Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 210540 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 140 AM EDT Sat Apr 21 2018 .SYNOPSIS... An expansive area of high pressure will slowly drift east across the Great Lakes and Ohio Valley through the weekend. This will bring dry conditions and gradually warming temperatures. Low pressure will bring a chance of rain on Monday night into Tuesday, with rain remaining possible through the week as an upper-level trough moves into the region. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A few cirrus clouds skirting western CWA this evening will see them increase in coverage overnight, lowering slightly over northern portions of the CWA early Saturday. An expansive area of surface high pressure extending from the Great Lakes to the Mid-Atlantic states will remain over northern Ohio and keep a light and generally northeast wind over the CWA. As the light winds and and generally clear skies prevail, a good setup for radiational cooling conditions is expected overnight. However, there may be some thickening of high clouds, and winds may not go completely calm. A tiered approach has been taken to the frost/freeze headlines, as the warmer starting point will keep most of the areas from reaching lower than 32 degrees. There are also some thoughts that frost may not be widespread in the more marginal temperatures (32-36) due to a very dry airmass and winds of around 5 knots. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... On Saturday, surface high pressure will continue drifting east across the Great Lakes, keeping light flow in place over the Ohio Valley. There will be a continued increase in high and mid level clouds, as the 500mb ridge flattens and isentropic ascent aloft occurs. An area of low pressure in the southern plains is on track to move south of the Ohio Valley, and as a result, the ILN forecast area should remain on the north side of a surface boundary -- with winds remaining generally easterly to northeasterly through Sunday morning (and beyond). Despite the unfavorable winds, another day of (filtered) sun will allow for temperatures to warm into the upper 50s to lower 60s on Saturday. This remains below normal, but only by 4-8 degrees, which seems like a small departure compared to much of the past month and a half. As clouds increase, min temps on Sunday morning should range from the upper 30s to lower 40s -- likely with no significant chance for frost or freeze in the current program area. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Models continue to be consistent in pushing an upper level low out of southern plains and into the lower Mississippi Valley on Sunday. Any precipitation with the system stays to the south for Sunday. 12Z model rh fields are suggesting that the cloud cover on Sunday might be a less than forecast yesterday. This will allow temperatures to be a few degrees warmer, with highs ranging from around 60 in the north to the mid 60 and possibly the upper 60s in the far south. Upper low continues to shift eastward on Monday. While the GFS/ECMWF/Canadian bring some pcpn into northern Kentucky late Monday, the NAM is the outlier and pushes a band of QPF all the way through the fa. Will lean towards the majority forecast and will throw out the NAM solution. Kept slight PoPs in the south to cover the uncertainty. Expect highs on Monday to be in the mid 60s. Models left the upper low out of the Tennessee Valley beginning Monday night. As this occurs scattered showers should lift into the region. Kept chance PoPs through Tuesday night to cover the situation. Temperatures will be slightly below normal Tuesday and Wednesday with highs in the upper 50s. For the last half of the week, the extended models continue to show differences in the strength of H5 s/w dropping out the upper Mississippi Valley. The GFS and Canadian are much stronger than the ECMWF with this feature. Ran a blend to cover the uncertainty. Another s/w enters the Ohio Valley on Friday keeping the unsettled weather pattern across the region. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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Surface high pressure will remain across the southern Great Lakes through tonight. High and mid level clouds will spread down across the area through the day but VFR conditions are expected to prevail through the TAF period. OUTLOOK...MVFR ceilings will be possible Monday night into Tuesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES...
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OH...Frost Advisory until 9 AM EDT this morning for OHZ062-063-071- 072-078>082-088. Freeze Warning until 9 AM EDT this morning for OHZ064-065-073- 074. KY...Frost Advisory until 9 AM EDT this morning for KYZ097>100. IN...None.
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&& $$ SYNOPSIS...Hatzos NEAR TERM...Franks SHORT TERM...Hatzos LONG TERM...Sites AVIATION...JGL

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