742 FXUS63 KILX 020756 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 256 AM CDT Wed Apr 2 2014 .DISCUSSION... ISSUED 255 AM CDT Wed Apr 2 2014 A busy period on tap through Friday, with excessive rainfall amounts and severe weather a concern. SHORT TERM...Today through Friday: Large upper low currently located near San Francisco will be swinging eastward across the Rockies tonight and into the central Plains on Thursday. Showers and isolated thunderstorms have been moving through the central third of the CWA over the last several hours, in the narrow baroclinic zone along the 850 mb warm front. Dry air sampled by the 00Z upper air sounding was still in place over the northern CWA and has kept the rain at bay up there, but this will erode later this morning. Much of the rain will be across the northern half of the CWA by afternoon, with a period of more scattered showers/storms south of I-70 where the surface warm front will be moving in from the south this afternoon. The front is still progged to lift northward to around I-72 late tonight, then slowly creep northward Thursday before the surface and upper low track northeast into eastern Iowa and drag the front fully through the forecast area. Showers/storms should be on the increase again tonight as mid level lapse rates steepen. Precipitable water values increase to 1.4 to 1.5 inches by late tonight and will remain very high through Thursday evening. Forecast rainfall for this event through early Friday on the order of 3 to 4 inches over a large area of central Illinois, with 2 to 3 inches from about Rushville to Bloomington northward. While this is not expected to fall fast enough to cause flash flooding, there is still a significant concern for areal and river flooding to develop, thus a flood watch is being issued for a large part of central and southeast Illinois. Some more sustained breaks in the showers/storms expected for a time on Thursday as the CWA gets more fully in the warm sector. Still think that 70-75 degrees will be common from I-72 southward for highs, which will allow CAPE's to rise to around 1800 J/kg during the afternoon and evening. Decent 0-6km bulk shear of around 35-40 knots will contribute to the severe weather potential, with a large part of the forecast area in the SPC Day2 outlook's 30% "hatched area" which indicates potential for more significant severe conditions. Main severe weather threat will be in the evening, perhaps lingering across eastern Illinois after midnight as a squall line pushes through. Much of the precipitation will end on Friday, but some wraparound showers are possible into the afternoon across the north. Freezing level dips to around 1500 feet, so cannot rule out a couple of snowflakes mixing in, but will keep the forecast as all rain for now. LONG TERM...Saturday through Tuesday: Main concern in the long term remains with the storm system that will form near the Gulf coast late this weekend, as a large upper trough pushes through the central U.S. The ECMWF has continued its trend of stronger, faster and further northwest than the GFS. This solution would spread rain as far northwest as I-55 by early Monday, while the GFS precipitation shield largely misses us. Have generally kept PoP's in the 30-40% range due to the potential for some light showers with the trough itself as it moves through Illinois. Geelhart && .AVIATION... ISSUED 1115 PM CDT Tue Apr 1 2014 Not much change from previous discussion. The main challenge will be how far north the rain gets overnight and its affect on cigs and vsbys by morning. Band of rain continues to edge slowly north late this evening and expect this trend to continue overnight with most areas seeing some light QPF. Showers and TSRA were developing over parts of NW Missouri late this evening and expect this batch of precip to make its way into west central Illinois by morning and encompass most of the area by afternoon, which looks to be enough to saturate the lower levels of the atmosphere enough to bring cigs to MVFR category which looks to last thru most of tomorrow night with periods of rain and isold TSRA. Surface winds will be mainly from an east to northeast direction with speeds ranging from 7 to 12 kts tonight and from 10 to 15 kts on Wed. Smith && .HYDROLOGY... ISSUED 255 AM CDT Wed Apr 2 2014 QPF values of 3 to 4 inches forecast for a large part of central and southeast Illinois through early Friday. While this will be over an extended period limiting the flash flood potential, there will still be areas of flooding as the ground becomes very saturated. Significant river rises will be on tap, with flooding likely to develop along the Illinois and Sangamon Rivers. Ensemble hydrographs from NCRFC using 50th percentile precipitation showing sites reaching minor flood stage by Friday or Saturday. Similar guidance from OHRFC projecting flooding also along portions of the Little Wabash, Embarras and Wabash Rivers. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH from this evening through early Friday morning for ILZ042>057-061>063-066>068-071>073. && $$