Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 111432 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 932 AM EST Wed Jan 11 2017 .SYNOPSIS...
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Warm and moist air will move into the region this afternoon. Rain will be possible at times through Thursday, when another cold front is expected to move through the area. This frontal boundary will stall in the vicinity, leading to continued chances for precipitation through the weekend.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Showers near the Kentucky-Tennessee border will continue to move northeast and track across the forecast area this afternoon. Still looks like there could be some embedded thunder with this. Forecast highs look reasonable at this point.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... The active weather pattern will remain quite so through the next several days, heading into a weekend with the potential for wintry precipitation impacts. Continued warm advection tonight through Thursday afternoon will lead to a continual slow rise in temperatures. As this is occurring, significant/intense frontogenesis will occur between two strong areas of surface high pressure. This developing front will become very well defined by late Thursday morning, extending from south-central Oklahoma to Lake Erie. The front is forecast to move east / southeast through the ILN CWA during the afternoon, with just enough moisture and elevated instability ahead of it to allow for a brief window where convection could occur. With focused forcing along the surface front, the greatest chances for precipitation should be fairly focused, especially as deep-layer forcing and moisture appear to be somewhat lacking. Dry conditions are expected immediately behind the front, which is forecast to pivot to a WSW-to-ENE direction by Friday morning. A complicated forecast will then set up for Friday and Saturday, with the surface boundary remaining south of the ILN CWA, leading to entrenched cool temperatures near ground level -- near or below freezing during the low end of the diurnal cycle. However, within the 850mb-700mb layer, flow aloft will remain west-southwesterly and somewhat warm. The end result will be a strong and saturated inversion between 950mb and 825mb, with a shallow layer of cold air below it. This thermodynamic profile is one that would support, from south to north, the possibility of any of the four main precipitation types in the ILN CWA -- rain, freezing rain, sleet, and snow. However, the greatest concern will be the chances for freezing rain, especially on Saturday morning. There is reasonable model agreement, excepting the 00Z GFS perhaps, that most of the ILN CWA will remain dry on Friday. Precipitation will be focused south of the area, but some light rain / freezing rain may get into the southern counties during the morning -- before conditions warm enough to allow for rain during the afternoon. Remaining stagnantly in a favorable area for lift with respect to the 500mb/300mb wind flow, precipitation development will continue to be favored along the low-level boundary, and on Saturday morning this activity will move far enough north to allow for more significant precipitation over the near-surface cold layer. Confidence in the general setup for accumulating ice on Saturday morning is high, particularly in the west-central section of the ILN CWA. Confidence in the exact timing/placement/QPF magnitude is moderate, but confidence in the exact strength of the warm layer is low -- NAM/ECMWF/GFS projections show a significant spread in the magnitude of the max temps through the lowest 3km. This significantly limits the amount of certainty in the magnitude of the event, and makes any sort of specific forecast of amounts impossible at this stage of the forecast cycle. However, there does appear to be enough in the model/pattern signal to explicitly forecast freezing rain in the grids, and include a somewhat-generic mention in the HWO. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... Precip may end Sunday when the boundary is shown to sag southward in response to short wave energy that will tilt the upper flow to northwest, while surface high pressure builds across the Great Lakes. Rain may then return on Monday and Tuesday, though the latest ECMWF guidance points to a drier solution as opposed to model blends that show persistent precip. Near normal mid winter highs mainly in the mid and upper 30s are indicated for Friday and Saturday when an easterly low level flow will carry cool air. Much warmer than normal temperatures return by Monday and Tuesday when highs may reach the 50s most locations. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... For today, VFR conditions will be short lived. In a west/southwest flow aloft, a low level jet associated with an embedded disturbance will result in warm, moist ascent which will develop/spread showers into the region this afternoon. It looks like better instability remains to the west over Illinois and Indiana, but still can not rule out a rumble of thunder. The probability is about 20 percent, so will continue to leave out of the TAFs. Models concur that ceilings will lower into the IFR category with MVFR visibilities in showers. In addition, as low pressure approaches the western Great Lakes, the pressure gradient will tighten, allowing winds to increase from the south. Winds will also become gusty up to 25 knots. Showers will taper off late this afternoon and evening from southwest to northeast. Ceilings in the MVFR/IFR category will remain. Low level jet will increase in speed, which poses another LLWS threat. This has been placed in the terminals. South winds will remain stiff and gusty. For tonight, another embedded disturbance along with low level moist, convergent flow will spread showers back into the region from the west/southwest. Best instability appears to remain northwest of the terminals, although a rumble of thunder may still occur. Breezy south winds 12 to 18 knots with gusts between 25 and 30 knots will continue. OUTLOOK...MVFR/IFR ceilings and MVFR visibilities likely Thursday into Thursday night. MVFR/IFR ceilings and MVFR visibilities are possible at times Friday through Sunday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM... SHORT TERM...Hatzos LONG TERM...Coniglio AVIATION...Hickman

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