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Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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207 FXUS63 KILX 110814 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 314 AM CDT Sun Aug 11 2024 .KEY MESSAGES... - A weak disturbance will bring light showers to parts of central Illinois on Monday. - A stronger system will impact the region later in the week, triggering scattered showers and thunderstorms Wednesday night through Friday. The potential for severe weather and/or flash flooding will remain quite low. && .SHORT TERM...(Today through Monday) Issued at 314 AM CDT Sun Aug 11 2024 0730z/230am IR satellite imagery shows a large area of mid-level cloudiness extending from Missouri into south-central Illinois, mainly along/south of a Quincy...to Lincoln...to Paris line. Models have handled the cloud cover quite poorly: however, based on 00z NAM forecast soundings and latest satellite trends, think the clouds will persist across the southern half of the KILX CWA through daybreak...then gradually shift further southeast and dissipate by mid-morning. After that, FEW-SCT diurnal Cu will develop by peak heating and a few high/thin clouds will stream overhead as well. End result will be a partly sunny and mild day with afternoon highs in the upper 70s to around 80 degrees. A short-wave trough evident on latest water vapor imagery over Montana will cross the Rockies today, then approach from the NW late tonight into Monday. Thanks to subsidence from prevailing high pressure, the atmosphere will initially be quite dry. As a result, think light showers associated with the wave will remain along/west of a Galesburg to Springfield line through dawn Monday. As the wave arrives and the column gradually moistens from the top-down, scattered showers will spread E/SE across the KILX CWA later Monday morning. Most of the CAM guidance suggests the showers will primarily be focused south of the I-74 corridor...with the 3km NAM keeping the precip entirely S/SW of central Illinois. Have opted to reject the NAM and follow an HRRR/WRF-ARW/FV3 blend, which places high chance to likely PoPs south of I-74, but only 30-40 PoPs along/north of I-74. Any rainfall that occurs on Monday will be light, amounting to 0.25 or less. Thanks to extensive cloud cover and scattered showers, temperatures will be held down considerably...with much of the area only reaching the lower 70s. Barnes .LONG TERM...(Tuesday through Saturday) Issued at 314 AM CDT Sun Aug 11 2024 As has been seen with the past several model runs, it appears the primary baroclinic zone will remain well S/SW of central Illinois until the middle/end of the week. As such, think Tuesday will be a mild and dry day with highs in the upper 70s/lower 80s. As a stronger short-wave approaches from the Plains, the front will gradually lift northward by Wednesday. As a result, scattered showers will develop along/southwest of a Galesburg...to Effingham line late Tuesday night, then will spread across the remainder of the area on Wednesday. Despite the uptick in rain chances, think many locations will remain dry on Wednesday. As the wave nears and synoptic lift increases, rain chances will increase markedly Wednesday night through Friday. While it obviously will not rain the entire time, showers and thunderstorms will become more prevalent. Instability parameters remain modest, so the probability of severe weather will be low (less than 5%). In addition, while GFS precipitable water values increase to around 2 inches by Wednesday night/Thursday, the soil has dried out considerably since the previous rainfall...so excessive runoff is of minimal concern. In addition, the 12z Aug 10 LREF shows just a 20-25% of exceeding 1 inch of rainfall between 1am Thu and 1am Fri. Am therefore not anticipating any flooding concerns Wednesday night through Friday. After that, the strongest forcing and thus greatest rain chances will shift further east into the Ohio River Valley by Friday night into Saturday. Barnes && .AVIATION... (For the 06z TAFs through 06z Sunday Night) Issued at 1109 PM CDT Sat Aug 10 2024 Another VFR set of TAFS as high pressure over MO shifts east across central IL through Sunday. This will bring calm to light west to northwest winds and scattered mid to high level clouds. 25 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$