Area Forecast Discussion
Issued by NWS Wilmington, OH

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209 FXUS61 KILN 192017 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 317 PM EST Thu Jan 19 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 FRIDAY MORNING/... 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 FRIDAY 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 /20Z THURSDAY THROUGH TUESDAY/... IFR/MVFR cigs continue to linger across the Central Ohio tafs, but the srn edge is advancing northward and they should break out to VFR in the first hour or so of the taf period. Meanwhile high clouds are advancing quickly northward. A H5 s/w will lift north across the tafs tonight. The combination of pva and isentropic lift will create a large area of rain which will reach the srn tafs around 00Z. Cigs and vsbys Will drop to IFR as the evening progresses. The rain will end from s to n between 12Z-15Z on Friday, however low cigs and vsbys in fog will linger for the remainder of the taf period. OUTLOOK...MVFR/IFR ceilings possible into Saturday, and then late Sunday into Monday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Sites

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