Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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801 FXUS63 KILX 020502 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1202 AM CDT Thu May 2 2024 .KEY MESSAGES... - Level 1 risk of severe weather on Thursday has been expanded eastward to near I-55, though smaller scale features from leftover morning showers/storms may play a role in severe weather extent - Warmest period through this weekend will be on Thursday, with widespread highs in the mid 80s - Numerous chances for showers and thunderstorms over the next several days, though a significantly long dry period is hard to pin down right now && .UPDATE... Issued at 822 PM CDT Wed May 1 2024 This evening, a weak shortwave trough is noted over south central Missouri with scattered thunderstorms ahead of this feature south of the St Louis area. This wave will move east late this evening and overnight with some potential for a few showers and storms mainly near and south of I-70. 00Z ILX sounding indicated very dry air is in place below 800mb with an overall dry column (PWat 0.60 inches). Given the weak forcing, unfavorable diurnal timing, and dry antecedent conditions, convection will struggle as it moves into Illinois. HRRR is now calling for dry conditions through the night, though the RAP/NAMNest continue to show decaying showers reaching southern parts of the forecast area late this evening. Have lowered PoPs some to account for observed conditions and model trends, but maintain at least a slight chance mention in the SE this evening. Further NW across the Illinois River Valley, strengthening WAA will overspread the region late tonight and could bring another chance of showers and storms. Models have mostly slowed the arrival of precip until Thursday morning, so have lower PoPs accordingly. Deubelbeiss && .DISCUSSION... Issued at 307 PM CDT Wed May 1 2024 An active weather pattern will remain in place over the next week. In the shorter range, a broad upper low currently over northern Montana will gradually wobble eastward the next 36-48 hours, before finally lifting toward Hudson Bay on Friday. However, a stronger upper low moves onto the West Coast this weekend, then moves toward the central Rockies. The longer range synoptic models are in decent agreement with this feature eventually ending up in Montana or North Dakota as well. Thus, the overall upper pattern remains of Pacific origin. A lot of our weather will hinge on various waves ejecting ahead of, or circulating around, these features. Early afternoon surface map shows the wind shift with the front has settled south of I-70, while the drier air lags behind a bit. Dew points are down into the 40s west of I-55, but still linger in the 60s as far north as Mattoon and Paris. Radar mosaics show a cluster of storms developing over north central Arkansas, with the morning HiRes-ARW run handling it the best. Its solution shows a general development of scattered convection over central and southern Missouri this afternoon, extending eastward along the boundary toward early evening. Much of this is diurnally driven, and isolated PoP`s are in the forecast along it. However, more of a focus is expected after midnight, with elevated convection as the front lifts northward. The various high-res models have some disagreements with the eastward extent, and overall PoP`s after midnight haven`t been changed too much from previous, generally in the 30-40% range north of I-72. Any lingering showers from this elevated activity should be north of the forecast area by mid morning. Latest SPC Day2 outlook has expanded the level 1 (marginal) risk eastward to near I-55, though some complications arise if the overnight activity manages to form an MCS. We`ll fully be in the warm sector, with over 1,000 J/kg of surface based CAPE, though overall bulk shear parameters would only be more favorable west of the Illinois River. However, if the morning activity manages to get any boundaries in place, an uptick in activity is possible. For now, most daytime PoP`s will be confined to areas near and west of I-55, with activity spreading eastward in the evening. Rain chances linger into Friday, though primarily east of I-55. Going into the longer range, a shortwave is expected to track out of the Plains on Saturday. The day may start out dry, but scattered showers/storms are expected by afternoon as the front approaches. This front is expected to get hung up near or just south of the Ohio River later in the weekend, where we again get to monitor its northward return early next week as the upper low moves toward the central Rockies. Deterministic models suggest a period of dry weather Monday night and early Tuesday, though ensemble probabilities are harder to pin down a definite period. Earlier CSU machine learning probabilities suggested Tuesday as a potential day to watch for strong/severe storms, with timing still looking favorable, but it`s still way out there to get any real specifics. Geelhart && .AVIATION... (For the 06z TAFs through 06z Thursday Night) Issued at 1202 AM CDT Thu May 2 2024 Low pressure will lift from CO to WI through the period with a trailing cold front moving across central IL late Thursday evening and overnight. Light NE winds in place currently will veer to SE and begin gusting to around 20kt Thursday morning. Winds will continue to veer to SSE by around midday with gusts continuing in the 20-25 kt range. As the cold front approaches in the evening, scattered showers and storms are possible with winds turning NW behind the front. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$