118 FXUS63 KIWX 140522 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 122 AM EDT Wed Jul 14 2021 .SYNOPSIS... Issued at 724 PM EDT Tue Jul 13 2021 Mainly dry conditions are then expected overnight, although an isolated shower cannot be completely ruled out overnight. Dry and warm weather will be in store for Wednesday before higher chances of showers and thunderstorms return for Thursday afternoon into Friday. There is some potential of strong to severe storms and heavy rainfall Thursday afternoon into Thursday night. && .SHORT TERM...(This Evening through Wednesday) Issued at 355 PM EDT Tue Jul 13 2021 A slowly dampening upper level trough from the Great Lakes to the Ohio Valley will continue to be primary forcing mechanism for scattered to numerous showers and thunderstorms through early evening. MLCAPES on the order of 1000 J/kg and effective shear at or below 20 knots have favored multicell convection with some sporadic pockets of heavier rain and isolated wind gusts of 30+ mph. Heaviest rainfall over next few hours may materialize across north central Indiana/south central Lower Michigan where some enhanced low level convergence is expected with lake enhanced boundary in wake of weak sfc troughing. Eastward progression of upper forcing and gradual diminishment of diurnal instability should lessen shower/storm threat from west to east in the 22Z-01Z time period. May hold onto some slight chance shower PoPs overnight as water vapor depicts another upper level short wave working across Iowa this afternoon. Some very weak return low level moisture in advance of this feature could yield just enough elevated instability for a few showers overnight, but confidence is low. Upper level short ridging will shift across the western Great Lakes on Wednesday as next stronger upper level short wave approaches the Northern High Plains. Ramping up low level jet and stronger baroclinicity downstream of this feature is expected to result in widespread convection from Northern Plains to western WI/northwest Illinois later in the day Wednesday. Dry weather is expected locally on Wednesday, but may need to monitor for remnants of convective system to reach the southern Great Lakes Wednesday night before decaying. Corfidi vectors may tend to favor areas just north/northwest of local area for propagation, and with limited confidence will maintain just low chance PoPs across the north Wednesday night. Widespread severe weather is not expected Wednesday night, but some gusty winds are possible across southwest Lower Michigan into northwest Indiana with potential decaying convective line across the western Great Lakes. && .LONG TERM...(Wednesday Night through Tuesday) Issued at 355 PM EDT Tue Jul 13 2021 Thursday afternoon into Friday still appears to be shaping up as the most active period of the forecast. Upstream large scale upper trough should begin to acquire more of a positive tilt as it encounters some blocking from negative upper height anomaly dropping southeast out of Hudson Bay. Strengthening low/mid level flow downstream of the Upper Midwest trough axis will bring renewed impressive deep moisture profiles back into the area with PWATs on the order of 1.9+ inches. The greatest uncertainty in this forecast lies with mesoscale details and positioning of any leftover outflow boundaries from upstream overnight convective complex. Given strengthening advective fields with the positively tilted upper trough, will continue to hedge this forecast to good deal of destablization Thursday afternoon into Thursday evening. Shear profiles will begin the day marginal but will increase in the afternoon and evening as flow increases. All of forecast area has been placed in Marginal Risk for Thursday/Thursday night, although potential does appear to exist for increasing severe probabilities over next several forecast cycle particularly across northwest half of the forecast area from west central Indiana into south central Lower Michigan where shear/instability overlap appears most favorable at this far forecast distance. Forecast confidence in details dwindles Friday and Saturday as cold front pushes southward, and uncertainties if any composite outflow boundary becomes the effective front. The setup appears to favor a sharp NW to SE gradient in instability Friday afternoon with approach of lagging mid/upper level trough, but exactly where this gradient sets up is of low confidence. In addition to severe potential Thu/Thu night/possibly into Friday, will have to watch for locally heavy rainfall amounts in this setup due to positively tilted nature of upper trough, weak propagation vectors via strengthening low level jet, and abundant low level moisture. Not much change to previous forecast post-Friday as building mid/upper level ridging across central CONUS should keep precip chances increasingly suppressed south of the area as we progress later in the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday Night) Issued at 122 AM EDT Wed Jul 14 2021 Primarily VFR conditions expected through the period though some brief MVFR may be possible at times. Some shallow BR possible this morning but approaching high clouds will likely limit duration and impact. Confidence is low and impact would likely be minor (5SM) so will hold off for now. Also expect a healthy diurnal cu field that may briefly hover around 3 kft during the late morning but will quickly climb to around 4 kft as mixing increases. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Marsili/Roller SHORT TERM...Marsili LONG TERM...Marsili AVIATION...AGD 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