Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 232346 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 646 PM EST Tue Jan 23 2018 .SYNOPSIS... Low pressure over the Great Lakes will continue to move northeast of the region, but cold air behind the system will keep cloudy skies and a chance of light snow in the forecast through tomorrow. Dry conditions will return as high pressure moves into the southeastern states on Thursday, and temperatures will gradually warm up going into the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... Current observations show that surface low pressure is centered about 200 miles NNE of Toronto ON, well occluded from a frontal boundary that is now nearing the Atlantic coast. Consistent WSW flow through the boundary layer has continued to cold advect through the day, leading to a well mixed temperature profile through the lowest 3000-4000 feet. Precipitation types have generally switched to rain this afternoon, with surface dewpoints remaining above 32F in most locations, but this should begin to change over the next hour or two. There is evidence in recent HRRR data and satellite imagery of another shortwave at the far southwestern periphery of the main mid-level trough, currently moving across Indiana and sparking some cellular shower development. Soundings indicate very, very small amounts of instability below 5kft, which supports some slight increases to PoPs tonight as this activity moves into the ILN CWA. Outside of this particular area of precipitation, a mix of light rain and snow (maybe better described as sprinkles and flurries) will eventually switch to snow as temperatures continue to fall. Not expecting any snow accumulations, beyond maybe a very slight chance of a tenth or two if the cellular activity turns to snow later in the evening. Chances for flurries were carried through the overnight hours, with 850mb/925mb moisture remaining in place. && .SHORT TERM /WEDNESDAY NIGHT/... The coldest 850mb/700mb temperatures expected this week will move through the middle Ohio Valley on Wednesday afternoon. This will set up Wednesday as the coolest day of the week (lower to middle 30s), and also another very cloudy day, with RH near/at saturation at the top of the mixed layer through the afternoon. This RH should begin to break up by evening as temperatures aloft begin to warm. Flurries were added to Wednesday as well, with some weak ascent also expected in advance of yet another shortwave moving through the area. If this shortwave continues to trend toward being better defined and slightly stronger, as it did in the 12Z model cycle, some PoPs and light accumulations may need to be added in later forecasts. On Wednesday night, heights will begin to rise quickly, as surface high pressure makes its closest approach to the region (though it will be centered well to the south). As is usually the case, this position in the overall pattern supports the coolest min temps for the period, with light surface winds and skies beginning to clear. Forecast min temps have been lowered by several degrees -- now ranging from the lower to middle 20s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Mid level ridging will push east across the region Thursday into Friday. An associated surface high pressure will be centered across our area Thursday morning before beginning to shift off to the east through the day. This will help keep us dry on Thursday with temperatures a few degrees above normal. Dry conditions are also expected Thursday night into Friday. As we start to get on the back side of the high, southwesterly low level flow/WAA will be on the increase. This should help push highs on Friday into the low to mid 50s. Mid level short wave energy will drop down out of the upper Midwest on Saturday and across the upper Ohio Valley through Sunday, helping to push an associated cold front east across the region Sunday morning. Ahead of this, there will be an increasing chance of rain showers Friday night with pcpn then becoming more widespread Saturday into Saturday evening. There is some uncertainty with possible energy riding up along the front Sunday and just how long any pcpn will linger across our area. For now, will go ahead and trim pops back to chance category through the second half of the weekend. Ptype will be all rain initially, but as CAA develops on the back side of the front, there will be a mix with and then possible transition over to snow through the day on Sunday. Highs on Saturday will be in the low to mid 50s, with some non diurnal temperatures then possible through Sunday as the front moves through. A few snow showers may linger into Monday depending on just how fast the upper level trough takes to pull out of the area. Ridging and drier conditions will then work back into the region through mid week. Temperatures will remain near seasonal readings through the later part of the long term period. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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Scattered rain and/or snow showers will diminish from west to east through 06Z as a surface trof and its associated upper level disturbance move east out of the region. Locally gusty winds will diminish as well. CAA will continue with widespread stratocumulus deck providing for MVFR ceilings generally between 1400 and 1800 feet. On Wednesday, another upper level disturbance is forecast to move east across the region during the afternoon and evening. Some weak low level forcing associated with this feature may produce a few snow flurries or isolated snow showers. Otherwise, stratocumulus deck will persist through the day with heights likely rising to around 2500 feet by 18Z. For Wednesday night, as the disturbance moves away, surface ridging will build east into the Ohio and Tennessee Valleys. Stratocumulus deck should lift to VFR and gradually move east out of the region overnight. OUTLOOK...MVFR ceilings and visibilities possible Saturday into Sunday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Hatzos SHORT TERM...Hatzos LONG TERM...JGL AVIATION...Hickman

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