Area Forecast Discussion
Issued by NWS Chicago, IL

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000 FXUS63 KLOT 230750 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 150 AM CST Thu Nov 23 2017 .SHORT TERM... 100 AM CST Through tonight... A few echoes on radar from the streaming in from the northwest. Very dry sounding earlier in the evening from DVN is consistent with little to nothing hitting the ground. There is some shortwave energy riding the NW flow that will get out of here in the coming hours, and with the surface reflection weak and the frontal boundary also weakening, expect little more than some lowering cloud bases and maybe some brief mixed precipitation. This wave will depart at or even before daybreak. The surface low will further weaken to our west leading to a mostly sunny Thanksgiving Day under light to moderate southwest winds, which will make for a milder day with highs in the lower 40s. KMD && .LONG TERM... 100 AM CST Friday through Wednesday... The next system to pass through the region is off the PacNW coast. This will ride the ridge north into Canada before diving southeast through Wisconsin late Friday. This system gives us more of a glancing blow than the last front did on Tuesday. With another impressive low across Canada, warm southwest winds will make for a warm late fall day, and have continued the idea of temperatures above the blended guidance and on the higher side of ensemble guidance which would bring mid to upper 50s nearly area wide with mixed cloud cover. The 12z EC was the only guidance bringing any precipitation with this front and we may be able to push out some very light rain/sprinkles, but most of the 0z model suite is largely dry. High pressure will fill in for the weekend, making for sunny and near seasonal temps. We will still see a cool down on Saturday and Sunday, but much more tempered this go around. A weaker wave will pass through south central Canada Monday, another day where southwest winds should usher in warm temperatures similar to Friday where the model blend appears like it could be too cool. Eventually an upper trough will organize across the west at a bit farther south latitude, but guidance is still mixed as to the impacts from this. The pattern looks somewhat progressive beyond this, but at this point overall precip chances are not too high, just the continued up and down temperature see-saw. KMD && .AVIATION... For the 06Z TAFs... Quiet aviation weather will persist through the period, with mainly VFR mid-high clouds into Thursday morning. High pressure was drifting southeast across the Ohio Valley late this evening, with light south-southwest wind across the terminals. A dissipating cold front across the Upper Midwest will becoming ill-defined as it moves into northern IL around midday on Thursday, briefly turning winds a bit more westerly, though speeds less than 10 kts are expected to prevail. Mid-level ceilings in the 7000-9000 foot range will persist overnight and Thursday morning, before clouds scatter early in the afternoon. Ratzer && .MARINE...
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150 am...A large area of high pressure over the Ohio Valley will move to the mid Atlantic by Friday morning as it slowly weakens. Strong low pressure will move across Ontario Friday and into Quebec Friday night. A trailing cold front from this low will move across Lake Michigan Friday evening...shifting winds to the northwest. Ahead of this front...the gradient will tighten with southerly gales over the northern portion of the lake by sunrise Friday morning and then across the rest of the lake by mid/late Friday morning. These gales will diminish just ahead of the cold front Friday evening. Wind speeds behind the front are expected to remain in the 30kt range...though some higher gusts are possible. Another large high will move from the Plains Saturday to the southeast U.S. Sunday and Sunday night. Another tight southerly gradient is expected next Monday with a chance of low end gales. cms
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&& .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Gale Watch...LMZ777-LMZ779...6 AM Friday to 9 PM Friday. Gale Watch...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM Friday to 6 PM Friday. && $$ 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 is the U.S. government's official web portal to all federal, state and local government web resources and services.