Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 200537 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 1237 AM EST Fri Jan 20 2017 .SYNOPSIS... Low pressure and a warm front will lift north across the Ohio Valley and the southern Great Lakes tonight and Friday. Warm, moist flow will then continue into the first part of the weekend. A stronger weather system will pass by to our south and southeast Sunday into Monday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Evening update blended temperature and dewpoint traces to observed values. Categorical area of rain will overspread the region this evening and had good timing which has not been touched. Rising temperatures expected overnight had no change to the min forecast, even as the future temperature values were adjusted ever so slightly. Prev disc follows -> Widespread showers are still forecast to pass north and northeast across the region tonight. This precipitation will be associated with a warm, moist, low level convergent jet axis. Temperatures will bottom out early, then slowly climb overnight as a surface warm front approaches the Ohio River Valley. && .SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/... A blend of high resolution models, along withe the 12Z GFS and 12Z ECMWF, have been used to compose the short term forecast. Widespread showers will taper off from southwest to northeast Friday as the low level warm, moist convergent jet axis shifts northward into the Great Lakes. Rainfall amounts will generally range between 0.50 and 1.00 inches. A surface warm front will lift north across the area during the day. Considerable low level moisture will remain, so not much is expected in terms of sunshine. High temperatures will be much above normal, ranging from the mid 50s to the lower 60s. For the period Friday night into Saturday night, broad, warm, moist flow will continue. Models suggest a few embedded impulses within a southwest flow aloft will trigger a few showers Friday night, and then again Saturday afternoon and Saturday night. There could be enough instability along and south of the Ohio River and across our western zones for a rumble of thunder Saturday afternoon and evening. The chance appears to be very low at this point, so will persist with just showers for now. A somewhat non- diurnal trend in temperatures have been employed. Highs in the upper 50s to the lower 60s on Saturday will only drop into the upper 40s and lower 50s by Sunday morning. These values will continue to be much above normal for what is considered the climatological coldest time of the year && .LONG TERM /SUNDAY THROUGH THURSDAY/... On Sunday, a fast-moving upper level low pressure system is expected to move across the southern tier of states. After a day of southerly flow on Saturday, antecedent conditions will be warm and moist in the Ohio Valley, but a shift in winds to easterly will put an end to any further warm advection. However, temperatures are only expected to drop slightly from Saturday to Sunday, especially as the day now looks slightly drier than previously thought. Both the ECMWF/GFS suggest that the ILN forecast area will be well north of the widespread rainfall developing across the Tennessee Valley region. As the low moves ENE going into Monday, and with precipitable water values continuing to remain high for January (near or just under an inch), an increase in rain chances will eventually occur through Monday and Monday night -- especially in the eastern half of the forecast area. Overall model differences with respect to timing are small (when considering longitudinal position) but placement of the low / forcing / precipitation remain a little less clear. Once the low has moved from south of the region to southeast of the region, a switch to northerly flow will allow for a gradual drop in temperatures through Monday and Tuesday. Generally dry conditions are expected on Tuesday, as a narrow ridge arrives into the area. Forecast specifics become less certain by Monday night and Tuesday, with GEFS 500mb height plots showing a wide range in both amplitude and timing of the ridge (and the next wave following behind it). What appears fairly certain is that warmer-than-normal conditions will continue through Wednesday, before a cold front moves through the area at some point on that day, helping to bring in some colder air for the end of the week. Confidence is low with regards to precipitation chances with this front, as GFS/ECMWF suggest it will be lacking in deep moisture. With broad troughing over the Great Lakes and Ohio Valley on Thursday, some light precipitation may develop -- and temperatures during the low end of the diurnal cycle may be cool enough to support some snow. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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An area of low pressure will move over the TAF sites this morning providing widespread showers across the area. CIGs will continue to fall to IFR this morning with some LIFR possible. Rain will then come to an end across the area around 12z this morning with high res models in fairly good agreement. During the day today surface low pressure will head north of the area with winds veering towards the southwest. CIGs should recover slightly to MVFR this afternoon but stout low level moisture will keep ceilings in place. Saturday morning another area of low pressure will organize across the midwest allowing winds to take on a more southerly component. Thanks to continuing low level moisture more IFR cigs will be possible Saturday morning OUTLOOK...MVFR/IFR ceilings possible into Saturday, and then late Sunday into Tuesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Franks/Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Haines

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