023 FXUS63 KLOT 101906 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 206 PM CDT Wed Oct 10 2018 .SHORT TERM... 206 PM CDT Through Thursday... Numerous showers, moderate to heavy at times, are expected through the afternoon. There could be a few thunderstorms, but with only 500 J/kg per the latest RAP analysis, storms should be few and far between. Shear still looks favorable, but all other parameters are not favorable for severe storms, so I'm not expecting any severe storms. Showers shift east ahead of the approaching cold front ending from west to east early this evening. The front is over the Mississippi River and will shift overhead late this afternoon into tonight. Winds will become west and gust to 30 MPH immediately behind the front. Gusts increase to around 35 MPH this evening as we mix higher into the column. If mixing is greater than currently expected, gusts could be higher. Most areas have reached their high temp for the day and temperatures will continue to fall into the upper 30s to low 40s overnight. Windchills will be in the low 30s Thursday morning. JEE && .LONG TERM... 337 AM CDT Thursday through Tuesday... The main forecast concern during the extended period will be the increasing possibility of widespread frost across the area by the end of the week. Gusty west-northwesterly winds will continue on Thursday, and this will continue to usher in much colder weather. In fact, temperatures on Thursday are likely to remain in the upper 40s to low 50s area-wide in spite of mainly sunny skies during the afternoon. Temperatures Thursday night then look to fall into the lower to mid 30s with this cold airmass in place. There continues to be some concerns on the extent of frost across the area Thursday night, due mainly to the likelihood of a continued northwest wind of 5 to 10 mph through the night. However, with the possibility of some areas in north central IL and into the Fox Valley falling to near freezing, I have continued the mention of frost in the forecast to heighten awareness. Friday will be another cold day across the area, with upper 40s far north, to low 50s south. Model guidance has been indicating that a mid-level short wave disturbance will shift from the Dakotas to the southern Great Lakes during the day Friday. While this has been the case, guidance has been struggling on if there will be enough available moisture to support precipitation over the area as this disturbance moves overhead. With the uncertainty still apparent, I choose to run with the blended solution that gives some lower end chances for precipitation Friday afternoon and evening. Interestingly, some of the guidance indicating precipitation with this disturbance Friday evening are also cold enough to support some wet snowflakes. While this could be possible given the cold airmass in place, I have left the mention of snow out of the forecast at this time. Surface high pressure will be building in across the Mid- Mississippi Valley in the wake of this disturbance Friday night. If skies are able to clear late Friday night, we could see yet another night of temperatures falling down around freezing and potentially widespread frost over the area, assuming any lingering winds remain light enough. Temperatures look to remain chilly Saturday, but may warm a couple of degrees on Sunday, before another cold front pushes over the area later in the day. There still will be a chance of precipitation over the area late Sunday and Sunday night as forecast guidance continues to advertise another disturbance shifting across the central CONUS, but confidence remain low with the timing of this next system. KJB && .AVIATION... For the 18Z TAFs... Showers with a few embedded thunderstorms will continue through the late afternoon. I have low confidence in the number of storms as there is very little convective energy to work with. However, based on past observations, stronger showers and storms could bring visibilities down to IFR. Cigs should be mainly MVFR although a few patches of IFR cigs persist over northwest Indiana. Showers end ahead of the approaching cold front. The front is currently over the Mississippi River and will move through the terminals late this afternoon and early evening. There may be a very brief period of VFR conditions just ahead of the front, but MVFR cigs will return immediately behind the front. Winds will become west with gusts up to 25 kt initially. Better mixing behind the front may produce near 30 kt gusts by mid evening through Thursday morning. Gusts could be higher if mixing is deeper. West winds slowly diminish with gusts up to 25 kt expected in the late aftn as clouds slowly scatter out from south to north. JEE && .MARINE... 206 PM CDT A strong cold front will pass early this evening. Following the frontal passage this evening, wind gusts may briefly gust to near 35 kt gales, especially along the IL near shores, before gradually settling down to near 30 kt overnight and into Thursday. I think there will be a few gale force gusts, so I opted to go with a Gale Warning. However, winds should diminish below gales by mid Thursday morning. MTF/KB/JEE && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...LMZ742-LMZ743-LMZ744-LMZ745...9 PM Wednesday to 4 AM Friday. Gale Watch...LMZ740-LMZ741...9 PM Wednesday to noon Thursday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO