Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
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565 FXUS63 KDVN 021103 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 603 AM CDT Sat Nov 2 2024 .KEY MESSAGES... - An active pattern is expected tonight into Tuesday as an upper trough and very moist air mass interact to produce rounds of showers and thunderstorms (80-100%). Heavy rainfall amounts of several inches are likely by Tuesday morning. - Temperatures will trend warmer Sunday and Monday to above normal levels, before a cold front drops highs back into the 50s by mid next week. && .SHORT TERM /THROUGH TONIGHT/... Issued at 300 AM CDT Sat Nov 2 2024 Today and Tonight: Southeast return flow will develop today, albeit light, as high pressure shifts to the east over the Great Lakes. Steady warm air advection and plenty of sun to start the day will lead to above normal temperatures in the low 60s on average. Anticipate mainly dry conditions through the afternoon as the lower atmosphere will take time to saturate with dewpoints holding in the upper 30s to lower 40s. Increasing low to mid- level theta-e advection, on the eastern periphery of a 40-60 kt southerly LLJ, will eventually lead to the development of scattered showers and isolated thunderstorms tonight, becoming more likely after midnight. The highest precip chances are across the western portion of the outlook area, with a range from 100% in the west to 20-30% in the east. The showers/storms could produce narrow swaths of heavier rainfall with 0.50"+ possible over the west/northwest section of the forecast area by early Sunday AM. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 300 AM CDT Sat Nov 2 2024 A digging longer wave trof pushing into the west coast/Pacific NW will utilize rounding upper jet energy to continue to establish a large upper trough acrs the western Rockies by Sunday evening. This long wave will then look to dig acrs the western plains through Tue morning, with a squeeze play between it and southeastern CONUS ridging inducing an optimal southerly warm moist conveyor/LLJ feed off the western Gulf and up along and west of the MS RVR Valley. High amplitude steering southwesterlies will also shuttle occasional upper wave pieces up out of the trof base and acrs the eastern plains and into the upper MS RVR VAlley through Tuesday. These ejecting vort maxima/shortwaves and their lift will utilize the gulf moisture feed to produce rounds of rain (bouts of heavy rain look on target) for much of the mid to upper MS RVR Valley. Model averaged precipital water feed (PWATs) through Tuesday is showing very unseasonable PWATs near 1.5 inches streaming acrs the area by Sunday morning. Top-down saturation to full depth on Sunday, with fcst soundings then maintaining the deep vertical saturation with minor dry undulations aloft all the way through Tue morning. The extent of the southerly warm moist conveyor and fcst PWATs of an inch and a half are rare this time of year -- near the 99th percentile to climatological max! WPC has a Slight Risk of excessive rainfall across portions of the area from Sunday through Monday night, with the highest surges of rain expected Sunday night and again late Monday/Monday night. WPC rainfall potential at this juncture ranges between 2-4"+, heaviest swath near our area of concern from northeastern MO, to northeast IL through Tuesday. Recent rainfall softening the soil for more absorption, and the duration of "waves" of rainfall over 2 to 3 days will hopefully limit the overall flash flood threat. But the advertised widespread heavy amounts may eventually lead to slower paced areal flooding in low-lying, urban, and poor drainage areas by Monday/Monday night. As for the rivers, thinking there will be some substantial rises from current levels and may be near bankfull on tributary rivers in some of the harder hit basins. Confidence on a tributary or two reaching flood stage remains low and uncertain at this time. With eventual column saturation and fcst marginal mid layer lapse rates/MUCAPEs, the prospect for severe storms appears low at least through Monday during the day. Effective shear profiles are not bad ranging from 30 to 45 KTs, but the other parameters are not favorable. There may be a chance for a portion of a squall line to sweep acrs portions of the DVN CWA (probably the southeast third to half) Monday night into Tuesday morning, and SPC has introduced a Marginal Risk (level 1 of 5) for severe storms over the east-central to southeast portion of the outlook area. With the strengthening return flow and thickness increase/advection from the south, temps will be on the rise in the warm sector Sunday and especially Monday when there will be some 70s possible. Also with sfc DPTs in the 60s Monday, a muggy/humid feeling day more like later spring as opposed to November. Breezy conditions on Monday,and the LLJ is progged to ramp up to 50+ KTs at 4-5K FT AGL. Post-system cool down and some ridge infusion for a then needed dry period by mid to late week. Highs mainly in the 50s from Wed on into Friday. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 555 AM CDT Sat Nov 2 2024 VFR will prevail today with light southeasterly winds. Increasing high and mid clouds are expected later this afternoon into this evening, with chances for scattered showers and isolated thunderstorms holding off until tonight. Showers are likely late tonight/early Sunday morning at CID with lower chances for the other terminals to the east. Ceilings will gradually decrease to 3000-6000 ft AGL late in the period as the atmosphere continues to saturate. Held off on any thunder mention with this update due to low confidence. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Uttech LONG TERM...12/Uttech AVIATION...Uttech