Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 061435 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 935 AM EST Tue Dec 6 2016 .SYNOPSIS...
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An area of low pressure will move northeast through the Ohio Valley today. Drier conditions will return on Tuesday, but temperatures will drop for the second half of the week after a cold front moves through on Wednesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Surface low in middle Tennessee will continue to lift northeast through the day. Large shield of rain to the north of the low will persist into the afternoon and then start to clear from west to east later in the day. Temperatures will struggle to rise with daytime highs less than 5 degrees warmer than mid morning readings.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... Aside from the low clouds, the rest of the air mass in place over the Ohio Valley tonight will be quite dry. On the southeastern periphery of a stacked low over northern Minnesota, a dry cold front is expected to move through the ILN CWA early Wednesday morning, with winds switching to the WNW. The surface reflection of this front is not overly easy to pick out, and in fact, surface winds are expected to back to the SW again by Wednesday afternoon. The cold advection will do its best to stunt the diurnal cycle, and much cooler conditions are expected going into Wednesday night. By Thursday, the slowly-moving longwave pattern feature troughing setting up across the western Great Lakes, with very quick WSW flow aloft over the Ohio Valley and mid-Atlantic. Previous forecasts have mentioned the possibility of snow on Thursday morning, but models continue to back away from this proposition, with both the 00Z GFS / 00Z ECMWF keeping conditions dry across the ILN CWA. While a 20 PoP for a slight chance of light snow has been maintained, a mention of flurries might eventually cover the scenario. There are no signs of forcing in the low levels at all, with only some weak/transient upper support on the south side of the 300mb jet, and this no longer appears to be enough to generate any reasonable chance of accumulating snow. The continued cold advection just off the surface will keep the shallow boundary layer well mixed through Thursday and Friday, which does present the possibility of a persistent (though maybe broken) stratocumulus deck. As the top of this mixed layer intersects the lower end of the DGZ on Friday, some flurries may be possible (particularly in the northern half of the ILN CWA). This has been included in the forecast. Until the advection pattern really starts to adjust itself over the weekend, temperatures will only continue to cool each day this week. Model blends for temperatures looked generally reasonable, but NAM min temps appeared too high for the latter half of the week, and were not used. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... With the upcoming weekend, a warm front will cross northeast through the Ohio Valley and increase the threat for rain on Sunday, possibly a rain/snow mix as the warm air overspreads the cooler air in place. Models continue to disagree in how this system evolves with the ECMWF notably drier and further west than the more progressive and much wetter GFS. Modelers from WPC also seem to have split the difference here noting the warm frontal passage similar to the GFS solution on Sunday, then bows to the ECMWF on Monday morning with the surface low east of Lake Superior. GFS occludes the front off of the east coast on Monday morning and pushes in drier air. Meanwhile the ECMWF continues to keep a strong baroclinic zone in the midwest with continued threat for precipitation over the Ohio Valley during this same time frame. Tried to trend lower on the threat for precipitation on day 6 and 7 and culminated the pops on the high end category Sunday afternoon, in line with the GFS. Against better judgment and nodding towards ECMWF the pops have been lingered into Monday and Monday night to account for lower confidence and natural variability of the models on day 7. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/...
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IFR ceilings will spread in the Columbus area leaving all TAF sites IFR. Rain will end late around 20-21Z for the wrn tafs and a few hours later for the ern tafs. Behind the cdfnt, winds will turn to the w and will increase, with gusts of 20 kts possible. Cigs will try to lift to MVFR in the w behind the front, but the should linger in the IFR range further e. Some drizzle will be possible during the late afternoon and evening hours of Tuesday as the forecast soundings are showing drier air aloft coming in over the trapped low level moisture. The low level moisture will finally begin to scour out aft 12Z Wednesday. OUTLOOK...MVFR ceilings are possible again on Thursday and Friday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM... SHORT TERM...Hatzos LONG TERM...Franks AVIATION...Sites

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