Expires:No;;747904 FXUS63 KDVN 062251 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 551 PM CDT Mon May 6 2024 ...00Z AVIATION UPDATE... .KEY MESSAGES... - An organized line of storms is expected to move through the outlook area late tonight between 1 AM to 7 AM (west to east through the area). This system will pose a risk for damaging winds and isolated tornadoes. - For Tonight: The Storm Prediction Center has a Slight Risk for severe storms to the south and west of the Quad Cities with a Marginal Risk covering the rest of the area. - Isolated storms may redevelop Tuesday afternoon and evening, a few of which could be strong. - Scattered showers and storms remain possible on Wednesday before temperatures cool off late in the week. There is a Slight Risk for severe storms across the south on Wednesday with a Marginal Risk to the north. && .SHORT TERM /THROUGH TONIGHT/... Issued at 245 PM CDT Mon May 6 2024 Tonight into Tuesday Morning The forecast remains on track with a squall line expected to track through eastern Iowa, northeast Missouri, and northwest Illinois late tonight into early Tuesday AM. This complex of storms will cover a large spatial area so rain chances are high at 90-100% across the outlook area. The convection will initially develop across Kansas this afternoon/evening before growing upscale and tracking to the ENE into Missouri, Iowa, and Illinois tonight. Confidence has increased on the line of storms still packing a punch as it reaches the western to even central counties of the outlook area. While forecast MLCAPE is on the low side (250-1000 J/kg), low-level shear is high with 25+ kts in the lowest 1 km and 30-35 kts for 0-3 km. The strong environmental shear will help to balance the gust front on the leading edge of the convection, creating more concentrated lift and enhancing the potential for stronger storms. As for timing, the QLCS should reach the western counties between roughly 1 to 2 AM, central areas (near the Quad Cities) between 2 - 4 AM, and far eastern counties between 5 - 7 AM. SPC has expanded the Slight Risk for severe storms to the NE, now encompassing areas to the south and west of the Quad Cities, with a Marginal Risk for the rest of the forecast area. The primary threats are scattered damaging wind gusts around 60 mph, with a low potential for a few higher gusts over the far southwest counties. There is also an isolated QLCS tornado risk (5% within 25 miles of a point), highest in the aforementioned Slight Risk area. PWAT values near 1.25" are forecast with strong WAA forcing. Thus, rainfall on the order of 0.50" to 1" is likely for much of the area. Scattered showers and isolated storms could develop mid to late morning on Tuesday behind the departing QLCS, but these are not anticipated to pose a severe risk at this time. && .LONG TERM /TUESDAY THROUGH MONDAY/... Issued at 245 PM CDT Mon May 6 2024 The Upper Midwest is forecast to remain under general troughing or cyclonic flow aloft through the period. Flow aloft will be southwesterly a 500 MB through Wed/Thurs it becomes more northwesterly as the current storm system departs. This will allow a series of troughs and ridges in the northwest to move across the area into early next week. The trend for chances of showers and storms continues about every 24 to 36 hours. There will be periods of quiet weather in between. Timing on rain chances will likely vary over the next few days. Temperatures are trending below normal Friday through Sunday. The long term period begins Tuesday/Tuesday night with a closed 500 MB low over the northern PLains. At the surface, a cold front wiil move eastward across Iowa and Illinois through 00 UTC on Wednesday. A decaying MCS will likely be moving across our northwest Illinois counties at 12 UTC on Tuesday and exiting the area. Models show skies clearing quickly and do show some instability across the area ahead of or right behind the front which will lead to the risk of showers and storms during the afternoon. There could be some isolated severe storms with CAPE of 500 to 1000 J/KG and about 20 knots of 0 to 6 km shear. The main threats will be hail and damaging wind gusts. The amount of instability will depend on how quickly skies clear. On Wednesday, the closed 500 mb low will transition to an open wave with a positive tilt as it moves across the area. At the surface, a low is forecast to lift east northeastward from northwest Missouri into northeast Illinois or northern Indiana by 12 UTC Wednesday. This would bring the surface low and warm and cold fronts across the area during peak heating on Wednesday. SPC has a slight or level 2 out of 5 risk of severe storms on Wednesday for the area along and south of a Keosauqua to Iowa to Princeton Illinois with a Marginal or level 1 out of 5 risk for severe storms north of that line. Current model guidance shows the potentail for a high shear low CAPE event but it will depend on the track of the surface low and how much instability moves this far north. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 546 PM CDT Mon May 6 2024 A large complex of showers and thunderstorms remains on track to impact the terminals late tonight, with timing favored between around 08Z to 12Z. This will lead to periods of MVFR/IFR due to lower ceilings and reduced visibilities in heavier rain. The strongest cells could produce wind gusts near 50 kts from the WSW. There remains a low chance (20-30%) of a shower or storm developing Tuesday afternoon ahead of a front across eastern Iowa. However, latest CAMs are not in agreement on location of development or timing so have left a mention out of the TAF at this time. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Uttech LONG TERM...Cousins AVIATION...Speck