will quickly pass on to the northeast. This will allow snow to taper off during the morning, followed by mostly cloudy skies in the afternoon. Temperatures will show little recover as CAA will continue. Highs will generally range from the lower to mid 20s. For Saturday night into Sunday, large scale mean mid level trough will once again set up shop across much of northern and northeastern parts of North America. This will bring a return to arctic air to the region. Surface high pressure is expected to traverse from west to east during this period. For Sunday night into Monday night, embedded shortwave energy in the northwest flow aloft will dig southeast into the Ohio Valley. This will be associated with another cold front. Still looks like a good chance of snow with this system as it passes through. Too early for snow accumulations, but there should be a least some. For Tuesday, cold air will remain in the wake of the system along with cold temperatures. Highs will be in the mid teens to the lower 20s with a lingering chance of snow across the north. By Wednesday, another ridge of high pressure will build into the region. It will remain cold. It looks like a warming trend is in the offing by the end of next week as mean mid level trough relaxes and a zonal to a southwest flow aloft begins to set up.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... TAF sites to be affected by increasing moisture and winds well ahead of a large and significant winter storm. Northern sites DAY ILN CMH and LCK will be closer to bulk of low level moisture, with MVFR ceilings forming by 24Z there, while CVG and LUK may see VFR persisting until around 04z. All sites can expect MVFR to last until about 16z Thursday when somewhat drier air is forecast to work in for a short time. Another element affecting aviation will be wind shear of 40 to 45 KT, developing first at southern stations CVG and LUK around 04z before spreading across the rest of sites by the end of the forecast. Rain showers will be possible in the vicinity of all sites near the end of the forecast period when an upper level disturbance is forecast to push through from the south. OUTLOOK...MVFR to IFR ceilings and visibilities likely Thursday night into Saturday. Snow and/or ice accumulations likely late Friday into Saturday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Coniglio NEAR TERM...Coniglio SHORT TERM...Coniglio LONG TERM...Hickman AVIATION...Coniglio

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