Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
608 FXUS63 KILX 130846 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 346 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. && .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 06z TAFs through 06z Thursday Night) Issued at 1140 PM CDT Wed Jun 12 2024 Mid-level clouds will be on the rise overnight as a decaying cluster of showers moves into western Illinois. While we have added VCSH to the KPIA terminal around 12z, confidence in rain reaching KSPI/KBMI is considerably lower. Despite the clouds and rain, VFR conditions are anticipated through Thursday afternoon. Attention then turns to Thursday evening as an organized line of showers and thunderstorms develops across portions of southeast Iowa and northern Illinois, gradually spreading southward into central Illinois prior to 00z. Enough signal exists within forecast models to introduce high confidence -TSRA across the regional terminals with this TAF cycle. MJA && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$