Area Forecast Discussion
Issued by NWS Wilmington, OH

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036 FXUS61 KILN 111802 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 102 PM EST Mon Dec 11 2017 .SYNOPSIS... An area of low pressure and associated cold front will move across the region this evening into tonight. A second disturbance will work through the area on Tuesday. Another low pressure system will work through the region Wednesday night into Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Southerly flow in advance of the next system will allow for warmer temperatures today with highs in the middle 30s to the middle 40s. The approaching system will allow for an increase in mid and high clouds today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... An area of low pressure will track along the northern edge of the forecast area this evening into tonight. A trailing cold front will bring some cooler air to the area along with some light precipitation chances. There is some upper support with this feature as well. After this initial feature moves by there will be a few hour period late in the overnight hours early Tuesday morning where model soundings indicate more of a drizzle sounding with no ice in the cloud. Temperatures are around freezing and below freezing in some cases during this time. As such, have a chance for drizzle and freezing drizzle in the forecast for this time across a large portion of the forecast area. In addition, after this initial feature winds will begin to pick up as well. By around daybreak a second upper level disturbance and reinforcing shot of cold air pushes into the area. Winds become quite gusty with wind gusts around 30 to 40 mph. These wind gusts are expected to remain in place through the day on Tuesday. Temperatures will fall some through the day. The combination of the cold temperatures and the winds will allow for wind chill values in the single digits across most of the area. With the second feature sounding profiles will be cold enough as precipitation will change over to all snow. In addition to scattered snow showers and potentially some snow squalls, an enhanced lake band also looks to develop. This band of snow will be where the most accumulating snow will be located. Across far northwestern portions of the forecast area closer to the lake, a thin area of potentially 2 to 4 inches of snow will be possible. Further away from the lake values will generally be a half inch to upwards of 2 inches in the band. Southwestern portions of the forecast area are likely to see the least amount of snow of a half inch or less since the better lake trajectories for longer amounts of time stay further northeast of their location. With the gusty winds during this time expect visbilities to be reduced with snow showers and the band of snow that does develop. Please use caution late Monday night through the day on Tuesday with potential impacts from falling temperatures/wind chill values, freezing drizzle concerns, gusty winds, snowfall, and subsequently reduced visibilities from snow. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Lake effect band will be weakening in the evening before dissipating as winds back. Ridging will briefly cross the area late Tuesday night into Wednesday morning. But the next system will already be approaching the area by Wednesday afternoon. 00Z models still showing some differences in timing/location of low pressure that will pass through the region Wednesday night into Thursday. Have leaned towards the GFS ensemble mean which is a reasonable compromise between the operational GFS and ECMWF. There will be snow ahead of and north of the low track. Given uncertainties, have still limited PoPs to the chance category. Expect this activity to quickly move off Thursday morning. There could be an inch or so accumulation somewhere in the northern part of the forecast area. Behind this system, there will be further reenforcement of cold air, but it will be short-lived. The upper pattern will be deamplifying and robust southwest low level flow will allow temperatures to warm above normal for the weekend. There is timing uncertainty with the passage of a cold front that may occur late in the period. An influx of moisture ahead of this will bring the next chance of showers, mostly rain showers, although there could be some snow if it starts early enough, with the better chance of precipitation in southeast areas. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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Low pressure near the Mississippi River Valley will deepen as it tracks east across the southern Great Lakes tonight. As the low goes by, a cold front will swing southeast through our region. Models in the low levels are very dry ahead of the low and south of the warm front, so despite some dynamic lift with associated vigorous disturbance aloft, it should remain dry ahead of frontal passage. Behind the front, decent CAA will filter into the region. CAA across the relatively warmer waters of the Great Lakes will help induce scattered snow showers as instability increases. In fact, high resolution models continue to indicate the potential of a long lake effect snow band, or "streamer" setting up across our western CWFA on Tuesday. In addition, synoptic scale winds will increase due to tightening pressure gradient and mixing of higher winds aloft. So, for this TAF package, have VFR conditions becoming MVFR behind the front. Snow showers were placed at KDAY/KILN where the highest threat will be by the "streamer." Have used 3SM for now, but this will have to be fined tuned when confidence increases. Aviators should be away that the lake effect band or "streamer" will have the potential to drop visbilities to less than a half mile along with locally blowing snow. Winds will be from the west and northwest sustained between 15 and 20 knots with gusts in the lower 30 knots. By Tuesday evening, scattered snow showers/flurries should decrease once the sun sets, with the lake effect band rotating to the north and weakening as winds in the low levels back with time away from Lake Michigan. Surface winds will begin to decrease in speed as well. OUTLOOK...MVFR ceilings and visibilities possible Wednesday night. Gusty winds are expected Tuesday into Tuesday evening.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Novak NEAR TERM...Hickman/Novak SHORT TERM...Novak LONG TERM... AVIATION...Hickman

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