Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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272 FXUS63 KILX 171945 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 245 PM CDT Tue Sep 17 2024 .KEY MESSAGES... - Well-above normal temperatures will continue through Friday, with highs in the upper 80s to near 90. Some modest cooling takes place later in the weekend, though nothing substantial. - Rainfall amounts are trending higher during the Saturday to Tuesday time frame across the Illinois River valley, though not likely enough to curtail the rapidly expanding drought conditions. && .SHORT TERM... (Through Thursday Night) Issued at 245 PM CDT Tue Sep 17 2024 Little change in our weather is expected through mid week, with the upper low over the western Carolinas drifting northeast and keeping the blocking pattern in place. Like today, strong mixing should allow for dew points to drop into the upper 40s or lower 50s Wednesday afternoon, near the NBM 10th percentile, so temperatures in the upper 80s will not feel overly hot. Going into Thursday, winds finally swing around to the south, as a skinny ridge of high pressure builds northeast from Texas to Michigan in response to an upper low in Utah lifting into Manitoba. This should allow for some modest recovery in dew points, but with the dry conditions over the last few weeks, the heat index should remain below air temperatures expected to be near 90. As the upper low moves into Canada, a trailing cold front will move across Illinois late Thursday night into early Friday. While this will bring the first decent rain chances in some time, they should mainly be limited to areas west of I-55. And, with the front battling a drier air mass, rainfall amounts should mainly be around a tenth inch or less. Geelhart .LONG TERM... (Friday through Next Tuesday) Issued at 245 PM CDT Tue Sep 17 2024 Morning model suite continues to show a trend toward a breakdown of the persistent blocking pattern during the second half of the forecast period. The upper low opens up somewhat, but still hangs around near the New England coast this weekend. Meanwhile, an upper low developing off the West Coast mid week will swing northeast out of the Desert Southwest. The front mentioned earlier is expected to get hung up late in the week, while the southwestern low moves into the central Plains. Ensemble guidance has been trending higher with rain chances and associated amounts for the Saturday-Tuesday time frame, with probabilities of over an inch of rain during this period around 30-40% west of the Illinois River valley per the time-lagged LREF. Rainfall for the first half of the month has generally been less than 5% of normal north of I-70 and not much better south of there. The warm and dry weather is steering toward rapidly expanding drought conditions, so any rainfall would be beneficial, but not likely enough in the short term. With this pattern shift, at least temperatures will return closer to normal beginning late in the weekend, though nothing especially cool. The CPC 8-14 day outlook continues to favor above normal temperatures. Geelhart && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1200 PM CDT Tue Sep 17 2024 VFR conditions expected the next 24 hours. Some high-based diurnal cumulus has formed southwest of KSPI and may produce some brief ceilings near 8,000 feet toward the beginning of the period. Wind flow will be out of the east, for the most part around 5 knots. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$