Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 160557 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 1257 AM EST Fri Feb 16 2018 .SYNOPSIS... Widespread showers will push across the area tonight into Friday as a slow moving cold front interacts with a very moist airmass. High pressure and drier, colder air will arrive for Friday night. More precipitation is expected Saturday when low pressure is forecast to travel across the Southern Appalachians. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Ahead of a cold front that is currently just outside the ILN CWA to the northwest, continuous southwesterly flow is continuing to moisten the atmosphere, with widespread rain (and embedded heavy showers / a few thunderstorms) now impacting the forecast area. The 00Z KILN sounding showed an atmosphere with little in the way of instability, but just enough to allow for some convective development within the regime of LLJ convergence. A broken line of convection in southern Indiana will eventually impact much of the southern half of the ILN forecast area. Individual storm motions are generally west-to-east while the line is more oriented WSW-to-ENE, but some elements within the wavy line of convection (including some moving through the west-central sections of the forecast area right now) are more parallel to the flow. This will allow a continued threat of prolonged moderate to occasionally heavy rainfall, and some additional flood advisories will likely be needed as the night progresses. Still a chance of some flood warnings depending on the orientation of the convection. Winds have yet to become an issue, with a noted loss of momentum in the lowest 1kft of the atmosphere (as per TIDS/TDAY radar data) keeping the stronger flow from reaching the surface. Previous discussion > Atmospheric river extending from the Eastern Pacific to the Ohio Valley evident on Channel 10 of GOES-16 is the source of moisture leading to our weather problems. Heavy rain is expected due to near record PWATs being lifted along the slow moving cold front that is nearly parallel to the potent mid level flow. Widespread rain showers that have developed out ahead of the cold front are impacting northern portions initially, before moving south across the area this evening through tonight as the front sags southeast, pushed by the strengthening mid level jet. Efficient rain processes will lead to one to locally two inches of rain falling on saturated ground, causing localized flood problems. Therefore, Flood Watch remains in effect through Friday afternoon. Kept chance of thunderstorms through this evening for convection forming in an atmosphere containing up to 500 J/KG CAPE. Supported by strong veering wind fields, marginal risk for severe thunderstorms is being limited by the rather low instability. Very warm temps in the 60s this evening will fall off overnight as the cold front moves in, with readings by 6 am ranging from the mid 30s over West Central Ohio, to the 40s in metro areas, up to around 50 far southeast. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Cold front containing near record PWATs will be near the southern border of the FA Friday morning. Most heavy showers will have ended, but lighter showers should linger into the afternoon especially in southern locations. Flood watch continues until 2 pm for localized high water problems, while runoff not mitigated by vegetation arrives in streams that will undergo rapid rises. The showers behind the cold front should be out of the FA by Friday evening, and 1029 mb high pressure traveling through Northern Ohio is forecast to bring dry weather Friday night. Temperatures will show a non-diurnal decreasing trend Friday in strong cold advection on a northwest low level flow. This will yield readings in the mid and upper 30s most locations by Friday afternoon, a 30 degree drop in 24 hours. Lows in the 20s are forecast for Friday night. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Approaching s/wv energy in the quasi-zonal flow aloft will perturb a weak wave of low pressure to our southeast along old frontal boundary on Saturday. The s/wv will combine with upper level divergence from the RR quad of an upper level jet, allowing precipitation to spread northeast through the day. A weak boundary to our west may also aid in some precipitation development. In all, highest PoPs are still slated for our southern/eastern zones, with lower PoPs northwest. It will be cool on Saturday, 30s to lower 40s. Some of the precipitation may be a rain/snow mix, especially north. This mix will be highly dependent on the rate of precipitation and the degree of the web bulb effect/evaporative cooling to lower the freezing levels. Some minor accumulations of a tenth or two could accumulate on grassy surfaces late in the day and into the evening. For Saturday night, energy will quickly push east, allowing the precipitation to come to an end by midnight. Skies will become partly cloudy with lows in the upper 20s to the lower 30s. Sunday will be the least active weather day in the extended as high pressure traverses the Ohio Valley. Under sunshine, highs will moderate into the 40s to lower 50s. Models continue to advertise an active weather pattern for next week. Thus, the threat for additional flooding will continue. The upper level flow pattern becomes amplified as a strong subtropical ridge builds off the southeast U.S. coast while large scale mid level troughing develops across western Canada/western U.S. This setup will transport rounds of moisture northeast across the Great Lakes and Ohio Valley. The first round is expected Sunday night into Monday as a low level/moist jet in association with a warm front pushes northeast across the area. In the warm sector, highs will warm into the 60s most locations on Monday. For Monday night into Wednesday night, a very slow moving frontal boundary will be the focus for more rounds of precipitation. It will be unseasonably warm on Tuesday with some cooler air slowly moving back in by Wednesday. By weeks end, there could be a respite in the probability for precipitation by Thursday as front tries to move east/southeast of the region. However, activity may ramp up again by Friday and into next weekend as s/wv energy begins to affect the Great Lakes and Ohio Valley once again. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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Rain will continue through the overnight hours before tapering off during the day on Friday. Cigs will typically be between VFR and MVFR, however some isolated lower cigs will be possible. Visbilities will be reduced with some of the rain. Winds will pick up and gust at times on Friday before decreasing Friday evening. OUTLOOK...MVFR conditions are possible on Saturday and Monday into Tuesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES...
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OH...Flood Watch through this afternoon for OHZ043>046-051>056- 061>065-071>074-079>082-088. KY...Flood Watch through this afternoon for KYZ100. IN...None.
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&& $$ SYNOPSIS...Coniglio NEAR TERM...Coniglio/Hatzos SHORT TERM...Coniglio LONG TERM...Hickman AVIATION...Novak

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