731 FXUS63 KILX 232057 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 357 PM CDT Fri Apr 23 2021 .SYNOPSIS... Issued at 255 PM CDT Fri Apr 23 2021 Rainfall will develop and become more widespread tonight across the region. Amounts have trended downward, but much of the region will receive about a quarter-inch of rainfall. Rain will end from west to east Saturday afternoon and evening, and Sunday looks like a pleasant day with seasonable conditions returning for the region. An impressive warming trend arrives early next week, and a more active stretch of weather appears likely by the middle of next week. && .SHORT TERM...(This evening through Saturday) ISSUED AT 255 PM CDT Fri Apr 23 2021 Clouds will continue to increase in coverage this evening as synoptic-scale ascent becomes enhanced over the region ahead of an upper- level trough lifting into the Southern Plains. Low-level moisture return continues to advect northward overtop a baroclinic zone draped across the Deep South. Still, model soundings suggest it will take several more hours before the lower troposphere become sufficiently saturated to support widespread showers. QPF has continued to trend downward over the last 12 hours, with most of the outlook area now expected to receive about one-quarter inch of rainfall. This downward trend in QPF makes sense given modestly saturated forecast parcels and the fact that the better synoptic forcing associated with the main upper shortwave remains well south of the region overnight. Still, there could be some thermally-induced forcing on the northwest side of the surface frontal system. A quick glance at 2-D frontogenesis plots reveals some enhancements along and north of the I-72 corridor Saturday morning, mainly in the 800-750mb layer. There, a narrow stripe of locally higher rainfall amounts, perhaps up to 0.75", will be possible. Rainfall will end from west to east between Saturday afternoon and evening as mid-level moisture pulls away from the region and subsidence begins to work in behind the departing upper-level shortwave. Temperatures tonight into Saturday morning will remain mild with lows near 50 degrees. Afternoon highs on Saturday will warm into the upper 50s for much of the outlook area, except west of the Illinois River Valley where low 60s will be possible due to some late afternoon sunshine. Lows Saturday night will be seasonably cool with temps cooling near 40 degrees. && .LONG TERM...(Sunday through Friday) ISSUED AT 255 PM CDT Fri Apr 23 2021 A warming trend will commence Sunday as skies become mostly clear with weak surface high pressure building across the Great Lakes region below increasing mid-level heights. Seasonable temperatures are expected with afternoon highs warming into the middle 60s. Nighttime temperatures will remain mild Sunday evening as surface high pressure builds into the Appalachians and low-level winds veer southerly and become breezy; expect lows in the upper 40s, especially across our western outlook area. Breezy and much warmer conditions are expected Monday and Tuesday as a deep upper-level trough moves onshore the West Coast. Mid- level height rises will continue as deep southwest flow advects warmer low- level air into the region from the Southern Plains. Forecast soundings reveal 850mb temps in the 15-17C range for both Monday and Tuesday afternoon, which is near the climatological max for this time of year. This air mass likely will not break records, but it will be enough to send afternoon temperatures surging into the middle 80s each day, with overnight lows in the lower 60s. This will also be the most humid air mass so far this year with surface dewpoints progged in the middle-to- upper 50s. As a final note for Monday and Tuesday, gusty synoptic winds will be in place as the surface pressure gradient tightens ahead of a frontal system. Frequent gusts near 35 mph will be likely each day, and some locally higher gusts will be possible if slightly deeper mixing occurs. The Wednesday through Friday period continues to look more active across the mid-Mississippi Valley with the latest suite of ensemble guidance coming into better alignment. CIPS analogs continue to hint at multi-day severe weather potential across central Illinois, while NAEFs exhibits PW values exceeding the 99th percentile. With the latest guidance showing a slower progression of the mid-week upper-level wave and an elongated baroclinic zone draped across the region, a flash flooding signal looks increasingly likely. It is important to note, however, that timing and placement of these threats is still uncertain. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1207 PM CDT Fri Apr 23 2021 Mid-level overcast with VFR ceilings through 00z, then cigs gradually deteriorate thereafter with the arrival of an inverted surface trough and light rain. Regional aerodromes will sit between MVFR/IFR for the remainder of the TAF period as weak surface convergence and sufficient low-level moisture help keep lower ceilings in place. Surface winds sustained between 10-15 kts this afternoon with occasional gusts to 20 kts, then diminishing and gradually backing toward the east overnight. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MJA SHORT TERM...MJA LONG TERM...MJA AVIATION...MJA