Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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885 FXUS63 KILX 231945 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 245 PM CDT Thu May 23 2024 .KEY MESSAGES... - There is a slight risk (level 2 of 5) for severe weather for all of central and southeastern Illinois for tomorrow. These storms could produce damaging winds and large hail. - There is a 80-100% chance of thunderstorms on Sunday. These storms have the potential to be severe, with a 15-30% chance for severe weather that day. && .DISCUSSION... Issued at 245 PM CDT Thu May 23 2024 There are a few rounds of low pressure systems and it associated frontal passages over the coming days. The first of which arrives tomorrow morning. A cold front is expected to move through central and southeastern Illinois late morning/early afternoon tomorrow, bringing along severe weather potential. A brief surface high pressure will set up for Saturday before the next low pressure system passes to the north/northwest of the CWA Sunday. This low will bring its associated cold front through the area in the afternoon to evening hours. This system on Sunday will have the greatest risk for severe weather. This forecast cycle will put a lot of focus on what is coming tomorrow. The models are being difficult and not agreeing on timing or how the storms will move through the CWA. They do agree on storm type, however. It will move through as a QLCS but whether it will be a broken line or not is up for debate. The HRRR and NAM 3km differ in timing somewhat, with the NAM 3km being a bit slower. The line will enter our western border between 15z and 17z. The HRRR has the QLCS moving through as solid line that goes across the entire CWA. Whereas the NAM 3km shows a broken line. The northern portion of the line propagates across the CWA (north of I-72), with the southern portion developing slightly later as the first line exits the state around 21z. This second line stretches further south along our entire CWA. The HRRR shows the activity exiting Illinois around 23z but the NAM 3km shows it lingering longer to around 4z. The chances of redevelopment behind the front is basically non existant at this time. Temperatures tomorrow get up into the low to mid 80s. In more mesoscale news, the storms should be surface based. The HREF 12z run shows a 50-60% chance of greater than 3000 J/kg of SBCAPE ahead of the front. There is a brief cap in the morning that quickly erodes by mid morning. DCAPE values associated with the system shows 1000- 1500 J/kg. There appears to be an inverted V signature on the 18z HRRR soundings ahead of the front. The hazards most likely to impact central and southeast Illinois with this round of severe weather is primarily hail and severe wind. The wind threat is the highest risk for tomorrow, which the inverted V soundings and high DCAPE values support. PWAT values max out around 2 inches but the fast moving nature and training isn`t expected will limit the flooding threat. Localized higher amounts could occur. Saturday a high pressure settles of the area briefly, providing us a short break before the next round of severe weather on Sunday. Sunday another low pressure system is progged to move just north/northwest of the CWA, bringing the next chance for severe weather. There is a 15-30% chance for severe weather, with the greatest risk down in southeastern Illinois. Timing of the system is sort of uncertain currently but it looks to move through Sunday morning into the afternoon in a linear storm mode. This round is looking more impressive than the system expected tomorrow afternoon. Memorial Day, Monday, looks to be windy and pretty dry. A few pop up showers aren`t completely ruled out but basically dry. Stay tuned as the holiday weekend gets closer and this first system gets out of the picture for more detailed information. Copple && .AVIATION... (For the 18z TAFs through 18z Friday Afternoon) Issued at 1250 PM CDT Thu May 23 2024 VFR conditions will prevail across the central IL airport through Friday morning, and generally dry conditions expected. SE winds of 5-10 kts with a few gusts 15-20 kts into mid afternoon will be fairly light tonight. Winds then veer south and increase to 12-17 kts with gusts 20-25 kts after 15Z/10 am Fri. Scattered to broken cumulus clouds with bases of 4-7k ft will occur along I-72 this afternoon. Fair skies are expected tonight across the central IL airports with mid/high clouds increasing during Friday morning. Patchy fog possible late tonight though coverage appears too limited to mention in TAFs. A broken line of convection will track eastward toward the IL River valley and by near PIA by 18Z/1 pm Fri and VCTS added to PIA after 17Z. Main line of convection to move eastward over central IL airport Friday afternoon just after this TAF period and likely have stronger impact on PIA and BMI. 07 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$