Area Forecast Discussion
Issued by NWS Wilmington, OH

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980 FXUS61 KILN 210834 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 434 AM EDT Tue Mar 21 2017 .SYNOPSIS... Temperatures will be near seasonal normals today in the wake of a cold front which will push south away from the region. High pressure will build southward into the Great Lakes and Ohio Valley tonight, settling across the area on Wednesday. Much colder temperatures can be expected with this high. The high will move east Wednesday night into Thursday. After a cold start Thursday morning, temperatures will moderate through the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Dense fog has become expansive enough to warrant a Dense Fog Advisory for parts of the region, mainly along and north of I-70, which includes the Dayton and Columbus metro areas. Have issued the advisory until 9 am EDT. Winds will pick up toward morning, but it is unclear how fast this will improve the visibility before sunrise. For later today, low level moisture becomes quite shallow between 12Z and 15Z. Therefore, with daytime heating and turbulent mixing, we should see low clouds and fog lift and scattered out by afternoon. Unfortunately, there will be considerable mid and high level clouds in a northwest flow aloft, so peaks of sunshine will be limited. Models have backed off on the threat for a few showers across our southern CWFA late this afternoon into this evening in association with an embedded s/wv. It now appears that mid clouds will thicken with perhaps some virga occurring from the mid deck. Highs today will range from the lower 50s north to the lower 60s south.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... For tonight into Wednesday, a large scale mid level trough will dig southeast into southeast Canada/New England. A surface cold front associated with this trough will push south through the region overnight. This front is expected to be dry, and will mark the beginning of colder and drier air. Mid and high level clouds will decrease gradually overnight as north winds increase and become locally gusty in the 20 mph to 30 mph range. Low-level CAA will drop overnight lows from the lower 20s north to near 30 along and south of the Ohio River. On Wednesday, high pressure will build south into the Great Lakes and Ohio Valley. We should see a good deal of sunshine, with some mid and high level clouds increasing from the west late in the day. Despite the sunshine, a cold start and continued CAA will keep temperatures chilly for late March. Highs will range from the upper 30s north to the lower 40s south. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A fairly strong area of surface high pressure will be in place across the Great Lakes on Wednesday evening, providing a generally dry and cold air mass, extending southward across the upper half of the Ohio Valley. This will likely lead to Wednesday night being the coldest night of the forecast period, though there is some concern with some mid-level clouds potentially moving in from the southwest, at least across the southwestern half of the ILN CWA. However, as long as these clouds are not especially thick, the CWA should drop completely into the 20s -- with the potential for upper teens in outlying / rural areas in central Ohio. An amplifying 500mb pattern will be occurring even as relatively tranquil conditions are expected through Thursday, with heights rising as ridging builds over the Mississippi Valley. This will eventually lead to unsettled conditions through the Ohio Valley on Friday and Saturday. With upper/mid ridging moving into the region late Thursday into Friday, a warm advection pattern is expected to begin. This required a non-diurnal temperature trace for Thursday night into Friday morning, with min temps early in the overnight hours, and slowly rising temperatures by morning. As this occurs, some isentropically-driven precipitation is expected, mainly Friday morning. The feed of moisture transport, however, is weak -- and not strongly connected to the Gulf of Mexico. With marginal deep-layer moisture and most of the warm frontal forcing focused further to the north, there are no signs of heavy precipitation as of now, and PoPs have been kept on the low end of the scale. After this activity shifts north and east of the region, dry conditions are expected going into Saturday, with the ILN CWA expected to be in the warm sector of the developing system to the west. By Saturday afternoon and evening, attention will turn to a developing stacked low pressure center moving through Missouri. Confidence has increased in the overall timing and placement with this system, and it is now expected that there will be several rounds of showers (and potentially thunderstorms) along with this system -- running from Saturday evening through Sunday afternoon. As such, PoPs have been increased to the 50-70 percent range, with thunder kept in the forecast for Saturday afternoon, and a slight chance of thunder added for part of the area on Sunday afternoon. This system will have a respectable feed of theta-e and a tight/compact 850mb-700mb low, so forcing and moisture should be sufficient for widespread precipitation. The possibility for heavier rainfall or strong storms is less certain, owing to differences in model specifics and a pattern that is not necessarily a classic setup for either threat. Nonetheless, there is at least a low-end potential to watch and refine the forecast for in the next few days. A narrow ridge behind the stacked low will provide a reasonable chance for dry conditions for Monday, before unsettled conditions become more likely going into the rest of the week. The warming trend on Friday and Saturday is likely to bring temperatures into the 60s, possibly near 70 in the southern half of the CWA on Saturday, depending on when precipitation moves in. Near and behind the low on Sunday and Monday, temperatures will cool slightly, but should still remain above normal. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... Plenty of low level moisture remains across the region early this morning in the wake of exiting cold front. Aviators can expect IFR/LIFR/VLIFR conditions with the lowest conditions expected over by KDAY. There should be an improvement to the visibility between 10Z and 12Z as winds begin to increase from the north which will allow for some mixing. Otherwise, the low level moisture becomes fairly shallow after 12Z. Thus, with day time heating and turbulent mixing, IFR ceilings should lift and improve to VFR by 18Z as the low level moisture scatters out. For late this afternoon and this evening, a weak cold front will begin to push into the region from the north. Also, an embedded disturbance will move across the area. Mid clouds will thicken with the disturbance. Measurable precipitation is not forecast, although some virga may occur. For the overnight period, weak cold front will push south through the region. Its passage will be marked with a little bit of stronger winds with wind gusts in the 20 to 25 knot range. Much drier and cold air will filter into the Great Lakes and Ohio Valley with mid and high clouds shifting off to the southeast toward 12Z Wednesday. OUTLOOK...MVFR ceilings and visibilities likely Saturday along with a chance of thunderstorms. && .ILN WATCHES/WARNINGS/ADVISORIES...
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OH...Dense Fog Advisory until 9 AM EDT this morning for OHZ026-034- 035-042>046-051>056-060>062. KY...None. IN...Dense Fog Advisory until 9 AM EDT this morning for INZ050.
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&& $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Hickman

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