777 FXUS63 KILX 281545 AFDILX Area Forecast Discussion NATIONAL WEATHER SERVICE LINCOLN IL 1045 AM CDT Sun Sep 28 2014 .UPDATE... ISSUED AT 1045 AM CDT SUN SEP 28 2014 Forecast generally looks on track today and just slight modifications with sky cover today. A fair amount of sunshine expected again today with patches of mid/high clouds and few cumulus clouds this afternoon mainly from I-55 west and over the Wabash river valley. Warm highs in the low to mid 80s today and Monday with light winds. Patchy fog along the Wabash and IL rivers dissipated by 830 am leaving sunny to mostly sunny skies by mid/late morning. 1023 mb high pressure over lower MI and ridging westward into WI and central and eastern IA and northern IL will remain over the Great Lakes through monday and maintain fair wx with warm days. Dewpoints currently in the mid 50s to near 60F will slip a few degrees this afternoon so humidity levels will be fairly low again this afternoon. Temps currently in the low to mid 70s (except 68F at Lacon which had valley fog earlier this morning) will climb another 10 degrees into the low to mid 80s by mid afternoon. Weak 580 dm 500 mb low over far western IA near Nebraska border drift se into MO by sunset and keep its isolated convection west of IL. RAP/NAM curule shows few cumulus clouds this afternoon from I-55 west and over the Wabash river valley in southeast IL. Some patches of mid/high clouds drift over IL today but still a mostly sunny day expected. && .SHORT TERM...(Today) ISSUED AT 250 AM CDT SUN SEP 28 2014 A shallow layer of moisture below a subsidence inversion will allow some patchy ground fog to linger near river valleys early this morning (IL and Wabash rivers). Any fog should dissipate by 830 am. The 580dm 500mb low centered over NW Iowa will become an open wave and drift southeast across IL later today. That will bring scattered cirrus clouds with it, but sunshine should generally prevail across IL today. That will help high temps climb above all guidance numbers again today, as the dry low levels warm quickly. Temps should top out in the low to mid 80s this afternoon. Winds will remain light under a weak surface pressure gradient, with east to southeast winds of 5 to 8 mph again today. && .LONG TERM...(Tonight through Saturday) ISSUED AT 250 AM CDT SUN SEP 28 2014 Quiet weather expected for the start of the work week. Shortwave currently entering western Saskatchewan will be digging as it approaches Lake Superior, forming a closed low over Lake Huron by early Tuesday. This will drive a cold front southward, but general model consensus only brings it into northern Illinois before beginning to lift back north. 850 mb temperatures in the 11-13C range will keep our highs above normal, with some modest cooling on Tuesday as the front approaches. Have favored the warmer MAV MOS guidance during this period. Large upper low currently spinning over western Nevada still expected to swing northeast and weaken early this week, with a small closed low lifting through the Dakotas on Tuesday. This will help draw the previously mentioned front back north, before a stronger cold front moves in from the northwest. Still looks like Wednesday will largely be dry, before showers increase Wednesday night ahead of the front. Shear profiles increase nicely as the front gets closer on Thursday, with 0-6km bulk shear progged to reach 40-50 knots across much of the CWA Thursday afternoon per the ECMWF model, while the GFS is on the lower end of that range. Will need to continue watching the threat for some stronger storms Thursday afternoon and evening. Highest PoP's will be during the evening hours, with a quick decrease in rain from west to east after midnight following the passage of the front itself. Strong surge of cooler air to plunge into the Midwest on Friday in the wake of the front. Some model discrepancies exist at this range, as the GFS was more prominent on driving a surface low northeast along the front and amplifying as a significant upper low drops into Wisconsin. The ECMWF is continues with a smaller but strong open wave that races through the region on Friday. Both keep the coolest air to our north, but the GFS would be more of a threat with lingering wraparound showers. For PoP's, have continued to mention them in the 30-40% range, but currently think this would mainly be early in the morning. Temperature-wise, the GFS brings the 850 mb zero isotherm into central Illinois by late Friday and dipping below zero by early Saturday, while the ECMWF is already spreading warmer air back in by that point. With this discrepancy, the GFS would indicate highs only in the 50s on Saturday, while the ECMWF favors mid to upper 60s. Have favored more of a blend with Saturday as the coolest day, with highs mostly 60-65. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) ISSUED AT 637 AM CDT SUN SEP 28 2014 Fog has not developed near the terminal sites so far this morning, and any light fog over the first hour of the TAF period would be very brief if it develops. Overall, VFR conditions will prevail for the balance of the forecast period. A weak upper low passing over IL today will mainly bring an increase in high clouds. A few cumulus may form in the 4-5k ft layer as the 12z ILX sounding shows moisture in that layer. So any BKN ceilings would remain VFR. Surface winds will remain light east or northeast today and tonight with speeds of 3 to 7 kts. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...07 SHORT TERM...Shimon LONG TERM...Geelhart AVIATION...Shimon