Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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901 FXUS63 KILX 131525 AFDILX Area Forecast Discussion...Updated National Weather Service Lincoln IL 1025 AM CDT Mon May 13 2024 .KEY MESSAGES... - Showers and storms are expected (70-90% chance) mainly this afternoon through Tuesday afternoon. Coverage/potential of >1.0" rainfall is lowering. There is a 20-40% chance for more than an inch of rainfall in any one location. The widespread amounts now look to be in the 0.50-0.75 inch range. - Another system will bring rain to the area Thursday into Friday, with a 40-50% chance of rainfall amounts up to a half inch south of I-72. && .UPDATE... Issued at 1025 AM CDT Mon May 13 2024 The forecast is looking on track this morning as showers are beginning to move into central IL. The upper level low over KS will continue to approach from the WSW today, with the state experiencing broad warm air/moisture advection in the 850-700 mb layer currently. Expect shower and thunderstorm coverage to increase over the next several hours, peaking in the late afternoon/early evening hours. The NAM Nest has MLCAPE as high as 1500 J/kg this afternoon, but the HREF ensemble mean is closer to 500-1000 J/kg. Deep shear continues to look is rather weak today at 10-20 kts. Given these two key ingredients being rather low, severe storms are unlikely today. The SPC continues to have all of IL in general thunder today, with severe storms possible in the states further south and west. Knutsvig && .DISCUSSION... Issued at 325 AM CDT Mon May 13 2024 IR satellite loops are showing the upper level low over western Kansas and progressing slowly eastward. Synoptic scale lift is gradually increasing ahead of low as far east as north-central Missouri/south-central Iowa, where showers and a few storms are expanding in coverage. Southerly flow today will encourage modest low level moisture advection, to help overcome the dry sub-700mb airmass in place early this morning. Due to the dry antecedent air, the development of more widespread showers in central IL looks to begin this afternoon, when instability params indicate narrow MLCAPE as high as 1500 J/kg in the RAP soundings. Shear profiles remain marginal for strong storms, with 0-6km bulk shear at 25kts. However, a few supercells may develop per the elongation of straight hodographs with time this afternoon. Isolated hail and strong wind gusts could develop, but overall potential of severe weather is low. Given the patchy nature of the storm coverage, a few locations could see over 1.5" and others less than 0.5". The best chances of widespread showers looks to be this afternoon into evening, with that area shifting to south of I-72 on Tuesday afternoon. The consensus of ensemble guidance is still indicating a break in the rain mid-week in response to ridging at the surface and aloft across Illinois. That break will coincide with some cooler temps, with Wed morning lows in the upper 40s north of I-72. Showers and isolated storms return Thursday through Friday, with the highest potential (50-65% chance) Thursday afternoon into evening. Instability looks marginal with 500 J/kg MUCAPE amidst 0-6km shear up to 25kts. Potential of severe weather is quite low. A bright spot in the extended is for high temps to return to the lower 80s Saturday and Sunday, despite 20-30% chance for showers to bubble up each day. Shimon && .AVIATION... (For the 12z TAFs through 12z Tuesday Morning) Issued at 527 AM CDT Mon May 13 2024 VFR conditions will prevail this morning although ceilings will be steadily lowering as a storm system approaches. While a few showers are possible as early as 15Z, dry air in the lower levels will likely delay rain in most areas until the afternoon and evening. Main period for potential thunder appears during the mid to late afternoon. A few storms may linger into early evening from KPIA-KCMI, though this is less certain, and will not be mentioned at this time. A rapid expanse of lower ceilings is expected in the afternoon, and most sites should be MVFR by about 21-23Z. Ensemble guidance suggests ceilings may dip below 1,000 feet later this evening and linger through 12z as visibility drops to MVFR in light fog or drizzle. Shimon && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$