Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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079 FXUS63 KILX 161046 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 546 AM CDT Thu May 16 2024 .KEY MESSAGES... - Severe weather potential remains low both Thursday and Friday, with the probability of greater than one inch of rainfall in the 10-20% range south of I-70. - Prepare for warming temperatures this weekend, with a 40-80% chance of high temperatures above 85 F. The greatest chances for temperatures in excess of 85 F are south of I-70. && .DISCUSSION... Issued at 322 AM CDT Thu May 16 2024 With light winds and some areas of clear sky apparent on satellite particularly in eastern Illinois in an environment with minimal dew point depressions, we`ve seen some areas of fog start to develop. Visibility has locally been reported as low as a half mile. With clouds gradually moving in from the west, we expect any dense fog to remain transitory and localized. Look for most of the fog to dissipate by shortly after sunrise. Radar shows the first shower activity moving out of eastern Missouri in an environment with a few hundred J/kg of MUCAPE but minimal shear. Shower and thunderstorm activity is forecast to increase from the southwest through the morning ahead of an eastward-advancing thunderstorm complex coming out of southeastern Kansas. HREF probabilities depict shower and storm initiation west of I-55 in the 10-11 am time range, with storms moving east/northeastward through the late morning and afternoon. The same HREF probabilities show activity backing off across southern/southwestern portions of the ILX CWA in the 3-5 pm range, with showers ending from southwest to northeast. A few members keep convective activity going east of I-55 well into the evening. Though MUCAPEs reach around 1000 J/kg, shear is forecast to be on the low side this afternoon/evening except perhaps locally south of I-70 so severe weather probabilities are low. Rainfall will be highly variable, with many areas receiving little or none and a few receiving an inch or more. Model forecasts have trended a bit southward with the low track for Friday, and portions of the ILX CWA receiving precip Friday may be limited. A weak boundary with little temperature or moisture contrast across it is depicted in model forecasts, lifting northward on Friday to various degrees. Precip chances are greatest south of I-70, with a noticeable drop-off from southeast to northwest. In reality many north of I-72 may not receive any rain at all on Friday, but felt it wise to include some precip chances in the afternoon as some ensemble members show storm initiation occurring along the convergence boundary and the position is uncertain. With enough members such as the deterministic 00z GFS showing a slower wave on Saturday, keeping precip going particularly in the southeast, 20-40% precip chances persist though precip amounts are not forecast to be much. Behind the low, a short wave ridge pushes in and temperatures begin to warm. Starting on Sunday and continuing through Tuesday, the probability of high temperatures greater than 85 F goes up into the 40-80% range. The greatest probability for these very warm temperatures will be south of I-70. In addition to the warm temperatures, severe storm ingredients will return with increasing instability, increasing shear in southwest flow, and multiple waves forecast to move through the flow. Though it`s difficult to time or place the individual waves at this point, the most likely date for active weather in the vicinity of central Illinois is Tuesday. AAT && .AVIATION... (For the 12z TAFs through 12z Friday Morning) Issued at 546 AM CDT Thu May 16 2024 Plan for scattered showers and thunderstorms to move in from the southwest later this morning, developing near KSPI first around 16-17z and moving north/east from there. Conditions will likely remain VFR through the daytime hours with low VFR ceilings developing in association with the showers and thunderstorms, aside from perhaps MVFR to IFR visibility should a moderate to heavy rain shower move directly over a terminal. Overnight, look for MVFR to IFR ceilings and visibilities developing especially near and north of a line from KTAZ-KPRG. AAT && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$