Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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286 FXUS63 KILX 171135 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 535 AM CST Mon Nov 17 2025 .KEY MESSAGES... - Rain will spread west to east across the area this evening into tonight, with a few showers lingering through tomorrow. Most locations will see rain amounts between a tenth and half an inch (80% chance). - The next opportunity for beneficial rainfall arrives late Thursday into Friday. There is a 30-60% chance (highest south) for rain amounts greater than 1 inch. && .DISCUSSION... Issued at 156 AM CST Mon Nov 17 2025 ***** SHOWERS TONIGHT INTO TOMORROW ***** Early Monday morning, water vapor satellite imagery reveals an upper level trough spinning in the Great Basin, with shortwave ridging ahead of it in the Great Plains and Mississippi River Valley. Both features will shift east today, resulting in increasing cloud cover and, by tonight, rain showers along and in advance of a warm front. This still isn`t looking like a significant rainfall event, but PWATs climbing to around 0.75-1.00" (around the 90th percentile of climatology) per HREF/REFS mean could still favor some pockets of half inch or greater amounts with the heaviest cells given the deep layer of "skinny" CAPE apparent in forecast soundings. Through tomorrow morning, HREF`s 10-90th percentile range for rain totals spans roughly a tenth to half inch area-wide, though slightly higher south of I-70. With the upper level shortwave passing overhead and the surface low nearby, NBM and HREF suggest low level clouds are going to stick around most or all of the day tomorrow, with perhaps a couple light showers as well (20-30% chance). In addition, north of the surface low, cool advection by east-northeast winds will confine temperatures to the 40s. The exact low track is not quite nailed down at this time, but we did knock a couple degrees off of NBM`s forecast which had highs in the mid 50s to mid 60s. Surface high pressure will settle back into the region in the wake of that system on Wednesday, resulting in drier weather conditions, though we`ll still have some clouds around as we find ourselves near the northern periphery of weak ridging across the Ohio and Tennessee Valleys. Temperatures will run near or slightly above seasonable normals with forecast highs in the low to mid 50s. ***** RAINY END TO THE WORK WEEK ***** At some point Thursday into Friday, a cutoff low in the Southwest will meander northeastward across the Southern/Central Plains and into the Mississippi Valley. The dipole in EOF1 for 500mb heights suggests the primary source of forecast variance among the Low Resolution Ensemble Forecast (LREF) system`s members is coming from differences in the speed at which this trough moves east into our area, so unsurprisingly the NBM (and hence our forecast) has a long duration of PoPs beginning as early as Wednesday night. In general, the global models and their respective ensembles have trended slower with the storm`s arrival and hence later with the onset of rain locally, but low confidence precludes any big PoP adjustments at this juncture. One shouldn`t be surprised, however, if even a portion of the day Thursday winds up being dry and most of any rain we receive falls between Thursday night and Friday evening. Chances for rain totals over 1 inch generally range from 30-60% across the area, with the highest chances south of roughly the I-72 corridor given a recent slight southward shift in the low`s track. We may also wind up with a couple rumbles of thunder across our southern counties, but severe weather potential still looks limited at this time given poor mid level lapse rates and cloud cover mitigating surface heating. Temperatures are looking mild on Thursday as warm and moist advection overspreads much of the region in advance of the trough; NBM advertises a 40-70% chance for highs over 60 degrees southwest of a roughly Macomb to Paris line. Friday could still be on the mild side, though prolific cloud cover and ongoing rain in much of the area may limit surface heating. Temperatures look to trend closer to seasonable normals over the upcoming weekend, though, as we get a weak push of cool advection behind that system. Bumgardner && .AVIATION... (For the 12z TAFs through 12z Tuesday Morning) Issued at 529 AM CST Mon Nov 17 2025 As surface high pressure shifts east into the Ohio Valley, winds will return from the southeast today at around 10-13 kt. Altostratus around FL070 will slowly shift east this morning, with a more notable increase in clouds this evening as a warm front approaches. That front will also spark some showers and possibly a thunderstorm overnight into Tuesday morning, though the probability of thunder (15%) was too low to warrant a prob30 group at this time. Ceilings will lower Tuesday morning, and HREF and NBM suggest probabilities for MVFR or lower ceilings will climb to 80-90% by roughly 15z/9am CST. Used FEW025 to hint at the increasing risk of an MVFR ceiling toward the end of the period. Bumgardner && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$