Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 201054 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 654 AM EDT Mon Mar 20 2017 .SYNOPSIS... Low pressure and its associated cold front will track southeast across the southern Great Lakes and Ohio Valley today into tonight. The front will continue to move south of the area on Tuesday as cooler air begins to filter into the region from the north. An embedded upper level disturbance may bring the threat of showers to parts of the area late Tuesday into Tuesday night. High pressure and much colder air will then arrive by Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Low pressure and its associated cold front will track southeast across the southern Great Lakes and Ohio Valley today into tonight. Our region will first have to deal with an initial shot of convection this morning out ahead of the front. A low level jet focused over northern Illinois/northern Indiana will result in showers and embedded thunderstorms for the remainder of the overnight hours. In fact, radar mosaic indicates that this convection is underway. High resolution/convective allowing models are still indicating that this convection will slip south/southeast into the western parts of the forecast region by morning. Thus,have likely and/or categorical pops for west central Ohio, the Whitewater and Miami Valleys, and parts of the Tri-State. Convection is expected to wane/dissipate by late morning as it moves south into retreat drier air as well as a lull in low level forcing. For this afternoon, surface low pressure and cold front will approach from the west. A low level, convergent jet will get going once again between 18Z and 00Z. This will result in showers and embedded thunderstorms erupting across northern Indiana and northwest Ohio. Given the focus of the low level forcing, this convection is expected to move east/southeast into the northern zones by mid afternoon into early evening. Temperatures will be very tricky today given two rounds of precipitation, cloud cover, and WAA ahead of the low. A consensus approach has been employed, which ranges highs from the lower 50s north to the lower/mid 60s far south and southwest. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Showers and embedded thunderstorms will be making their way southeast this evening. Main coverage is still poised for our east/northeast where better low level forcing will be located. There maybe a trailing tail of likely PoPs extending into at least the Cincinnati metro area out ahead of the front. Precipitation will wane from northwest to southeast overnight as the cold front slips southeast through the region. Lows will range from the upper 30s north to the upper 40s south. On Tuesday, the front will continue to push south from the region. Considerable cloudiness will remain due to low clouds in the morning, and then mid level cloudiness spilling into the region from an approaching embedded s/wv in the northwest flow aloft. This feature may bring a few showers to southern locations late in the day. Highs will range from the lower 50s north to the upper 50s south. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A deep upper trough will be moving through eastern Canada on Tuesday evening, with its influence pulling away from the Ohio Valley. As this occurs, the ILN CWA will be in between two surface boundaries. One will be well south of the area and gradually moving away, while another will be moving south from Michigan. Attention will turn upstream to precipitation development over the middle Mississippi Valley -- focused on the south side of a 300mb jet, and focusing along a sharp 850mb theta-e gradient south of the ILN CWA. There has been a southward trend across all models with regards to the precipitation with this system, so PoPs have been lowered slightly, now generally in the 20-40 percent range for only the southern half of the ILN CWA. The second surface boundary is expected to move south through the region between 03Z-12Z, and while it is not expected to produce additional precipitation, model soundings suggest it will mix the boundary layer and lead to some 20-25 knot wind gusts behind its passage. Behind this boundary, a much colder air mass will briefly move into place across the upper Ohio Valley and southern Great Lakes. With continued northeasterly flow on Wednesday, as the high centers over Michigan, cool temperatures are expected even with clouds mostly anticipated to clear out. An amplifying 500mb pattern will be occurring even as relatively tranquil conditions are expected Wednesday and 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 Friday, a warm advection pattern is expected to begin, with isentropically-driven precipitation, mainly early Friday morning. No signs of heavy precipitation as of now, and PoPs have been kept on the low end, with most of the warm frontal forcing remaining further to the north. Overall, this activity will shift north of the region during the first half of Friday, with dry conditions expected going into Saturday. From there, attention will turn to a developing cold front and surface low pressure center further to the west, potentially affecting the area on Saturday. Still seeing way too wide an array of possible solutions to try to pin down exactly how the front/low will play out over the Ohio Valley and Great Lakes, and if any chance for stronger storms may exist during the end of the forecast period. It does look like the Saturday evening time frame may have the greatest precipitation chances, based on a compromise of 18Z/00Z GFS and 12Z/00Z ECMWF solutions. However, the timing differences are still great enough to keep PoPs for any specific time frame limited to 50 percent. After cooler temperatures in the cold advection on Wednesday, a warming trend (mainly diurnally driven) is expected going into Thursday, strengthening further as warm advection kicks in for Friday and Saturday -- with both days expected to see highs in the 60s. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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Showers and a few embedded thunderstorms will affect the western terminals through 16Z. Given elevated nature of the storm, only pockets of MVFR conditions are expected. By late this morning, convection will continue south and eventually dissipate as it moves into retreating dry air. For the remainder of the afternoon, focus turns toward our northwest. An area of low pressure and a cold front will be moving east/southeast to our region. Again, most models concur that showers and embedded thunderstorms will get going across northern Indiana and northwest Ohio. This precipitation will be fed by another developing low level jet and low level convergent flow. For now, the best chance for rain showers/embedded thunder is poised for the northern terminals. KCVG/KLUK will be on the edge of the likelihood of precipitation. MVFR conditions will develop in the precipitation. As the front slips by to the south, cooler air and an increasing subsidence inversion will lower ceilings into the IFR category. Most precipitation should end after 06Z across our south as the front continues to move away. Some MVFR mist may develop behind the front as well. OUTLOOK...MVFR/IFR ceilings and MVFR visibilities expected Tuesday morning. MVFR ceilings and visibility`s possible Friday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Hickman

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