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Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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929 FXUS63 KILX 150047 AFDILX Area Forecast Discussion...Updated National Weather Service Lincoln IL 747 PM CDT Sun Jul 14 2024 .KEY MESSAGES... - Intense heat continues tomorrow, with heat indices of 100-110 degrees during the day. Not much relief is given overnight with lows in the mid to upper 70s. - Some relief from the heat comes Wednesday as a cold front pushes through central and southeastern Illinois over night Tuesday. The CPC shows a below normal trend on temperatures for the next 14 days. - Multiple MCS passages are forecast for the coming days before a brief break starting Wednesday. Some of these storms have the potential to be severe with damaging winds as the main risk. && .UPDATE... Issued at 746 PM CDT Sun Jul 14 2024 This evening, a broken line of thunderstorms has developed from near Rockford SW across the Quad Cities. Strong instability in excess of 3000 J/kg is in place ahead of this line of storms. 00Z ILX sounding showed a "loaded gun" setup with around 3000 J/kg MLCAPE and -68 J/kg MLCIN. Deep layer shear in the region is marginally sufficient (around 25-30kt) to support organized convection this evening and do anticipate storms to congeal into a more organized line over the next few hours. Cloud bearing flow and forward propagating corfidi vectors will generally steer these storms west-to-east across northern Illinois with some potential of clipping our far northern CWA where a severe thunderstorm watch is currently in effect. Damaging wind gusts will be the primary hazard with these storms. That said, veering LLJ this evening will help the southwestern end of the line back-build with upshear Corfidi vectors suggesting storms will propagate S/SW late this evening into portions of the area. Where this occurs, a heavy rain threat is possible due to the slow moving nature and training of storms. Latest HRRR suggests a few pockets of around or just in excess of 2 inches of rain is possible north of I-72. Deubelbeiss && .DISCUSSION... Issued at 214 PM CDT Sun Jul 14 2024 The MCS this morning skirted by the northern periphery of the CWA without incident. This won`t be the only round that threatens central Illinois. Currently, we are keeping a close eye on the MCV that is propagating through north-central Iowa. The HRRR and NAMNest depict the MCV and it`s reignited convection taking a southerly dip once it gets to Illinois, with the NAMNest being the most dramatic in its southern pull. The environment will have had time to recover from the morning convection, as surface heating occurs with the mostly clear skies, the moisture is far from gone (as we can feel the soupy airmass outside), and the MCV (and rebounding CAPE values) provides the needed lifting mechanism. By mid afternoon, SBCAPE values rise to ~3000 J/kg ahead of the CI, with very little to no cap. The main hazard as the next round moves through will be damaging, gusty winds. Tomorrow, the severe threat continues, but this time bigger and better than before. Another complex is expected to develop over Iowa by late morning and move eastward. Its track has it entering the northern CWA by late afternoon between 22-00z. As it does, the environment is primed. The cap is very little (~-20 J/kg), allowing the line to become surface based. SBCAPE values ahead of the line as it enters are 4000-5000 J/kg. The 0-6km bulk shear looks to be around 40-50 knots. SPC has areas along and north of I-74 outlooked for an Enhanced Risk (level 3 out 5). There is a 30% damaging wind risk with a 10% chance of wind gusts greater than 65 knots for areas along and north of I-72. Localized flash flooding is also in play for tomorrow as the area is already quite saturated and PWATs are 1.8-2 inches at the time of the passage. The heat won`t be taking a break tomorrow neither. Today the heat indices are expected to top out between 100 and 105 degrees. The dew points today and tomorrow will be in the upper 70s, getting very close to 80. The 12z.14 HREF shows a 60% chance of dewpoint exceeding 78 degrees tomorrow afternoon, ahead of the storm complex. Heat indices are forecast to top out near 110 degrees tomorrow (Monday). A cool down is expected starting Tuesday as a cold front is set to move through, wiping out the moisture. Beyond Tuesday, temperatures become slightly below normal for this time of year, giving us the well needed break from the soupy heat. Highs will be around the upper 70s to mid 80s from Wednesday into the end of the forecast period. There are some additional rain chances through early Thursday morning, then will be dry through Sunday. This break should give the area a chance to breathe after the multiple rounds of heavy rain recently. Copple && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 631 PM CDT Sun Jul 14 2024 Scattered storms upstream over eastern Iowa will be the focus for any activity spreading south into central Illinois later tonight. Confidence remains low in timing and placement, but the better chances for any storms will be at our northern 3 TAF sites (PIA, BMI, CMI). PROB30 groups are noted at each of these airfields between 04-10Z. South-southwest winds will become light overnight then turn breezy tomorrow afternoon. Mostly VFR conditions will be seen outside of storms, with another round of convection possible Monday evening. NMA && .ILX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT Monday for ILZ027>031-036>038- 040>057-061>063-066>068-071>073. && $$