Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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445 FXUS63 KILX 131619 AFDILX Area Forecast Discussion...Updated National Weather Service Lincoln IL 1119 AM CDT Thu Jun 13 2024 .KEY MESSAGES... - A prolonged period of unseasonably hot weather will continue through next week. Temperatures will range from the middle 80s to middle 90s, with the heat really ramping up Sunday into early next week as heat indices approach 100. - Storm chances (50-80%) return late this afternoon into tonight. Scattered to numerous severe storms are possible with the primary hazards being damaging wind gusts in excess of 75 mph, large hail up to baseball size, and heavy rainfall. && .UPDATE... Issued at 1119 AM CDT Thu Jun 13 2024 Frontal system is still over WI and IA, but will drop south into northern IL this afternoon. Storms are still expected to develop along the front and move southeast into the CWA late this afternoon and continue into this evening. Timing could be a little slower than current forecast, but only in the eastern parts of the CWA. Very warm temps are still expected this afternoon with upper 60 dwpts, resulting in HIs in the 90s across most of the area, with near 100 in the far western parts of the CWA. Overall, current forecast looks fine, so no update was sent out. Auten && .DISCUSSION... Issued at 346 AM CDT Thu Jun 13 2024 An upper shortwave trough is working into the Northern Plains states early this morning with a 70-90 kt mid-level jet set to push the wave into the Great Lakes Region later today. A deepening surface low is working across Ontario/Quebec with a cold front stretched southward from northern Michigan southwestward into South Dakota as of 3 am. Decaying convection tied to the front is ongoing over central Wisconsin and eastern Iowa, and will continue to drop south this morning, bringing a small chance for a few isolated showers or a rumble of thunder west of the Illinois River around sunrise. The cold front will continue to sink south today, approaching the area late this afternoon and becoming the focus for thunderstorm development by late this afternoon or early evening. Strong heating ahead of the front will send temperatures into the upper 80s to low 90s with gulf originated moisture bringing dewpoints into the upper 60s to low 70s. Moderate to strong MLCAPE will develop by this afternoon with values up to 2500-3000 J/kg. Some capping is noted on forecast soundings, but will quickly erode as lapse rates steepen just ahead of the front. Although the mid-level jet will be displaced somewhat to our north, deep layer shear of 40-45 kts will be more that sufficient to sustain storm organization. CAMS have storms initiating over eastern Iowa/northern Illinois by 2-3 pm, with activity approaching our northern counties sometime between 4-6 pm as it begins to congeal into more of a line segment. Environmental conditions will be favorable for severe storms with an enhanced risk (level 3 of 5) for numerous severe storms roughly near and west of I-55. Primary hazards with severe storms will be damaging winds potentially in excess of 75 mph and very large hail up to baseball size. The threat for tornadoes today is low, but nonzero and would be tied to any embedded supercells toward the beginning of the event in the enhanced risk area. Storms should start to lose steam around midnight as instability wanes, largely putting an end to the severe threat. A 25-30 kt LLJ nosing into central IL will likely continue to feed moisture into thunderstorms well into the early morning hours of Friday until the front pushes activity out a few hours prior to sunrise. Heavy rain is also a concern as forecast PWATs are expected to exceed 2 inches, suggesting storms could drop a lot of rain in a little amount of time. Antecedent dry conditions and high flash flood guidance should keep the flooding threat marginal, but if rainfall rates exceed flash flood guidance some issues could crop up. Drier air will filter in behind the front to close out the week as northwest flow becomes situated aloft. Although lower dewpoints will be seen, air temperatures will still be unseasonably warm both Friday and Saturday with values topping out in the middle to upper 80s. Hot and humid conditions ramp up once again by the second half of the weekend as an upper ridge builds east of here putting us under southwest flow. High temperatures Sunday through much of next week will be in the upper 80s to middle 90s, with heat indices in the upper 90s to near 100. An extended period of heat indices at these values could pose a threat for heat-related illness. The heat won`t be exiting anytime soon either as the Climate Prediction Center highlights at least a 60% chance or higher for above average temperatures through the remainder of the month. Precipitation chances going into next week will be tied to any upper waves lifting through southwest flow aloft. A more potent shortwave will spread through the Midwest states Sunday into Sunday night, possibly bringing our next chance for showers and storms. NMA && .AVIATION... (For the 12z TAFs through 12z Friday Morning) Issued at 648 AM CDT Thu Jun 13 2024 There is a small chance for a stray shower or storm west of the Illinois River this morning. Southwest winds become breezy later this morning with occasional gusts to 20 kts through the afternoon. A cold front will work through the area tonight, bringing a 60-80% chance for showers and thunderstorms. Confidence is high that thunderstorms will occur at or near all terminals, but timing is still a little uncertain. Because of this, a rather broad window for storms is mentioned with PROB30 groups for worsened conditions between 00-06Z. Winds shift to the north behind the front with speeds below 10 kts overnight. NMA && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$