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Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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818 FXUS63 KILX 181716 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1216 PM CDT Thu Jul 18 2024 .KEY MESSAGES... - Seasonably cool and dry into the weekend, with high temperatures in the upper 70s to low 80s which is 5 to 10 degrees below normal. - Precip chances return throughout next week, with a 20-50% chance each day. && .UPDATE... Issued at 1013 AM CDT Thu Jul 18 2024 High pressure and associated dry air continue to work their way into central IL, and will result in dry weather and cooler than normal temperatures today. A band of cloud cover has developed over Lake Michigan drifting SSW-ward into central IL, creating a broad band of scattered cloud cover mainly east of I-55, but diurnally forced cumulus has already begun to develop as well. Highs today in the upper 70s look on track. Updates this morning have been to increase cloud cover slightly, but overall the forecast is on track for today. 37 && .DISCUSSION... Issued at 201 AM CDT Thu Jul 18 2024 An expansive 1024-mb sfc high pressure was centered over Minnesota early Thursday morning, and this sfc high will slowly shift southeast becoming centered over Illinois by Friday morning. With this broad sfc high pressure in control, conditions will be seasonably cool and dry through the weekend. Today will be the coolest day of the stretch, with highs peaking in the upper 70s, then gradual warming occurs through the weekend as highs return to the low 80s, which is still below normal. By the weekend, guidance continues to depict a slow-moving, closed upper low developing west of the area on Saturday. This upper low meanders about for a few days, with its associated forcing progged to stay far enough west that the ILX CWA stays dry through the weekend. Eventually though, that forcing shifts east and provides a chance for showers/storms (20-50% chance, highest south of I-70) early next week (Mon-Wed). The forecast PWAT values have trended higher, and are now progged to be near seasonable values (1.5") on Mon. Both PWAT and instability values gradually trend higher each day next week, but the instability values are still seasonably low, generally near or below 1000 J/kg each day Mon-Wed. Deep layer shear also looks weak, with 500 mb flow around or under 20 knots, and thus severe storms continue to appear unlikely. Given the increase in PWAT values and the potential for light flow in the cloud bearing layer, slow storm motions (less than 15 mph) could lead to localized instances of heavy rainfall. At any one location, the odds of heavy rainfall are low, with only a 10-20% chance of exceeding 1" of rain through next Thurs AM. Around mid-week, a stronger shortwave digs towards the upper Midwest, resulting in continued forcing for precip Wed night- Thurs. With continued upper troughing over the Great Lakes, temps are favored to stay near or below normal into the latter half of next week. Erwin && .AVIATION... (For the 18z TAFs through 18z Friday Afternoon) Issued at 1216 PM CDT Thu Jul 18 2024 Extensive diurnal cloud cover this afternoon should result in SCT-BKN coverage with cigs generally over 3000 ft AGL, however some isolated MVFR cigs can`t be ruled out. Cloud cover should dissipate this evening, then return after 16Z, although generally not as much coverage and slightly higher. Winds NE 6-10 kts, becoming light and variable after 01Z, then returning 4-8 kts by 16Z. 37 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$