Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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996 FXUS63 KILX 051851 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 151 PM CDT Fri Jul 5 2024 .KEY MESSAGES... - Scattered showers and storms return late Sunday through Tuesday, with the highest chances being Monday afternoon (40-60% chance). Severe thunderstorms and flash flooding are unlikely. - Temperatures will be seasonable over the next week, with highs in the 80s and lows in the 60s. Significant heat impacts are not expected during this time. && .DISCUSSION... Issued at 149 PM CDT Fri Jul 5 2024 A slow-moving low pressure system continues to drift SE over WI. The associated cold front has pushed into IN as of 120pm/1820z, with a few showers lingering near the IL/IN stateline at this time with the expectation that these will shift east in short order. Otherwise, brisk west-northwest winds prevail across the area with gusts of 20- 25 mph. Diurnal Cu is still expected to increase in coverage this afternoon/early evening (at least north of I-72) as forcing associated with the upper low pivots into the area. Regional radar shows scattered showers across IA where weak instability is present, and both sfc obs and mPING reports indicate rain reaching the sfc. Maintained a slgt chnc (15-20%) of rain in areas mainly north of Peoria. The diurnally-driven cloud cover should fade after sunset, resulting in mostly clear skies overnight. No weather impacts are expected on Saturday as the post-frontal airmass remains in place and weak sfc high pressure drifts across the Ozarks. Temperatures will be near to slightly below normal, with highs in the low to mid 80s. Into Sun, an amplified upper ridge will be centered over the western US, while a trough deepens over the central Plains and Beryl (presumably a Hurricane) approaches the S TX/N Mexico coasts. Locally, much of the area should stay dry Sun, although a few storms are possible (mainly west of the IL River) during the late evening/overnight hours (20-30% chance). Forecast soundings show modest instability (1000-1500 J/kg), but weak deep layer shear below 30 knots should limit storm organization. Better precip chances arrive on Mon (40-60% chance) and linger into Tues as a cold front moves through the CWA. Evaluating where Beryl will make landfall is beyond the scope of our local forecasting needs, but ensemble members are in strong agreement that the presence of the trough over the Plains/Midwest will tug the remnants of Beryl northward across interior E TX early next week. While Beryl may enhance moisture advection ahead of the front, even the fastest/northernmost ensemble members have Beryl far enough removed from our area that the truly tropical airmass does not interact with the front. Further, the presence of Beryl over the southern Plains actually appears to play a limiting role in the local severe storm potential from this early week trough. While the 500mb flow increases across central IL as the trough deepens (resulting in greater than 30 knots of deep layer shear), the flow pattern from Beryl disrupts the elevated mixed layer (EML) advection out of the SW US, and thus mid-level lapse rates/instability values are progged to be quite lackluster. Machine-learning guidance suggests that severe storm or flash flooding potential are both less than 5% Sunday through Tuesday. The probability of exceeding 0.5" of rain through Tuesday AM is just 15-30% (highest west of the IL River). Beyond Tues, most guidance has the cold front stalling south of our area, but given the typical model spread in placement at the Day 6+ range there is enough uncertainty to warrant keeping occasional slgt chnc (less than 25%) PoPs in the extended forecast. As the remnants of Beryl are absorbed into the main jet stream, most guidance has the remnants tracking south of the Ohio River, but this could be close enough to provide some additional forcing for showers/storms during the latter half of the work week. Throughout the period, temperatures are forecast to be seasonable, with highs in the 80s and lows in the 60s. Erwin && .AVIATION... (For the 18z TAFs through 18z Saturday Afternoon) Issued at 1159 AM CDT Fri Jul 5 2024 A cold front has pushed through central Illinois leaving a modest west to northwest breeze in its wake. Winds will gust to around 20 kt today, then diminish around sunset. VFR conditions are likely through most of the period, though some MVFR ceilings could spread south to near the I-74 corridor Saturday morning. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$