Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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365 FXUS63 KILX 240132 AFDILX Area Forecast Discussion...Updated National Weather Service Lincoln IL 832 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. && .UPDATE... Issued at 832 PM CDT Thu May 23 2024 No significant changes needed this evening. An approaching low pressure system will lift a warm front slowly northward through the area overnight, increasing low level moisture and cloud cover. Precipitation will likely hold off until late morning (West of I-55) to afternoon (east of I-55). Lows in the lower to mid 60s look on track, considering at least light winds, cloud cover, and increasing dewpoints. 37 && .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 00z TAFs through 00z Friday Evening) Issued at 646 PM CDT Thu May 23 2024 A line of thunderstorms or perhaps a few distinct shorter thunderstorm lines look on track to affect the central IL terminals Friday afternoon. However, timing and location of these lines is still highly uncertain. At this point, have included VCTS in all TAFs starting 17Z-20Z, but will hone in on more precise timing of any thunderstorms at individual terminals with subsequent TAF issuances as predictability improves. For now, have kept all conditions VFR as MVFR or worse cigs/vsbys will likely be fairly short-lived, but any thunderstorms could produce brief lowered flight categories. Winds S-SE 5-10 kts overnight, becoming S around 15 kts with gusts 20-25 kts by 15Z-18Z. 37 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$