


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
710 FXUS63 KILX 161902 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 202 PM CDT Thu Oct 16 2025 .KEY MESSAGES... - Seasonably warm weather sticks around through Friday. Much cooler temperatures return early next week. - There is currently a low (5-15%) risk for severe weather to occur Saturday afternoon and evening in areas east of the Illinois River Valley. This risk is primarily driven by the potential for damaging thunderstorm winds. - Periods of heavy rain will occur Saturday afternoon and evening. There is currently a high (50-80%) chance that rainfall totals will exceed 1" in areas east of the Illinois River Valley; source: latest 13z NBM. && .DISCUSSION...(through next Thursday) Issued at 147 PM CDT Thu Oct 16 2025 |Synoptic Pattern| Afternoon water vapor imagery shows a closed, upper-level low over the Middle Rockies. Model guidance indicates this feature and its associated surface low will move into Manitoba by Friday morning, becoming occluded and slowing the cold front`s eastward progress. By Friday evening, the cold front will stretch from Minneapolis to Dodge City, Kansas. The front will accelerate significantly by Saturday morning as an upper-level jet maximum and a compact, mid-level shortwave trough move across the Southern Plains towards the Missouri Ozarks. A deepening surface low will develop across the Mid- Mississippi Valley Saturday, leading to increased winds and thunderstorm coverage within the warm sector. Gusty winds, much cooler temperatures, and lingering showers are then expected into Sunday morning before the surface low and cold front depart eastward. Monday will see a quick rebound in temperatures, driven by breezy southerly winds preceding yet another fast-moving frontal system. As this cold front moves across central Illinois on Tuesday morning, expect another round of scattered showers and thunderstorms. Seasonably cooler weather is expected by the middle of next week, with some forecast guidance indicating a trend toward frosty conditions by Wednesday morning. |Severe Weather Potential| By Saturday midday, a strong kinematic profile is expected to develop across our region. However, the thermodynamic environment preceding the cold front remains uncertain. Current ensemble guidance shows considerable spread in the timing and position of additional low-pressure development along the front. Specifically, the GEFS depicts a faster and more northerly low-pressure system, while the EPS and AIFS Ensembles suggest a slower and more southerly surface low. A GEFS-leaning scenario would bring more favorable moisture return and instability, and thus convective coverage, to a larger area of Illinois. Conversely, an EPS/AIFS Ensemble-leaning scenario would confine the better thermodynamic conditions and coverage to southern Illinois. At present, both scenarios are equally probable. We anticipate that high-resolution guidance from this evening`s 00z suite of CAMs will help to resolve this pattern. All that aside, the storm mode could shape up to be a messy one. A linear mode seems most likely across our CWA given the near- parallel orientation of the shear vectors with respect to the cold front. A stout LLJ veering in ahead of the front would point to primarily a damaging wind threat, with numerous reflectivity tags shooting up ahead of the line, and even some enhanced bowing segments within the line itself. Beyond Saturday, another sneaky episode of severe weather could evolve Tuesday morning as a cold front races into western Illinois. Current model guidance suggests a linear storm mode once again. This is due to a narrow band of favorable thermodynamics, accompanied by a robust/parallel shear profile, pushing into the area along the front. Moreover, the strong LLJ and steep low-level lapse rates ahead of the front could point toward a thin and kinky QLCS supportive of damaging winds and a brief tornado. |Beneficial Rainfall| A swift-digging, mid-level trough across the Southern Plains on Saturday will help draw Gulf moisture northward into the Lower- and Mid-Mississippi Valleys, in what could be the best synoptic rain event in some parts of central Illinois in over 10 weeks. A quick glance at climatology suggests that PWATs on Saturday (> 1.25") will be in the wettest 95th percentile for this time of year. That is an important note as we sift through all the deterministic and ensemble data, especially with respect to the upper and lower tails of the distribution. To that point, the latest operational run of the NBM (13z) suggests that the tails of the QPF distribution (10th -90th percentile) will range between 0.2" and 3" in areas east of the Illinois River. In other words, even in a bust scenario, we can expect about a 0.25" of rainfall. Obviously, the up shot is something more significant, and given the anomalous PWATs that we will have in place, and a mean wind (850-300 mb) roughly parallel to the surface front, it is not unreasonable that there could be localized rainfall amounts that approach the upper tail (90th percentile) of the QPF distribution. Again, we will eagerly await this evening`s 00z suite of CAMs to begin analyzing convective trends with respect to where the axis of heaviest rainfall might evolve, and how much. MJA && .AVIATION... (For the 18z TAFs through 18z Friday Afternoon) Issued at 1212 PM CDT Thu Oct 16 2025 Lingering MVFR clouds over eastern Illinois lifted to around 4000 feet by midday, and VFR conditions will prevail through Friday morning. Main aviation concern will be with winds, as they trend from southeast to south, then increase to 10-15 knots by mid morning. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$