173 FXUS63 KILX 182358 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 658 PM CDT Wed Sep 18 2019 .SYNOPSIS... Issued at 201 PM CDT Wed Sep 18 2019 High pressure over the region will continue to provide fair weather conditions to central Illinois through the remainder of the work week. Heavy rain appears likely over the weekend as a cold front sweeps across the region and combines with moisture from the remnants of tropical depression Imelda currently over Texas. && .SHORT TERM...(This evening through Thursday) ISSUED AT 201 PM CDT Wed Sep 18 2019 Fair weather will continue through the remainder of the week as central Illinois remains on the western periphery of an expansive ridge that extends from New England across the Midwest. Water vapor imagery reveals an upper low lifting northeast from north Dakota to the Canadian Prairies. This occluded system has a cold front in place across Iowa and Nebraska. This cold front will weaken and dissipate as it slowly shifts east towards the ridge and as the upper low lifts northeast away from the surface features. Precip associated with the front may reach the Mississippi River but for now does not appear it will impact central Illinois. Temperatures remain warm for mid September. Overnight lows should remain in the low 60s and temperatures Thursday will warm back into the mid to upper 80s. .LONG TERM...(Thursday night through Wednesday) ISSUED AT 201 PM CDT Wed Sep 18 2019 Main forecast concern will be the heavy rain potential over the weekend. This afternoon, water vapor imagery reveals a deep trough digging onshore over the west coast which is progged to shift east across the central Great Plains late in the week and over the weekend. Meanwhile, increasing southwest flow in advance of this system will help to spread moisture from the remnants of Imelda north into portions of the Midwest. Models suggest PWat values increase to around 1.50-1.75 inches by Friday, which would be around the 90th percentile per recorded soundings from ILX. It remains uncertain how high those values rise over the weekend, but the GFS at least brings in values of around 2.00 inches which would be near daily records. Bottom line is that tropical moisture advecting over the region this weekend may bring copious amounts of precip to central Illinois. GEFS plumes show a number of members clustered between 1 and 3 inches with a few locally higher members. For now it appears precip will peak in intensity starting Saturday night, as warm moist advection maximizes over the region, into Sunday night as the surface cold front associated with the aforementioned upper trough finally pushes across the area. While soundings are quite moist, the tropical environment does not have much instability, which may limit lightning activity to more isolated to widely scattered embedded nature. Cold front is progged to lay out south of the forecast area along the Ohio Valley early through the middle of next week, eventually lifting back north across the plains. Meanwhile, a transient high will shift east across the Great Lakes through this time. Will maintain some PoPs associated with the stalled boundary each day next week, increasing from the southwest Tuesday and Wednesday as the next wave arrives. Temperatures, which will continue to run very warm ahead of the front Friday and Saturday with highs in the 80s, but will moderate back closer to seasonal norms behind the front with highs in the 70s next Monday through Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 658 PM CDT Wed Sep 18 2019 VFR conditions can be expected across all of central and eastern IL through the next 24 hour TAF period. An instability axis along and just west of the MS River has resulted in a few thunderstorms from central IA to just south of Quincy this evening. These mainly diurnal storms are not expected to make it too far into west central IL as they encounter a drier, easterly flow. Only some higher level cirrus blow off clouds from the thunderstorms will survive the trip into central IL. Overnight and into Thursday, a mainly clear sky can be expected with scattered high clouds and a light southeast wind. The exception will be along and west of the IL River - including KPIA, where a broken deck of altocumulus/cumuls will move in from the WNW. Some of the models are trying to show some convection moving into west central IL from the NW. However, this looks suspect as the southeast flow keeps the best low level moisture to the west of the area. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...Deubelbeiss SHORT TERM...Deubelbeiss LONG TERM...Deubelbeiss AVIATION...Miller