Area Forecast Discussion
Issued by NWS Northern Indiana

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279 FXUS63 KIWX 051740 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 1240 PM EST Mon Dec 5 2016 .SYNOPSIS... Issued at 1235 PM EST Mon Dec 5 2016 Clouds will linger through tonight with areas of fog possibly developing tonight in areas where snow remains. A weather system will spread some rain across the area Tuesday, with the greatest coverage expected along and east of the Interstate 69 corridor. A brief period of some light snow is possible at onset on Tuesday, but little or no snow accumulation is expected. Much colder air will spread over the area Thursday with lake effect snow developing. Highs will be in the 30s through Wednesday, then in the 20s Thursday and Friday. Lows will be around 30 tonight then falling into the teens later this week. && .UPDATE... Issued at 1053 AM EST Mon Dec 5 2016 Near term challenges will continue to center on temp trends and fog potential. Downward trends in vsbys have been noted west of the forecast area across much of northwest and north central Illinois in association with better snowpack. As low level anticyclone progresses eastward this afternoon, some concern that fog could spread eastward, particularly across far northwest portions of the area. Currently not expecting any dense fog at this time and may need to add mention of patchy fog with late morning update. Perhaps better potential of fog for particularly northwest half of the area for tonight as slightly better near sfc moisture wraps into the area on northwest periphery of this anticyclone, with some effects from lingering snowpack. Otherwise, a very strong low level inversion should persist through the day keeping low clouds in place. Temps not likely to recover much, especially across snow covered areas where highs at or just above freezing are more likely. May need to make a slight downward adjustment in temps for a few spots, but otherwise trends from previous forecast remain intact. && .SHORT TERM...(Today and Tonight) Issued at 422 AM EST Mon Dec 5 2016 Have maintained a mention of some fog today over west areas, mainly west of highway 31 given some of the high resolution/WPC models and upstream fog development over western Illinois. Given abundant cloud cover and some fog, have cut high temps a few degrees over these areas. Otherwise, the cloud cover will linger through tonight. Some light precipitation is possible late tonight over southern areas ahead of the next system. It looks like any travel issues through tonight should be at a minimum given temperatures holding near freezing tonight. && .LONG TERM...(Tuesday through Sunday) Issued at 422 AM EST Mon Dec 5 2016 A number of weather systems this period are expected to produce a variety of weather across the forecast area through this week. An upper low will eject northeast Tuesday. This system will become more of an open wave then earlier expected and track farther southeast than earlier expected. This will limit precipitation Tuesday. Given this track, and thermal profiles, continued to trend back snow accumulations. The limited upper motion and a warm layer will also limit snowfall. At this point, some light wet snow accumulations are possible over mainly grassy areas Tuesday. Much colder weather will follow Thursday. The ECMWF continues a weakening of the wave and subsequent snow Wednesday night. Kept a small chance of snow with this system before much colder air arrives Thursday. Lake effect snow will develop Thursday as much colder air spreads over the relatively warm waters of Lake Michigan. Delta T values over 20C at 850 mb with a northwest flow will favor snow accumulations over far southwest Lower Michigan into northwest Indiana. Lake effect snow will diminish from late Friday into early Saturday as winds back to the southwest. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon) Issued at 1229 PM EST Mon Dec 5 2016 Satellite/obs trends show stratus will likely hold strong with limited hope of at least partial clearing. A few of the high res models have been persistent on cigs lowering somewhat tonight, but more with visibilities dropping to LIFR at KSBN and more MVFR at KFWA. Other models show little or no impact, likely from mixing below the inversion. Will be a tough call how this unfolds with winds in the 5 to 8 kt range not normally the most conducive to fog development. After coordination will introduce fog tonight, dropping to 3/4SM at KSBN at times to start a trend and more conservative 3 miles at KFWA. Next system will be arriving on Tuesday, keeping clouds in place with some precip chances at mainly KFWA. For now have left any mention out. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ UPDATE...Marsili SYNOPSIS...Murphy SHORT TERM...Skipper LONG TERM...Skipper AVIATION...Fisher Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana

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