Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/11/19

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
700 PM CDT Wed Jul 10 2019 .SHORT TERM... 1237 PM CDT Through tonight... Thunderstorm chances continue to be the main forecast question, though heat indices around 100 degrees this afternoon may be causing the bigger impacts. Regarding convective trends, most of the latest CAMs have at best some spotty development for the rest of the day into the evening, with the southeast portion of the forecast area most favored. Cumulus development is very sparse across our western half and just upstream of the area so far. This is probably related to the nose of warm air just above 800mb being seen in late morning AMDAR data and reflected in the latest RAP soundings. The RAP shows this cap eroding somewhat but not completely this afternoon, so have held onto a slight chance of storms mainly across our southeast where the cumulus field is more robust and the passing cold front will coincide with the best diurnal support. Expect that anything that does manage to develop this afternoon to wane during the evening and then dry conditions to prevail into tomorrow morning. With dewpoints in the 60s by morning rather than lower 70s like this morning, low temperatures tonight behind the cold front should also be a few degrees cooler than this morning. Lenning && .LONG TERM... 218 PM CDT Thursday through Wednesday... A relatively quiet period is setting up for the long term forecast period. The upper level pattern is transitioning to a broad low amplitude long wave pattern with an upper high parked over the Southern Rockies/Four Corners region and the western extent of the Bermuda high staying east of the Florida Peninsula. Meanwhile, a series of upper troughs will dig through the Eastern Great Lakes and southeastern Canada. Broad wnwly flow aloft will persist from Thursday into early next week. Weak shortwave energy dropping through the wnwly flow aloft may bring a few chances for some showers and thunderstorms, but with the main upper forcing shunted north of the Wisconsin border, and pcpn chances will be low, and likely be glancing the far nrn portions of the CWA. For Thursday and through the weekend, sfc high pressure will also be firmly established across the region, leading to warm, but less humid conditions. By Friday night, a weak cold front from an associated low over northern Ontario will sag southward across the Upper Mississippi River Valley. This weak front may skirt the northern extent of the sfc high pressure. Latest guidance still suggests that the front will stall over or just north of the CWA late Friday night into Saturday, supporting at least small chances of convective activity during this time, mainly for the northern portions of the CWA. Through the weekend and into early next week, a weakness in the upper level flow between the upper ridge over the swrn CONUS and the Bermuda high east of FL may allow a potential tropical system to sneak north into the Lower Mississippi Valley. While there is still considerable uncertainty as to how this system will develop and where it may track, it will need to be watched over the next few days to see if any moisture associated with this system can get into, at least, the southeastern portions of the CWA by the middle of next week. && .AVIATION... For the 00Z TAFs... 700 PM...Forecast concerns include... Isolated thunderstorms this evening...southeast of the terminals. Wind shift to northeast Thursday morning. Mvfr cigs Thursday morning. A weak cool front is moving across the area currently and isolated thunderstorms will be possible southeast of the terminals for the next few hours. Westerly winds will turn northwesterly this evening with gusts into the lower 20kt range possible through sunset. Winds will continue to turn northerly by daybreak and will become northeast Thursday morning. Confidence on timing is only medium and its possible that winds will shift northeast earlier than currently advertised in this forecast. Gusts into the mid/upper teen kt range will be possible Thursday afternoon diminishing Thursday evening. Much of the guidance is suggesting mvfr cigs will develop after sunrise across the area with cigs near 1kft across much of northwest IL. Followed these trends and introduced mvfr cigs with this forecast but confidence on specific heights is low. Cigs should begin to lift by late morning with scattering expected in the afternoon. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...Beach Hazards Statement...INZ001-INZ002...2 PM Thursday to 4 AM Friday. LM...Small Craft Advisory...LMZ743-LMZ744-LMZ745...2 PM Thursday to 4 AM 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