Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/03/21

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
633 PM CDT Mon Aug 2 2021 .SHORT TERM... 156 PM CDT Through Tuesday night... Spotty light sprinkles/showers will continue this afternoon within an expansive region of diurnally-enhanced cumulus north and west of I-55/57 and east of I-39. Latest VAPOR AMDAR soundings out of MDW/ORD suggest that, when accounting for dewpoints in the upper 50s, MLCAPE values around 250-300 J/kg are being realized. Stout warming just under 600 mb will continue to limit vertical growth of any convective cores today, even with the arrival of an upstream shortwave. We`ll continue to indicate some low shower and sprinkle chances through around sunset today. With skies expected to clear this evening and overnight, the dry airmass in place, combined with light winds will allow temperatures to drop back into the low to mid 50s away from Chicago once again, with a smattering of near 50 degree readings not out of the question in our typical cool/outlying locales. Suppose some spotty, very shallow fog is possible where temperatures settle to the dewpoint overnight. Broad cyclonic flow continues aloft tomorrow with an altogether similar look to things compared to today, with a secondary vort lobe slated to drop into southern Wisconsin through the afternoon. Forecast soundings look a bit less supportive of precipitation tomorrow, however, with slight boundary layer drying, combined with the warm layer/subsidence inversion descending to around 700 mb or so. As a result, will continue with a precipitation-free forecast tomorrow under another healthy late-morning and afternoon Cu field. High temperatures should be a degree a few degrees warmer than today. Carlaw && .LONG TERM... 229 PM CDT Wednesday through Monday... An upper trough extending from the Great Lakes to northern Florida will weaken and drift eastward Wednesday while weak high pressure will be in place at the surface. This will yield another pleasant day with highs similar to or a couple degrees warmer than Tuesday. A southeasterly lake breeze will develop keeping IL lakeshore areas several degrees cooler. Dry weather persists for Thursday but an upper shortwave will approach Thursday night and cross the area Friday morning. There will not be a great opportunity for much moisture return but there will be enough support for low chances for showers/thunderstorms late Thursday night through Friday morning. A stronger trough pushing into the Pacific Northwest will force upper ridging eastward across the plains and Mississippi River Valley into Saturday while also breaking it down. Stronger southwesterly low level flow sets up bringing a warmer and more humid airmass into the area. Expect highs to warm into the upper 80s to around 90 Saturday over the weekend and into Monday. Low to mid 70s dewpoints will bring heat index values to around 100 Sunday and Monday. Shower/thunderstorm chances are more ambiguous at this point and should be focused to the north overall, but the warm and unstable airmass would be supportive of development with any ripple in the newly established zonal flow. MDB && .AVIATION... For the 00Z TAFs... Aviation Forecast Concerns: * Easterly lake breeze winds diminishing and veering southeast this evening. Becoming light with westerly land breeze component overnight, then easterly lake breeze again Tuesday afternoon. Weak surface pressure gradient was in place across the region late this afternoon/early evening in the vicinity of high pressure ridge across the Midwest. Combination of light/variable winds, lake breeze and some isolated shower outflow/differential heating has made for a messy...but light...wind field. Overall trend should be fore easterly lake breeze winds across the Chicago terminals to weaken and veer southeast this evening, potentially becoming light/variable for a time before taking on a light westerly land breeze component overnight. VFR ceilings in the 6-10 kft range should also scatter out during the night with the loss of diurnal heating and the passage of a mid-level wave this evening. Similar weather expected Tuesday, with diurnal increase in VFR cumulus and an easterly lake breeze wind shift for the Chicago metro terminals in the early afternoon hours. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at: