Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 260206 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 1006 PM EDT Sun Jun 25 2017 .SYNOPSIS... After an isolated evening shower, surface high pressure will bring dry weather and cool temperatures tonight. An upper level trough swinging through the Great Lakes will bring a chance of showers and thunderstorms Monday afternoon into early Tuesday. High pressure will provide dry weather at midweek with increasing precipitation chances toward the end of the week as temperatures warm to near normal. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Pronounced troughing with embedded disturbances rotating about the larger-scale low continues across the Great Lakes and Ohio Valley regions. Regional obs indicated that the very weak surface boundary that had provided initiation for isolated showers earlier has since moved to approximately parallel to the Ohio River. The showers were diurnally-enhanced and with sufficient/significant dry air throughout the column /as sampled by the KILN 00z sounding/ do not expect much in the way of additional redevelopment through the near term period. As such, have kept the fcst dry for all areas. Behind this frontal boundary, a very weakly-defined broad surface high pressure will build into the FA, allowing for light winds and mainly clear skies through the overnight period. Some scattered AC across the north will slowly dissipate through the near term period, with many locations beginning the day on Monday with clear/mostly clear skies. With relatively dry air in place and mainly clear skies, another unseasonably cool night is in store for the FA, with lows expected to bottom out in the low/mid 50s area-wide. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Next mid level shortwave to drop southeast, sharpening up the mean trof over the region Monday night. 25-30kt low level jet, along with marginal instability may lead to a few rain showers or isold thunderstorms into the west Monday afternoon. Will limit pops to chance category. Temperatures look to be around 10 degrees below normal with highs Monday in the lower and middle 70s. Expect this precipitation to drop southeast across ILN/s FA Monday night ahead of a surface cold front. Thunder chances will diminish as very weak instby decreases. Cool temperatures to drop to lows in the lower and middle 50s Monday night. && .LONG TERM /TUESDAY THROUGH SUNDAY/... On Tuesday morning, large-scale troughing will remain in place over the eastern half of the CONUS, with a relatively dry air mass in place from the upper Ohio Valley through the mid-Atlantic. Attention over the middle Ohio Valley will be focused on a shortwave trough, moving ESE through the overall flow. The axis of this trough will likely not quite be cleared through the ILN CWA by 12Z Tuesday, with some chance of showers remaining in place near the Ohio River and lower Scioto Valley through the morning. By afternoon, with subsidence behind the shortwave, high pressure at the surface will begin to take hold over the region. This will be too late to allow a significant rise in temperatures, with below normal conditions expected, especially in central Ohio. Dry high pressure is expected to remain in control of the weather from late Tuesday through early Thursday, influencing conditions through the middle part of the week. With a turning of winds to the south on Wednesday, a more appreciable warmup will begin, with temperatures returning to the 80s. As a more progressive pattern begins to set up for Thursday and beyond, model differences become more pronounced, leading to lower confidence -- especially in precipitation timing near the end of the week and into the weekend. There is agreement that a frontal zone will set up east-to-west across the southern Great Lakes beginning early Thursday, with the ILN CWA in the warm sector within solid deep-layer southwesterly flow. As convection develops at the north end of this warm sector, and along the frontal area, there will eventually be some propagation downstream which should impact the ILN CWA -- likely beginning on Thursday afternoon, and then again as additional waves of precipitation occur going into Friday. How much of the CWA remains capped is a question, as is the exact position of the front. However, model runs have trended a little southward with precipitation chances, increasing the probability for storms in the ILN CWA on Thursday and Friday (especially in the northern half of the CWA). PoPs have been increased slightly through this time period, but with little change to temperatures, as there is confidence in continued southwesterly flow through the period. In addition, with ample instability and at least somewhat favorable deep-layer shear, some strong to severe storms could be possible on Thursday and Friday. Differences in the evolution of an upstream trough going into the weekend will preclude more than very low confidence in the forecast Saturday into Sunday. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Diurnally-driven VFR Cu coverage will decrease early in the TAF period, yielding mainly clear skies for the overnight period. Gusty WNW winds will also subside towards sunset, with light winds of around 5kts expected past 01-02z through mid-morning Monday. With the wind not expected to go completely calm, and the presence of quite a bit of dry air in the low levels, do think that VSBY restrictions will be difficult to come by at KLUK. Past 18z Monday, increased moisture ahead of an upper-level S/W and a weakly-defined surface frontal boundary will allow for a VFR deck to gradually overspread the terminals towards the end of the TAF period. Although quite a bit of dry air will remain in the lower levels, there should be enough lift associated with the aforementioned features to generate isolated to scattered light SHRA after 18-21z. Although coverage will likely remain scattered at best, expect that activity will shift south/east through the area towards the end of the period as the front progresses southward, eventually affecting KCVG and KLUK as well. Have held off on inclusion of a VC for now at these terminals until placement and timing becomes a bit more focused. Altho instby will remain quite limited, cannot completely rule out a TS with aft/eve activity Monday. This being said, have omitted from TAFs at this time until placement and coverage becomes better defined. WNW winds will increase to around 10 to 12kts during the day on Monday, with a few gusts to 20kts possible. OUTLOOK...Showers and thunderstorms are possible Thursday and Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...AR NEAR TERM...KC SHORT TERM...AR LONG TERM...Coniglio/Hatzos AVIATION...KC is the U.S. government's official web portal to all federal, state and local government web resources and services.