Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 211731 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 1231 PM EST Tue Nov 21 2017 .SYNOPSIS... As high pressure moves off the east coast, a cold front will move into the Ohio Valley today, bringing some scattered showers to the area. Cold air will move in behind the front as high pressure builds into the region for Wednesday and Thursday. Temperatures will warm slightly for Friday, before another cold front approaches the region early in the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Surface high pressure is moving off the east coast, as an area of surface low pressure north of Lake Superior gradually moves ENE to northern Quebec. A cold front extends southwest from this low, and is forecast to cross the Great Lakes and Ohio Valley through this afternoon and evening. With the cold front currently over Lake Michigan, radar shows virga as precip aloft fights dry air in low levels. The atmosphere will slowly moisten as the front approaches, and showers should begin to reach the ground soon around Northern Illinois and Indiana. Expect a few showers to reach our far northwest counties by 6 pm. Winds will also be an issue today, with gusts in the 20-30 knot range expected, primarily in the northern half of the forecast area. With frontal timing primarily expected to be an evening issue, temperatures through the period should be roughly diurnal, with afternoon temps rising to the lower 50s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... The cold front will be moving through early tonight. A band of scattered to numerous rain showers is expected to sweep across northern counties this evening along and just behind the front. A few snow flakes may mix in as cold air filters in on a northwest flow. A relatively simple weather scenario is expected for Wednesday, as surface high pressure begins to nudge into the area from the middle Mississippi Valley region. Deep- layer NW flow will keep a cold advection pattern in place, resulting in conditions that will be notably cooler (highs in the upper 30s to lower 40s) and somewhat drier (dewpoints in the mid 20s) than on Tuesday. One concern is in how quickly the post-frontal stratocumulus clouds will clear out behind the front, and expectations are that these clouds will likely not dissipate immediately -- persisting, at least in part, through Wednesday morning. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Surface high pressure will settle across the Ohio Valley Wednesday night. It will initially start out mostly clear, but a weakening disturbance in the northwest flow aloft will spread some mid and high level clouds into the region overnight. Temperatures should bottom out in the lower to mid 20s. Thanksgiving Day will be dry as high pressure continues to influence the region. Under a mix of clouds and sunshine, it will be chilly with highs in the lower to mid 40s. For Thursday night into Friday, a mid level trough will dig southeast from the western provinces of Canada into south central Canada/northern Plains. As this occurs, a cold front will push southeast. WAA ahead of the front will boost temperatures into the upper 40s and lower 50s on Friday. For Friday night into Saturday, mid level trough will dig east into the Great Lakes and the Ohio Valley. Aforementioned cold front will move east through our region Friday night into Saturday morning. Moisture is limited, and some models, such as the ECMWF, move the front through dry. Thus, will keep PoPs in the slight chance/low chance range north of the Ohio River. Skies are expected to be partly cloudy behind the front on Saturday. Given a warm start, sunshine, and relatively weak CAA, we should see highs similar to Fridays readings (upper 40s to the lower 50s). For Saturday night into Sunday, secondary energy will dig into the western side of the mid level trough, strengthening it over eastern Canada, the eastern Great Lakes, and New England. This will push a secondary cold front through the region. It appears that CAA stratocumulus will develop and remain over the area, with cloud coverage greatest north and east downwind of the Great Lakes. At this time, lake effect snow showers appear poised down wind of the eastern Great Lakes, so we will keep a dry forecast going. There is an outside chance of a few flurries in our northeast zones if the cloud layer ends up intersecting the favored dendritic growth zone. It will be a cold day with highs ranging from 35 to 40. Finally, for Sunday night into Monday, mid level trough will progress east, allowing high pressure to build into the region. After a cold start in the lower to mid 20s Monday morning, highs will still only warm into the 35 to 40 degree range. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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VFR to start as high pressure departs east. That may change as a cold front now over NW Indiana crosses TAF sites tonight. Models predict MVFR ceilings for a few hours early tonight along and behind the front as showers develop. CVG and LUK may escape those conditions being farther from the bulk of moisture and forcing to the north. A return to VFR is forecast by Wednesday morning as high pressure builds back in from the west. Winds gusting over 20 knots this afternoon will start to subside this evening as mixing decreases with loss of daytime heating. Direction will shift from southwest to northwest with frontal passage, while speeds drop below 10 knots. OUTLOOK...No significant weather expected.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Coniglio/Hatzos SHORT TERM...Hatzos LONG TERM...Hickman AVIATION...Coniglio

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