Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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016 FXUS63 KILX 100031 AFDILX Area Forecast Discussion...Updated National Weather Service Lincoln IL 731 PM CDT Thu May 9 2024 .KEY MESSAGES... - A threat for isolated lightning strikes will persist through the middle of this evening south of I-74. - A low-end lightning threat will accompany a line of showers crossing central Illinois from late Friday evening into early Saturday morning. - In the Monday-Tuesday time frame, there is a 20-40% chance of greater than a half inch of rainfall in 24 hours. Should this occur, one impact would be additional runoff into area rivers already running high. && .UPDATE... Issued at 731 PM CDT Thu May 9 2024 Latest surface map shows the frontal boundary has slipped south past I-72. A couple batches of showers are working their way through, one immediately behind the front, and another stretching from near Quincy to northern Indiana. This, and a third area of showers in southeast Iowa, is associated with an upper shortwave currently swinging southeast across Iowa. Latest high-res guidance suggests this Iowa batch of rain may hold together enough to warrant keeping some low PoP`s going past midnight across the Illinois River valley. Elsewhere, rain chances should gradually wane. No lightning has been observed as of late, though some heavier 40-50 dBZ showers were near Jacksonville this hour. Have lingered a mention of isolated thunder across the I-72 corridor for another hour or two. Geelhart && .DISCUSSION... Issued at 313 PM CDT Thu May 9 2024 A frontal boundary which was nearly stationary this morning has lifted northward slightly early this afternoon, with winds along I-74 backing somewhat in response. Around 250-750 J/kg of MLCAPE resides along a narrow axis from about Lincoln to Mattoon- Charleston where the sky has cleared somewhat, and we have seen a handful of showers reaching 40-50 dBZ or so with a few lightning strikes. The threat for lightning should persist no later than mid-evening as the frontal boundary pushes southward, MLCAPE decreases and the atmosphere stabilizes. A 500-mb short wave trough diving southward out of the upper Midwest helping to drive some of this afternoon and evening`s shower activity should pivot east into Indiana by early Friday morning. Weather during the day should be fairly quiet, with the next mid-level short wave and associated mid-level jet coming out of the upper Midwest on Friday evening. An associated weakening line of showers is forecast to move through central Illinois from northwest to southeast from late Friday evening through early Saturday morning, with around 100 J/kg of MUCAPE forecast by the HRRR indicating at least some probability of lightning especially Friday evening. Look for breezy northwest winds gusting to 20-30 mph on Saturday behind the departing short wave trough. Temperatures kick up a notch on Sunday under short wave ridging as a mid-level low moves out of the Colorado Rockies into the high Plains. This low is responsible for a chance of fairly widespread rainfall in the Monday-Tuesday time frame. The probability of SBCAPE > 250 J/kg and sfc-500 mb shear is below 5%, with severe weather probabilities low. Enough CAPE should be around to support some thunder, however. NBM probabilities show about a 20-40% chance of greater than a half inch of rain in a 24 hour period in the Monday-Tuesday window. Notable model variability exists in timing and strength of troughs beyond Tuesday. Though mid-range precip chances are included throughout Wednesday and Thursday, there`s a decent chance of at least one dry period occurring in that stretch. AAT && .AVIATION... (For the 00z TAFs through 00z Friday Evening) Issued at 605 PM CDT Thu May 9 2024 Band of MVFR to occasionally IFR ceilings has been sagging southward this evening, associated with a cold front that roughly extends from KIJX-KDNV. Lower visibilities have generally been associated with heavier showers immediately north of this front. General trend for the next several hours will be for ceilings to remain below 2,000 feet in most areas except for KPIA, where more of an increase to 5,000 feet is imminent. However, HREF guidance hints at some potential for IFR ceilings (30-50%) after 08Z. More of a general improvement is expected after 15Z. North/northeast winds overnight will generally trend more toward the northwest Friday morning. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$